IVth Semester Production Engineering

MODULE Lecture Notes on

I - II PE 204 Manufacturing Processes I
Casting, Welding, and Metal Forming

Casting
Dr. Joyjeet Ghose
Associate Professor,
Department of Production Engineering,
Birla Institute of Technology, Mesra
Joyjeet Ghose. 2020
Introduction to Manufacturing Processes
• Definition of Manufacturing
• The word manufacturing is derived from Latin:
manus = hand, factus = made
• Manufacturing is the economic term for making goods and services
available to satisfy human wants.
• Manufacturing implies creating value to a raw material by applying useful
mental and physical labour.
• Whether from nature or industry materials cannot be used in their raw
forms for any useful purpose.
• The materials are then shaped and formed into different useful components
through different manufacturing processes to fulfil the needs of day-to-day
work.
• Manufacturing is an industrial activity which converts the raw materials
to finished products to be used for some purpose (by altering its
geometry, properties and/or appearance) by application of physical and
chemical processes.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
CLASSIFICATION OF MANUFACTURING PROCESSES
Manufacturing processes can be grouped as:
 Casting, foundry or moulding processes.
 Forming or metal working processes.
 Machining (metal removal) processes.
 Joining and assembly
 Surface treatments (finishing).
 Heat treating
These groups are not mutually exclusive. For example, some finishing
processes involve a small amount of metal removal or metal forming. A laser
can be used for joining/metal removal/heat treating.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

CLASSIFICATION OF MANUFACTURING PROCESSES

Casting, foundry or
moulding processes
• Sand casting
• Investment casting
• Die casting
• Centrifugal Casting
• Continuous Casting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

CLASSIFICATION OF MANUFACTURING PROCESSES

Forming or metal working

processes
• Rolling
• Forging
• Extrusion
• Drawing
• Sheet metal works

Joining processes
• Welding (SMAW, TIG, MIG,
PLASMA, LBW, EBW etc.)
• Soldering
• Brazing
• Adhesive bonding
• Riveting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

CLASSIFICATION OF MANUFACTURING PROCESSES
Conventional Machining processes
• Turning
• Milling
• Drilling
• Shaping
• Grinding
• Broaching

Nonconventional Machining processes

• Electro chemical Machining (ECM)
• Electro Discharge Machining (EDM)
• Wire Electro Discharge Machining(WEDM)
• Abrasive Jet Machining (AJM)
• Ultrasonic Machining (USM)
• Liquid Jet Machining (LJM)
• Electron Beam Machining (EBM)
• Laser Beam Machining (LBM)
• Ion Beam Machining (IBM)
• Plasma Arc Machining (PAM)

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Manufacturing Processes and Manufacturing system
• Manufacturing system:
• A collection of operations and processes used to obtain a desired
product(s) or component(s) is called a manufacturing system.
• The manufacturing system is therefore the design or arrangement
of the manufacturing processes..

• Production system:
• A production system includes people, money, equipment, materials
and supplies, marketing, management and the manufacturing
system.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Production System - The Big Picture

Raw materials Manufacturing Manufacturing Finished

Process Process product

Manufacturing System

People, Money, Equipment, Materials and Supplies, Markets,

Management

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Syllabus
• Module 1: Sand Casting [10]
• Introduction to casting process and its importance, Patterns, pattern materials,
types of patterns, pattern allowances, molding and core sands, properties of
molding and core sands, mould and core making. Sand testing: grain fineness,
moisture content, clay content and permeability test, gating system and risers,
riser design, filling time problems, Sand casting defects; cleaning of casting
• Module 2: Casting Processes [5]
• Shell moulding; Investment casting; Evaporative Pattern casting; Vacuum
Casting; Die casting; Centrifugal casting; Continuous casting
• Module 3: Welding [8]
• Welding introduction and classification of welding processes, welding
terminology, general principles, welding positions, welding join types, welding
edge preparation.
• Gas welding and gas cutting, principles of oxy-fuel welding and cutting
• Arc Welding: Power sources and arc welding electrodes and its coating, working
principles and applications of SMAW, welding characteristic curve, GMAW,
GTAW, SAW; Modes of metal transfer in GMAW and their applications
• Soldering and brazing
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Syllabus
• Module 4: Welding Processes and NDT inspection [10]
• Working principles and applications of thermit welding, resistance welding; spot,
seam, projection and butt welding, plasma arc welding, electroslag welding,
Ultrasonic welding, electron beam welding (EBM), Laser beam Welding (LBW)
• Introduction to Non Destructive Testing (NDT) testing: Dye penetration testing,
eddy current testing, magnetic particles tesing, x-ray inspection, and ultrasound
testing
• Module 5: Forming processes [7]
• Introduction to recovery, recrystallization and grain growth; hot working and
cold working
• Rolling: Classification of rolling processes, rolling mills, products of rolling and
main variables
• Drawing: Drawing of rods, wires and tubes
• Forging: Open and closed die forging, forging operations, hammer forging, press
forging and drop forging
• Extrusion: Classification of extrusion processes, hot and cold extrusion
processes
• Sheet metal forming operations: Blanking, piercing, deep drawing, bending.
• Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Textbooks
• Serope Kalpakjian and Steven Schmidt , Manufacturing Processes for
Engineering Materials, Pearson Education, 6th Edition [T1]
• Mikell P. Groover, Fundamentals of Modern Manufacturing: Material. Processes,
and systems, 2nd Edition, Wiley India, 2007 [T2]
• P.N. Rao, Manufacturing Technology – Metal Cutting and Machine Tools,
McGraw Hill. [T3]
• P.N. Rao, Manufacturing Technology, Foundry, Forming and Welding, McGraw
Hill [T4]
• Hajra Choudhury, Elements of Workshop Technology–Vol.-II, Media Promoters
and Publishers [T5]

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Course Outcomes
• After the completion of this course, students will able to:

CO1 Interpret foundry practices like the basic principles in casting

and derive relationship in riser designing, cavity filling etc.
CO2 Select appropriate casting process for a given component
CO3 Identify the advantages and limitations of the various types of
joining processes and select the appropriate one according to the
application. Interpret the characteristic curves for welding
transformer.
CO4 Apply NDT techniques to identify various casting and welding
defects
CO5 Differentiate various metal forming processes such as hot and
cold working, rolling, forging, extrusion, sheet metal works and
drawing Processes.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting
• Casting takes advantage of the fact the liquid has fluidity, i.e. a
liquid can easily take the shape of the container.
• In a casting process, a solid material is first melted, heated to proper
temperature, and sometimes treated to modify its chemical
composition.
• The molten material, generally metal, is then poured into a cavity or
mould that contains it in the desired shape during solidification.
• Thus in a single step, simple or complex shapes can be made from
any material that can be melted.
• The resulting product can have virtually any configuration that the
designer desires.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Advantages of casting
• The most attracting feature of casting is that we can cast any shape
in one operation.
• It is possible to cast any material, be it ferrous or non-ferrous.
• Part of any size, shape and intricacy can be cast.
• The necessary tools required for casting are simple and inexpensive
(sand casting).
• Casting generally cools uniformly from all sides and therefore they
are expected to have no directional properties.
• Best suited for manufacturing of composite components.
• Some casting processes are capable of producing near net shape
products.
• Some casting processes are suitable for mass production.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Limitations of casting
• The dimensional accuracy and surface finish achieved by normal
sand-casting process would not be adequate for final application in
many cases.
• The sand-casting process is labour intensive to some extent and
therefore many improvements are aimed at it such as machine
moulding and foundry mechanization.
• With some materials it is often difficult to remove defects
• Limitations of mechanical properties.
• Safety hazards because of hot molten metals
• Environment issues

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Applications
• Cylinder blocks
• machine tools
• piston rings
• mill rolls
• Wheels
• water supply pipes
Sand Casting
• and bells etc

Investment Casting

Die Casting
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting Applications

Ductile Iron Brackets Tractor Gearbox Ductile Iron Auto Parts

Machined Ductile Iron Castings Automotive Casting

Cradle Chassis Brackets
of Vehicle
Source: http://www.iron-foundry.com/china-ductile-iron-castings.html
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting Applications

Ductile Iron Compressor Housing

Cast Iron Belt Pulley

Source: http://www.iron-foundry.com/china-ductile-iron-castings.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Applications
• Most casting processes requires machining of the casting.

FIGURE: Aluminum piston for an internal combustion engine. (a) As

cast; (b) after machining.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

 Classification of Casting
Casting

Expendable mould or
Multiple use moulds
Single use mould

Variations of
Permanent Mould
Multiple use patterns Single use patterns permanent mould Die casting Centrifugal Casting Continuous Casting
casting
casting

Hot chamber Die True Centrifugal

Sand casting Investment casting Slush Casting
casting Casting

Evaporative Pattern
CO2 moulding Low-Pressure Cold chamber Die Semi Centrifugal
/Lost Foam - Metal
casting Casting casting casting
Casting

Shell moulding Vacuum Permanent-

Centrifuging
casting mould Casting

Plaster-mould
Casting

Ceramic-mould
Casting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Classification of Casting
Casting

Expendable
Multiple use
Mould or Single
mould
use mould

Variations of
Single use Permanent Centrifugal Continuous
Reusable pattern Permanent Die casting
pattern mould casting casting casting
mould casting

Investment Hot chamber die True centrifugal

Sand Casting Slush casting
casting casting casting

Lost Low pressure Cold chamber Semi-centrifugal

CO2 Mould
foam/evaporative casting Die casting casting
casting
pattern casting

Shell mould Vacuum casting centrifuging

casting

Plaster mould
casting

Ceramic mould
casting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting terminologies
• The process starts with
construction of a pattern, an
approximate duplicate of the
final casting.
• The moulding material is then
packed around the pattern and
the pattern is removed to
produce a mould cavity.
• The flask is the box that
contains the moulding
aggregate.
• In two-part mould, the cope is
the name given to the top half
of the pattern, flask, mould, or
core.
• The drag refers to the bottom
half of any of these features.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting terminologies
• A core is a sand shape that is
inserted into the mould to
produce to produce internal
features of a casting, such as
holes.
• A core print is that region
added to the pattern, core, or
mould that is used to locate
and support the core within
the mould.
• The mould material and the
core then combine to form the
mould cavity, the shaped hole
into which the molten metal is
poured and solidified to
produce the desired casting.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting terminologies
• A riser is an extra void created in
the mould that will also fill with
molten metal.
• It provides a reservoir of material
that can flow into the mould
cavity to compensate for any
shrinkage that occurs during
solidification.
• The gating system is the network
of channels used to deliver the
molten metal to the mould
cavity.
• The pouring cup (pouring basin)
is the portion of the gating
system that initially receives the
molten metal from the pouring
vessel and controls its delivery to
the rest of the mould.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting terminologies
• From the pouring cup, the
metal travels down a sprue
(The vertical portion of the
gating system),
• then along horizontal channels,
called runners,
• and finally through controlled
entrances, or gates, into mould
cavity.
• Additional channels, known as
vents, may be included to
provide an escape for the gases
that are generated within the
mould.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting terminologies
• The parting line or parting surface is
the interface that separates the cope
and drag halves of a mould, flask, or
pattern and also the halves of a core
in some core making processes.
• Chaplets are used to support cores
inside the mould cavity to take care
of its own weight and overcome the
metallostatic forces.
• Chills are metallic objects which are
placed in the mould to increase the
cooling rate of castings to provide
uniform or desired cooling rate.
• The term casting is used to describe
both the process and the product
when the molten metal is poured and
solidified within the mould.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting terminologies

Mould Section and casting

nomenclature, (a) top view, (b)
front view

J S Campbell, Principles Of
Manufacturing Materials And
Processes

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting terminologies

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand mould

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

A Sand mould

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP
• Riddle: It is used for removing foreign materials such as nails,
splinters of wood etc. from the moulding sand. It is also known as a
sieve. It consists of a wooden frame fitted with a screen of standard
wire mesh at its bottom. Different types of riddles are denoted by
different numbers like 8, 10, 12 etc.
• Rammer: It is a wooden tool used for packing the sand into mould.
• Vent wire: It is a thin steel rod or wire having a pointed edge at one
end and a wooden handle or a bent loop at the other end. It is used
for making small holes called vents in the rammed sand moulds to
permit easy escape of gases and steam generated during cooling of
the heated metal.
• Trowel: Trowels are made of iron and are provided with a wooden
handle. They are available in many types and are used for making
joints and finishing flat surface of the mould.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP
• Slicks: They are available in many types, which vary in shape and
are used for repairing and provide finishing to mould surface and
edges after the pattern has been withdrawn.
• Lifters: They are used for patching deep sections of a mould and
removing loose sand from pockets of the mould. The lifters are
made of thin sections of steel of various width and lengths with one
end bent at right angles. The lifter is a finishing tool used for
patching deep sections of a mould and removing loose sand from
pockets of the mould.
• moulding board: It is smooth board on which the pattern and the
flask are placed during moulding.
• Bellows: They are used to blow loose sand out of the mould and are
used more frequently.
• Sprue pin: A sprue pin is wooden or metallic pin to make an
opening in the mould through which the metal is poured.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP
• Shovel: It consists of a square iron blade fitted with a D-shaped
wooden handle. It is used for transferring sand to the sand mixer and
pouring sand in the moulding flask.
• Strike off bar: It is a wooden or metallic bar having a true edge. It is
used for removing the surplus sand after ramming has been completed.
• Gate Cutter: It is a piece of sheet metal, which is used to cut opening
(gate) that connects the sprue with the mould cavity.
• Swab: It is made of hemp and used for applying water to the mould
around the edge of the pattern before removing the pattern from the
mould. This prevents the sand edges from crumbling when the pattern
is removed from the mould. A bulb swab has a rubber bulb to hold the
water and a soft hair brush at the open end.
• Ladle : They are used to receive molten metal from the melting
furnace and is used to pour the same into the mould.
• Crucibles: They are used as metal melting pots.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TOOLS AND EQUIPMENTS USED IN A FOUNDRY SHOP

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Basic factors common to all casting techniques
• A mould cavity must have the designed shape and size, and include
allowances for shrinkage. The mould material must be capable of
producing the engineered shape faithfully and not react with the
molten metal.
• Moulds can be produced for one-off castings, but economics make
it desirable to reuse moulds in some way, if possible. Permanent
moulds can be made of graphite or metals but are expensive.
• A suitable method of melting the alloy must be available; this
includes adequate temperature, satisfactory quality and quantity at
low cost.
• When the molten metal is poured, all gases must be able to escape
allowing the cavity to be filled and keeping the casting dense and
defect free; this is the reason for risers.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Casting Steps
• Preparation of the mould - includes pattern, core and gating system preparation.
• Melt metals
• Pour / force liquid into hollow cavity (mould)
• Cool / Solidify
• Remove
• Heat treatment if necessary
• Cleaning & Finishing.

Pattern
making Core making

Gating
Sand moulding systems

Melting Pouring Heat Cleaning &

Solidification Casting Inspection
Of Metal into mould Treatment Finishing

Shakeout and
Furnaces Removal of risers Additional heat Defects,
and gates treatment Dimensions

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable mould casting, using multiple use pattern: Sand casting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable mould casting, using multiple use pattern: Sand casting
• Sand casting is one of the older techniques and one of the most
commonly uses casting process.
• It uses sand as the primary moulding material.
• The sand grains are mixed with small amount of other materials such as
clay and water, to improve mould ability and cohesive strength, and are
then packed around a pattern that has the shape of the desired casting.
• The pattern is removed before pouring.
• For removal of the pattern, the mould is made of two or more pieces.
• The metal is then poured into the cavity through a gating system.
Gravity flow is the most common means of introducing the metal into
the mould.
• After solidification, the mould is broken and the finished casting is
removed. As the mould is destroyed a new mould must be made for
each casting.
• Therefore sand casting is expendable mould casting, using multiple use
pattern.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Pattern and pattern making
• The first step in sand casting is design and construction of pattern.
• Pattern is the principle tool during casting process.
• Pattern is a model of the casting to be cast, so constructed that it
may be used to form an impression called mould cavity in the
moulding sand. The mould cavity should be capable of producing
the required casting. When this mould cavity is filled with metal
and the metal is allowed to solidify, forms the required casting. The
pattern is therefore an approximate duplicate of the required casting
as it has core print and required allowances in order to produce the
required casting. Core prints
Allowances

Casting

Casting super imposed on

Pattern Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting terminologies
• Source NPTEL

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern materials
• Wood is the most commonly used pattern making material. Some
pattern materials are:
• Wood, cast iron, brass, aluminum, plastics, rubbers, plasters,
gypsum, and wax etc.
• The selection of pattern materials depends primarily on the
following factors:
– Service requirements, e.g. quantity, quality and intricacy of
casting.
– Type of production of castings and the type of moulding
process.
– Possibility of design changes.
– Number of casting to be produced.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Factors for selecting pattern materials
• The following factors assist in selecting proper pattern material:

– Quantity: No. of castings to be produced.

– Metal to be cast.
– Quality: Dimensional accuracy & surface finish.
– Shape, complexity and size of casting.
– Casting design parameters.
– Type of moulding materials.
– The chance of repeat orders.
– Nature of moulding process.
– Position of core print.
– Possibility of design changes

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern materials
• Requirements of good pattern material:
– Easily worked, shaped and joined.
– Light in weight.
– Strong, hard and durable.
– Dimensionally stable in all situation.
– Easily available at low cost.
– Repairable and reused.
– Able to take good surface finish.
– Resistant to wear and abrasion
– Resistant to corrosion, and to chemical reactions

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Comparative characteristics of metallic pattern materials

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern materials based on expected life

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Types of Pattern
• Single piece or Solid Pattern: This type of pattern is used only in cases where
the job is very simple and does not create any withdrawal problems. They are
relatively cheap to construct, but the moulding process is slow. Single piece
patterns are used for large castings of simple shape and for limited production.
• Split Pattern: These are used when moderate quantities of duplicate castings are
to be made. The pattern is divided into two segments along a single parting
plane, which will correspond to the parting plane of the mould. One half of the
pattern is moulded in drag and the other half in cope. The two halves of the
pattern must be aligned properly by making use of the dowel pins, which are
fitted, to the cope half of the pattern. These dowel pins match with the precisely
made holes in the drag half of the pattern.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Single piece or Solid Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Split Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Split Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Single piece or Solid Pattern and Split Pattern

Figure : Split pattern.

Figure. One piece pattern.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Single piece or Solid Pattern

Source: http://www.iron-foundry.com/hand-moulding-method.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Types of Pattern
• Match plate Pattern: A match-plate pattern is similar to a split pattern, except
that each half of the pattern is attached to opposite sides of a single plate. The
plate is usually made from wood or metal. This pattern design ensures proper
alignment of the mould cavities in the cope and drag and the gating system can
be included on the match plate. Match-plate patterns are used for larger
production quantities and are often used when the process is automated.

Source: http://www.custompartnet.com/wu/SandCasting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Match plate Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Match plate Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Types of Pattern
• Cope and Drag Pattern: A cope and drag pattern is similar to a match plate
pattern, except that each half of the pattern is attached to a separate plate and the
mould halves are made independently. Just as with a match plate pattern, the
plates ensure proper alignment of the mould cavities in the cope and drag. In
addition to the splitting the pattern, the cope and drag halves of the pattern along
with the gating and risering systems attached separately to the metal or wooden
plates along with alignment pins. Cope and drag patterns are often desirable for
larger castings, where a match-plate pattern would be too heavy and
cumbersome. They are also used for larger production quantities and are often
used when the process is automated.

Source: http://www.custompartnet.com/wu/SandCasting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Cope and Drag Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Types of Pattern
• Gatted Pattern: The gatted pattern is
used for mass production of small
casting. To save time, a number of
castings are produced in a single multi
cavity mould by joining a group of
patterns. Gatted pattern includes the
gating system in the pattern, as such
eliminates the time required to cut the
gating system by hand.

• Loose-piece Pattern: This type of

pattern is used when contour of the part
is such that withdrawal of the pattern
from the sand is not possible. Hence
during moulding, the obstructing part of
the contour is held as a loose-piece by
beveled grooves or pins or by a piece of
wire.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Gatted Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Gatted Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Gatted Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Loose-piece Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Loose-piece Pattern

Source: http://www.iron-foundry.com/hand-moulding-method.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Types of Pattern
• Sweep Pattern: Axis-Symmetrical moulds, particularly large in
size, are sometimes shaped by means of sweep patterns. The
sweep pattern consists of a board having a shape corresponding to
the shape of the desired casting and arranged to rotate about a
central axis.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sweep Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sweep Pattern

Source: http://www.iron-foundry.com/hand-moulding-method.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Types of Pattern
• Skeleton Pattern: It resembles from outside the shape of the
casting but otherwise is a simple wooden frame. This is a ribbed
construction with large number of square or rectangular openings
between ribs which forms a skeleton outline of the pattern to be
made. The frame work is fitted and rammed with clayed sand or
loam sand and a strike-off board known as strickle board is used to
separate the excess sand out of the spaces between the ribs so that
the surface is even with outside of the pattern.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Skeleton Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Skeleton Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Types of Pattern
• Follow Board Pattern: This type of pattern is adopted for those
castings where there are some portions which are structurally weak
and if not supported properly are likely to break under force of
ramming. Hence the board is modified as follow board to close fit
the contour of the weak pattern and thus support it during the
ramming of the drag. During the preparation of the cope, no follow
board is necessary because the sand which is compacted in the drag
will support the fragile pattern.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Follow Board Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Follow Board Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Follow Board Pattern

Source: http://www.brufnut.de/SS100/FORKS/FT_BR/ft_br.htm
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Types of Pattern
• Segmental Pattern: The segmental patterns are also known as part patterns.
Segmental patterns are sections of pattern arranged in such a way so as to form a
complete mould by moving the segmented pattern around the mould suitably.
These are generally applicable to circular work, like rings, wheels, rims, and
gears etc.
• Shell Pattern: Shell patterns are largely used for drainage fittings and pipe work.
This type of pattern is usually made of metal mounted on a plate and parted
along a central line, the two sections being accurately doweled together. The
short bends are usually moulded and cast in pairs. The shell pattern is a hollow
construction like shell. The outside shape is used as pattern to make mould while
the inside is used as a core box for making cores.
• Built-up Pattern: Built up patterns are composed of two or more pieces.
Patterns for special pulleys are built up of segments of wooden strips. Such
patterns are used to make intricate shapes.
• Lagged-up Pattern: When a pattern is so large or of such a form that it cannot
be made economically from a solid piece or when such a method would result in
a pattern of little strength or excessive weight, it is necessary to use a lagged or
staved pattern.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Segmental Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Segmental Pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multiple-part moulding

Source: http://www.iron-foundry.com/hand-moulding-method.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances
• Patterns are not made to the exact size as the desired casting for
several reasons. Such a pattern would produce casting which are
undersize. Allowances must therefore be made for shrinkage draft,
finish, distortion and rapping.
• Shrinkage Allowances:
• All most all cast metals shrink or contract volumetrically on cooling.
The metal shrinkage is of two types:
• Liquid Shrinkage: it refers to the reduction in volume when the
metal changes from liquid state to solid state at the solidus
temperature. To account for this shrinkage; riser, which feed the
liquid metal to the casting, are provided in the mould.
• Solid Shrinkage: it refers to the reduction in volume caused when
metal loses temperature in solid state. To account for this,
shrinkage allowance is provided on the patterns.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Shrinkage Allowances (Contd…):
• Following solidification, a casting continues to contract as it cools, the amount of
this contraction being as much as 2%. To produce the desired final dimensions,
the pattern must be slightly larger than casting. The exact amount of this
compensation depends on the metal that is being cast.
• Different metal has different shrinkages, therefore, there is a shrinkage rule for
each type of metal used in casting. Shrinkage allowances are often incorporated
into a pattern through the use of special shrink rules, measuring devices that are
larger than the standard rule by the desired shrinkage allowance.
• Brass- 1 feet measures 1 feet 3/16 inch

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances
• Draft Allowances: In many casting processes, the pattern contains surfaces
that are perpendicular to the parting line (parallel to the direction of pattern
withdrawal), the friction between the pattern and mould, or any horizontal
movement of the pattern during extraction would tend to damage the mould.
This damage would be particularly severe at the corners where the mould
cavity intersects the parting surface. By incorporating a slight taper, or draft,
on all surface parallel to the direction of withdrawal, this difficulty can be
minimized. As soon as the pattern is withdrawn a slight amount, it is free
from the sand on all surfaces, and it can be withdrawn further without
damaging the mould.
• The amount of draft is determined by the size and shape of the pattern, the
depth of the cavity, the method used to withdraw the pattern, the pattern
material, the mould material, and the moulding procedure.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Draft Allowances

Fig. Example of taper allowance

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances
• Suggested draft values for patterns

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances
• Finishing or Machining Allowances:
• If the casting process produces rough surfaces, than that have to be
machined to proper dimensions. Thus the extra amount of metal
provided on the surface to be machined is called machining or
finishing allowance.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Finishing or Machining Allowances

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances
• Distortion or camber Allowances:
• Same casting shapes require an additional allowance for distortion.
For example, the arms of a U shaped section may be restrained by
the mould, while the base of the U is free to shrink. This restraint
will result in a final casting with outwardly sloping arms. To
compensate for this distortion, the arms may be designed to
originally slope inwards, so that upon cooling they will distort to a
straight shape. This type of compensation is called Distortion or
camber Allowances
• Rapping Allowances
• When a pattern is rapped in the mould before it is withdrawn, the
cavity in the mould is slightly increased. In every cases where
casting must be uniform and true to pattern, rapping or shake
allowance is provided for making the pattern slightly smaller than
the actual size to compensate for the rapping of the mould.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Distortion or camber Allowances

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• Exercise: The casting shown in figure is to be made of plain carbon steel using
wooden pattern. Assume only shrinkage allowance to calculate the dimensions of
the pattern.

• From table for steel dimensions upto 600mm the shrinkage allowance is 21mm/m
• For dimension 200 the allowance is 200 x 0.021= 4.2mm
• For dimension 150 the allowance is 150 x 0.021= 3.15mm=3.2 mm
• For dimension 100 the allowance is 100 x 0.021= 2.1mm
• For dimension 80 the allowance is 80 x 0.021= 1.68mm=1.7mm?????
• The required pattern dimension is shown in the fig (b) above

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• Exercise: For the previous example, if an aluminium pattern is use for casting.
The aluminium pattern is made using a wooden pattern (master pattern).
Calculate the dimensions of the master pattern. Consider only the shrinkage
allowance

• Fig (b) shows the dimensions of the aluminium pattern

• From table for steel dimensions upto 600mm the shrinkage allowance is 21mm/m
and for aluminium the shrinkage allowance is 13mm/m . Therefore the total the
shrinkage allowance is 34mm/m
• For dimension 200 the allowance is 200 x 0.034= 6.8mm
• For dimension 150 the allowance is 150 x 0.034 = 5.10mm
• For dimension 100 the allowance is 100 x 0.034 = 3.4mm
• For dimension 80 the allowance is 80 x 0.034 = 2.72mm
• Lecture
The notes
required pattern dimension is shown in the fig (c) above
on PE204 Manufacturing Processes I, Joyjeet Ghose
Pattern making allowances examples
• Example: Again from the previous example, what will be the pattern dimension if
all the surfaces of the casting need to be machined?
• Let us decide to cast the job horizontally and use a solid pattern for this casting.
• For dimension 200 the allowance is 200 +5.5+5.5= 211mm
• For dimension 150 the allowance is 150 +3+3= 156mm
• For dimension 100 the allowance is 100 +3+6= 109mm (note: 6 mm for cope side
allowance)
• For dimension 80 the allowance is 80 - 2x3== 74mm

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• Example : Grey cast iron castings of dimension 80 mm are to be made in a metal
mould made of aluminium alloy. The metal mould is to be made using a wooden
pattern. Determine the correct dimension of the wooden pattern considering the
solidification contraction only.
• Solution. Here the wooden pattern must have a double shrinkage allowance for
the shrinkage of metal mould (aluminium) and the casting (cast iron).
• Allowance for aluminium = (80 mm) x (1.20/100 mm/mm) = 0.96 mm
• Allowance for cast iron = (80 mm) x (0.80/100 mm/mm) = 0.64 mm
• Therefore, total shrinkage allowance = 0.96 + 0.64 = 1.60 mm
• Hence, the dimension of the wooden pattern would be = 80 + 1.60 = 81.60 mm

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• Exercise : The casting shown is to be made in cast iron using a wooden pattern.
Assuming only shrinkage allowance, calculate the dimension of the pattern. All
Dimensions are in Inches (Source NPTEL)

Solution 1
The shrinkage allowance for cast iron for size up to 2 feet is o.125 inch per feet (as
per Table 1)
For dimension 18 inch, allowance = 18 X 0.125 / 12 = 0.1875 inch » 0.2 inch
For dimension 14 inch, allowance = 14 X 0.125 / 12 = 0.146 inch » 0.15 inch
For dimension 8 inch, allowance = 8 X 0.125 / 12 = 0.0833 inch » 0. 09 inch
For dimension 6 inch, allowance = 6 X 0.125 / 12 = 0.0625 inch » 0. 07 inch
The pattern drawing with required dimension is shown below:

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
Table 1 : Rate of Contraction of Various
Metals
Material Dimension Shrinkage allowance
(inch/ft)
Grey Cast Iron Up to 2 feet 0.125
2 feet to 4 feet 0.105
over 4 feet 0.083
Cast Steel Up to 2 feet 0.251
2 feet to 6 feet 0.191
over 6 feet 0.155
Aluminum Up to 4 feet 0.155
4 feet to 6 feet 0.143
over 6 feet 0.125
Magnesium Up to 4 feet 0.173
Over 4 feet 0.155

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• Exercise : The casting shown is to be made in cast iron using a wooden pattern.
Assuming only machining allowance, calculate the dimension of the pattern. All
Dimensions are in Inches. (NPTEL)

• Solution 2
The machining allowance for cast iron for size, up to 12 inch is 0.12 inch and from
12 inch to 20 inch is 0.20 inch (Table 3)
For dimension 18 inch, allowance = 0.20 inch
For dimension 14 inch, allowance = 0.20 inch
For dimension 8 inch, allowance = 0.12 inch
For dimension 6 inch, allowance = 0.12 inch
The pattern drawing with required dimension is shown in Figure below

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples

Table 3 : Machining Allowances of Various Metals

Dimension Allowance
Metal
(inch) (inch)
Up to 12 0.12
Cast iron 12 to 20 0.20
20 to 40 0.25
Up to 6 0.12
Cast steel 6 to 20 0.25
20 to 40 0.30
Up to 8 0.09
Non ferrous 8 to 12 0.12
12 to 40 0.16

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• A job shown in the Figure is to be made of steel by casting process. The mould
for this job is made from a wooden pattern. Determine the dimensions of the
wooden pattern. Assume machining allowance of 2 mm on each side, shrinkage
allowance of 2% and a taper allowance of 1 degree.

• Solution
• Step-1: Machining Allowance
• It is given that machining allowance of 2 mm on each side is to be given. Thus,
each side is increased by 2 mm resulting in the basic dimension of the pattern as
shown in Figure (a). The required casting is shown with dotted lines.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• Step-2 : Taper Allowance
• We decide to cast the job horizontally and use a solid pattern for this casting. For
this design, the draft allowance is to be provided on the vertical sides (24 mm
long). Considering the given taper allowance of 1 degree, the side view of the
pattern would be as shown in Figure (b).
• The taper allowance value x is calculated from the geometry of the Figure (b) as
• x = 24 tan 1 = 0.419 mm.
• Thus, thetop surface dimension is increased to provide for draft allowance from
54 x 84 mm to 54.838 x 84.838 mm.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• Step-3 Shrinkage Allowance:
• Given shrinkage allowance is 2%. Now, the dimensions of pattern are increased
by 2% on all sides.
• That is, dimension 54 mm will become
• 54 + (54*2)/100 = 55.08mm or 55.1mm
• The dimension 54.838 will become 54.838 + (54.838*2)/100 = 55.9mm
• Similarly, all other dimensions are calculated and the final dimensions of the
pattern are shown in Figure

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• A job shown in Figure is to be made from steel by casting process. The mold for
this job is made from wooden pattern. Determine the dimensions of the wooden
pattern assuming machining allowance of 3 mm on each side, shaking allowance
of 1 mm on length and width, shrinkage allowance of 3%

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• Step-1 : Machining Allowance: Since given machining allowance is 3 mm on
each side, add 3 mm on each side of the part shown in Figure. The dimensions of
the pattern after machining allowance will be:
• L = 80 + 2 x 3 = 86 mm
• W = 40 + 2 x 3 = 46 mm
• H = 30 + 2 x 3 = 36 mm
• The dimensions of the pattern after adding machining allowance are shown in the
following figure .
• Step-2 : shrinkage allownce :The shrinkage allowance of 3% is added to all the
dimensions of the pattern shown in Figure. Dimension of the pattern after
providing shrinkage allowance of 3% will be:
• L = 86 + 86 x 3/100 = 88.58 mm,
• W = 46 + 46 x 3/100 = 47.38 mm
• H = 36 + 36 x 3/100 = 37.08 mm

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pattern making allowances examples
• Step -3 : Shaking Allowance : Given shaking allowance is 1 mm on length and
width.
• Recall that, shaking allowance is a negative allowance.
• Hence, 1 mm has to be reduced from the calculated values of length and width
side.
• Students are advised to note that the height of the pattern doesn’t require any
shaking allowance.
• Therefore, final dimension of the pattern will be:
• L = 88.58 – 1 = 87.58 mm
• W = 47.38 – 1 = 46.38 mm
• H = 37.08 mm

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Master patterns:
• Master patterns are used for preparing the moulds for metal castings which are later used
as patterns for further moulding work, called metal patterns. The master patterns are
accurately finished wooden patterns, which carry double shrinkage allowance and the
required machining allowance. For example, an alluminium pattern is to be made which is
to be used further for making moulds for brass castings. The alluminium pattern should,
obviously, be larger than the desired brass casting by an amount equalto shrinkage that
will take place during solidification ofthis casting. For making this alluminium pattern a
wooden pattern is to be used which should be larger than the alluminium pattern by an
amount equal to the alluminium shrinkage, added with proper machining allowance for
finishing the alluminium casting. Mathematically, it can be represented thus :
Let Sb represent the size of the desired casting in brass. And Let Sa represent the size of
aluminum pattern. And Let Cb represent the contraction allowance for brass.
Then Sa=Sb+Cb
• Again, let S represent the size of the master pattern. And let Ca represent the contraction
allowance for aluminum. Also let Am represent the machining allowance required
to finish the aluminum casting to the required size of
pattern and to give smooth surface finish.
• Then S = Sa+Ca+Am = Sb+Cb+Ca+Am , Or
• Size of master pattern = Size of the final casting to be Made + shrinkage allowance for the
material of final casting + shrinkage allowance of the metal of which the pattern is to be
made + Finishing allowance for the metal pattern.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Moulding Sands
• Silica Sand Grains:
– moulding sand contains 80 to 90 % silica. Silica in the form of
granular quartz, itself a sand, it is the chief constituent of moulding
sand. They impart refractoriness, chemical resistivity and
permeability to the sand. The sand grains may vary in size from few
micrometers to a few millimeters. The shape of sand grains may be
round or angular. Silica sand normally contains some oxides of
aluminium, sodium, magnesium and calcium as foreign material.
• Moisture/Water:
– Clay acquires its bonding action only in the presence of required
amount of water (1.5 to 8 %). When water is added to clay it
penetrates in to the mixture and forms a microfilm, which coats the
surface of each flake.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Moulding Sands
• Clay:
– Clay can be defined as natural earthy material that becomes plastic
when mixed with water. Clay consists of two ingredients: fine silt and
true clay. Fine silt is a foreign material or mineral deposit and has no
bonding power, whereas true clay imparts the necessary bonding to
the moulding sand. Its purpose is to impart necessary bonding
strength to the mould sand so that the mould does not loose its shape
after ramming. moulding sand contains about 5 to 20 % clay.
– The most popular types of clay used are: Kaolinite or Fireclay
(Al2O32SiO22H2O) and Bentonite (Al2O34SiO2H2OnH2O).
– Fireclay has higher melting point than Bentonite. However, Bentonite
can absorb more water which increases its bonding power. Bentonite
also has better permeability.
– Bentonite is of two types: Calcium ion based bentonite and sodium
ion base bentonite. Sodium ion based bentonite provides better
bonding properties.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Moulding Sands
• Additives: Materials other than basic materials are also added to the
moulding sand for improving existing properties. These are:
– Facing Materials: Facing materials are used to get smoother and
cleaner surfaces of castings and helps easy peeling of sand from the
casting surface during shake out. These are:
– Coal dust: Coal dust or sea coal is finely grounded soft coal
(pulverized coal). It tends to obtain smoother and cleaner surface and
reduces the adherence of sand particles to the casting. It also
increases hot and dry strength of the mould.
– Silica flour: It is very fine ground silica. It improves surface finish of
the casting.
– Cushion Materials:
– Cushion materials burn when molten metal is poured and thus give
rise to space for accommodating the expansion of silica sand at the
surface of mould cavity. E.g. wood flour, cellulose, and cereals.
– Wood flour: It is ground wood particles or other cellulose materials.
– Cereals: Cereals are finely ground corn flour.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Moulding Sands

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Classifications of moulding Sand: According to the nature of its origin
• Natural Sand: Natural sand is also called green sand, is taken
from riverbeds or is dug from pits. Natural sand contains sufficient
amount of binding materials (Clay) in it so that it can be used
directly.
• Advantages:
–Natural sand maintains moisture content for a long time.
–They are cheap.
–The time for mixing the binder is saved.
–No extra equipment for mixing the sand and the binder.
• Disadvantages:
–They are less refractory than synthetic sands because of
impurities present.
• Applications: Light castings, Mechanized production of casting
with few cores.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Classifications of moulding Sand: According to the nature of its origin
Synthetic Sand: Synthetic sands are basically clay free high silica
sands. They are mixed with desired amount of clay and water to
develop required moulding properties. It is used for steel castings.
• Advantages:
–High permeability and refractoriness.
–mouldability with less moisture.
• Disadvantages:
–It is more costly.
–It needs extra time, equipment and men to prepare the sand.

• Applications: Heavily cored castings, Mechanized production,

High pressure moulding..

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Classifications of moulding Sand: According to the nature of its origin
Special Sands: Special sand is ideal in getting special characteristics, which
are not ordinarily obtained in other sands. Zircon, olivine, chamotte,
chromite and chrome-manganese are often used as special sands.
• Zircon sand: Zircon sand is zirconium silicate (ZrSiO4). This sand has
low thermal expansion, high heat conductivity, greater density and high
refractoriness. These sands are used for bronze casting, alloy steels-
chrome steels and manganese steels casting.
• Olivine sand: This is orthosilicate of iron and manganese (MgFe)O.SiO2.
It has high density, conductivity and refractoriness. It is used for non-
ferrous, steels and intricate casting.
• Chamotte sand: This is produced by calcining high-grade fire clay at
about 11000C and crushing it to the required grain size. It is much
cheaper than zircon and olivine. It is used for heavy steel Casting.
• Chromite and Chrome-magnesite: It has refractoriness, high density and
chilling power. It is useful where chilling tendency is to be increased to
control solidification.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Classification of moulding Sand: Acc. to their initial conditions and use
• Green Sands: Foundry sand containing moisture is known as green
sand. It is a mixture of silica sand with 18 –30 % clay, having total
water from 6-8%. This is suitable for moulding purposes without any
further conditioning. Green sand is generally used for casting small
or medium sized moulds.
• Dry Sands: Sands free from moisture are called dry sands. It
possesses greater strength than green sand and can be used for
making larger castings.
• Loam Sands: Loam sands are a mixture of sand and clay (50%). It is
used for making larger castings such as large cylinders, paper rolls.
• Facing Sands: Facing sand forms the face of the mould. It is used
directly next to the surface of the pattern and it comes in contact with
the molten metal when the mould is poured. Consequently it is
subjected to the severest conditions and must possess high strength
and refractoriness. Facing sand is composed of dry silica and facing
materials.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Classification of moulding Sand: Acc. to their initial conditions and use
• Backing Sands: It is the sand, which backs up the facing sand and
to fill the rest of the flask. It is the floor sand already been used.
• Parting Sands: Sand employed on the faces of the pattern before
moulding is called parting sand. The parting sand contains dried
silica, and burnt sand. Parting sand is used to avoid sticking of the
green sand to the pattern.
• Core Sands: Sands used for making cores are called core sands.
This is silica sand mixed with core oil, which is composed of
linseed oil, resin, light mineral oil and other binding materials.
• System Sands: In mechanical foundries where machine moulding
is employed a so called system sand is used to fill the whole flask.
In mechanical sand preparation and handling units no facing sand
is used.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Properties of moulding Sand
• Permeability or Porosity: Molten metal always contains a certain
amount of dissolved gases, which are evolved when the metal
solidifies, also when the molten metal comes in contact with
moisture sand, generates steam and water vapour. If these gases and
water vapour do not find passage to escape completely through the
mould they will form gas holes and pores in the casting. The ability
of the sand to allow the gas to pass through it is called permeability.
It depends on the size and shape of grains, moisture content and
degree of ramming.
• There are four factors that control the permeability of foundry sand:
(1) fineness of the sand grains, (2) shape of the sand grains, (3) the
amount and type of binder, and (4) the moisture content.
Permeability is expressed as a number that increases with an
increasing openness of the sand.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Properties of moulding Sand
• Plasticity and Flowabilty: This refers to the ability of the moulding
sand to acquire a predetermined shape under pressure and retain the
same when the pressure is removed. This will increase with clay and
moisture content.
Adhesiveness: moulding sand particles should stick to the surface of
the moulding boxes. This enables the mould to retain in a box
during handling.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Properties of moulding Sand
• Cohesiveness: Cohesiveness is the ability of the sand particles to
stick to each other. Lack of this property would result in breaking of
the mould when molten metal is poured. This depends on grain size
(decreases with grain size) and clay content (increases with clay) of
sand.
• Green Strength: It is the strength of the sand in green or moist
state. A mould with adequate green strength will not disturb or
collapse even after removing the pattern from the mould box in the
absence of green strength, dimensional stability and accuracy
cannot be obtained.
• Dry strength: It is the strength of the moulding sand in dry
condition. A mould should possess adequate dry strength to
withstand erosive force and pressure of the molten metal.
• Hot Strength: It is the strength of the mould cavity above 100  C.
If hot strength is inadequate the mould is likely to enlarge, break or
get cracked.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Properties of moulding Sand
• Refractoriness :The capability of the moulding sand to withstand the
high temperatures of the molten metal without fusing is known as
refractoriness.
• Collapsibility: It is the property of the moulding sand that permits it to
collapse easily during its knockout from the casting.
• Coefficient Of Expansion: moulding sands should possess low
coefficient of expansion. Otherwise mould might crack. moulding sands
should possess low coefficient of expansion. Otherwise mould might
crack.
• Fineness: Finer mould sand resists metal penetration and produces
smooth casting surface. Fineness and permeability is opposite to each
other. Hence these should be balanced for optimum result.
• Bench Life: It is the ability of mould sand to retain its properties during
storing, handling or while standing.
• Chemical Reactivity: The moulding sand should not react chemically
with molten metal, otherwise the shape of casting will be disturbed and
smooth surface will not be obtained.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Permeability of moulding sands
• There are four factors that control the permeability of foundry sand: (1) fineness
of the sand grains, (2) shape of the sand grains, (3) the amount and type of
binder, and (4) the moisture content. Permeability is expressed as a number that
increases with an increasing openness of the sand.
• 1. Grain Fineness. Grain fineness is an indication of the grain size of the sands.
It is expressed as a number that tells a moulder if he has a fine sand, made up
largely of very small sand grains, or a coarse sand, composed mainly of large
sand grains. The permeability of the coarse sand is very high. As the sand grains
become smaller, the permeability decreases rapidly. This decrease is due to the
smaller voids or openings between the individual sand grains for the fine sand.
Coarse sand grains have the same general size relation to fine sand grains as
basketballs have to marbles.
• Shape of the Sand Grains. There are two primary shapes of sand grains, angular
and rounded. There are many degrees of roundness or angularity between the two
extremes. Angular grains can be compared to crushed stone. There are sharp
edges and corners on the grains. The rounded sand grains have the appearance of
beach pebbles that have been rounded by the action of the sea. Sharp angular
sand grains cannot pack together as closely as rounded sand grains. As a result,
sand with angular grains have a higher permeability than sands with rounded
grains.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Permeability of moulding sands

Figure a. Permeability as affected by the grain

size of sand.

Figure b. The effect of sand grain shape on permeability

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Permeability of moulding sands
• 3. Binder. The amount and type of binder also have an effect on the permeability
of foundry sand. The effect of increasing amounts of bentonite on permeability is
shown in figure a. The permeabilities are shown for moisture contents of 2 and 4
percent. With 2 percent moisture, the sand shows a rapid decrease in permeability
with increased bentonite content. Sands containing 4 percent moisture show a
fairly constant permeability after 4 percent bentonite is reached. This type of
information indicates that 4 percent of moisture in this particular sand would
produce the best permeability over a range of bentonite contents. The type of
binder also affects permeability, as shown in figure b.

Figure a. Permeability as affected by the Figure b. The effect of bentonite and fireclay
amount of binder. on permeability.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Permeability of moulding sands
• 4. Moisture Content. The effect of moisture content on permeability was shown
in figures. Low permeability at very low moisture content is caused by the dry
clay particles filling the spaces between the sand grains. Figures a and b both
show an increase in permeability to a maximum value, and then a decrease with
further additions of water. The increase in permeability is produced when the
moisture causes the clay particles to agglomerate or stick together. This action is
similar to the addition of water to dust to form a firm piece of soil. When water is
added in excess of the amount to produce this sticking together, the excess water
begins to fill in the holes between the sand grains and as a result, the permeability
goes down. This action is similar to the addition of water to a firm soil to produce
mud.

Figure a. Permeability as affected by sand Figure b. The effect of sand grain shape on
fineness and moisture. permeability
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Sand conditioning / Sand preparation
• Proper sand conditioning accomplishes uniform distribution of
binder around the sand grains, controls the moisture content,
eliminates foreign particles, and aerates the sand so that it flows
readily around and takes up detail of the pattern.
• The basic steps are:
– The first step is to remove all foreign and undesirable matters
such as nails, fins, hard sand lumps from the moulding sand.
– The second step is mixing of its ingredients, proper amounts of
pure sand, clay and other additives are mixed and water is
spread over the entire volume. Muller is used for mixing all the
ingredients of sand. Muller is a device which kneads rolls and
stirs the sand.
– In the third step, the sand is passed through a mechanical aerator
to separate sand grains into individual particles. It is performed
to increase the flowability.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Sand conditioning / Sand preparation

Batch Mueller

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand moulding machines:
• Vertical flaskless moulding
• Sandslinger
• Impact moulding
• Vacuum moulding

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand moulding machines:
• Hand ramming: is the simplest method of compacting sand. To increase the
rate, pneumatic rammers are used. The method is slow, the sand is rammed in
layers, and it is difficult to gain uniform density.
• squeezing machines: More uniform results and higher production rates are
obtained by squeezing machines. Hand-operated squeezers were limited to small
moulds and are obsolete; air-operated machines permit an increase in the
allowable size of moulds as well as in the production rate. These machines are
suitable for shallow moulds. Squeezer moulding machines produce greatest sand
density at the top of the flask and softest near the parting line of pattern. Air-
operated machines are also applied in vertical moulding processes using flaskless
moulds. Horizontal impact moulding sends shock waves through the sand to pack
the grains tightly.
• The sand is rammed harder at the back of the mould and softer on the pattern
face. In other words sand has greatest density at the surface where pressure is
applied to sand and sand density decreases progressively towards the pattern.
• moulding force (Mf) = P (π. d2/4)-W
Where, P – Pressure in squeeze cylinder
d – Piston diameter
W – Weight of flask pattern and sand
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Sand moulding machines:
• In jolt moulding machines the pattern is placed on a platen attached to the top of
an air cylinder. After the table is raised, a quick-release port opens, and the
piston, platen, and mould drop free against the top of the cylinder or striking
pads. The impact packs the sand. The densities produced by this machine are
greatest next to the parting line of the pattern and softest near the top of the flask.
This procedure can be used for any flask that can be rammed on a moulding
machine. As a separate unit, it is used primarily for medium and large work.
Where plain jolt machines are used on large work, it is usual to ram the top of the
flask manually with an air hammer.
• Jolt-Squeeze machine combines in single machine the operating principles of
the jolt and squeeze machines. Combination of jolting and squeezing produces
beneficial compaction effects on sand density and thus a more uniform hardness
throughout the mould is attained. A jolt-squeeze machine makes use of match
plate moulding. Jolt squeeze machines use both the jolt and the squeeze
procedures. The platen is mounted on two air cylinders: a small cylinder to jolt
and a large one to squeeze the mould. They are widely used for small and
medium work, and with match-plate or gated patterns. Pattern-stripping devices
can be incorporated with jolt or squeezer machines to permit mechanical removal
of the pattern. Pattern removal can also be accomplished by using jolt-rock over-
draw or jolt-squeeze-rollover-draw machines.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Sand moulding machines:

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Jolt Squeeze moulding Machine

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand moulding machines:
• The sand slinger is the most widely applicable type of ramming machine. It consists of an
impeller mounted on the end of a double-jointed arm which is fed with sand by belt
conveyors mounted on the arm. The impeller rotating at high speed gives sufficient
velocity to the sand to ram it in the mould by impact. The head may be directed to all parts
of the flask manually on the larger machines and may be automatically controlled on
smaller units used for the high-speed production of small moulds. The sand slinger
consists of a base, a sand bin, a bucket elevator, a swinging or movable arm, a belt
conveyor and the sand impeller. Prepared sand lying in the sand bin is picked up by the
elevator buckets and is dropped on to the belt conveyor which takes the same to the
impeller head. Inside the impeller head, rapidly rotating cup shaped blade picks up the
sand and throws it downward into the moulding box as a continuous stream of sand with
machine gun rapidity and great force.
• The sand is discharged into the moulding box at a rate of 300 to 2000kg/minute. This
force is great enough to ram the mould satisfactorily.
• In moulding boxes, sand is filled and rammed at the same time. The density of sand which
is the result of sand’s inertia is uniform throughout the mould.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

sand slinger

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Testing: Grain fineness or Grain size test

Sieves
Sieve Shaking Machine
Collecting Pan

Motor

• The grain size is determined by grain fineness number.

• It can be tested with the help of equipment called sieve shaker.
• It consists of set of standard sieves having varying number of meshes 6,
12, 20, 30, 40, 50, 70, 100, 140, 200 and 270.
• The sieve with minimum mesh number has largest aperture and so on.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Testing: Sieve Shaking Machine

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Testing: Grain fineness or Grain size test

Sieves

Sieve Shaking Machine

Collecting Pan

Motor

The sample of sand is first washed to remove clay from it, and then it is
dried. A weighed quantity of this sand is now placed on the top sieve and the
whole unit is shaken for a definite period with the help of electric motor. The
sand falls through the apertures, and the sand of smallest size comes to the
bottom pan. The sand in each sieve is collected and weighed separately and
expressed as a percentage of the original sample weight. The percentage
retained in each sieve is multiplied by its own multiplier and all the products
are added to obtain the total product. The grain fineness number is obtained
by using the following equation

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Testing: Grain fineness or Grain size test

Sieves
Sieve Shaking Machine
Collecting Pan

Motor

Total Product M i Pi
Grain fineness number 
Total % of sand retained on sieve Pi
Where Mi = Multiplying factor of ith sieve, Pi = Percentage of sand retained in ith sieve

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Testing: Grain fineness or Grain size test

American Foundry Society (AFS) Multiplying factor

Seive series
6 3
12 5
20 10
30 20
40 30
50 40
70 50
100 70
140 100
200 145
270 200
Pan 300
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Sand Testing: Grain fineness or Grain size test

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Testing: Hardness test
• The hardness of compacted sand provides a quick indication of
mould strength and give additional insight into strength-
permeability characteristics. Hardness of moulding sand can be
measured by an instrument called hardness tester. This tester
determines the resistance of the sand to penetration by a 0.2 inch
(5.08 mm) diameter spring loaded steel ball.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Testing: Permeability Test

2000cc Bell Jar

Water

Mercury
Seal Manometer

Permeability Tester
Valve

• Permeability is measured by the quantity of air that will pass

through a standard specimen of the sand under given pressure in a
prescribed time.
• The permeability apparatus uses the standard rammed 5.08cm
diameter by 5.08cm height test piece.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Testing: Permeability Test
2000cc Bell Jar

Water

Mercury
Seal Manometer

Permeability Tester
Valve

A permeability meter, has a cylindrical water tank in which an

inverted bell or air holder, properly balanced, is floating. By
properly opening the valve, air, which is trapped under the bell, will
flow through the sand specimen as shown. Mercury around the
bottom of the specimen tube provides an airtight seal. The pressure
of this air is obtained with the water manometer and straight scale. It
should be close to 10 cm of water, which correspond to a pressure of
10 gm per sq. cm.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Sand Testing: Permeability Test

2000cc Bell Jar

Water

Mercury
Seal Manometer

Permeability Tester
Valve

• Permeability number is defined as the volume of air in cc that

will pass per minute under a pressure of 1 gm per sq. cm
through a specimen, which is 1 sq. cm in cross sectional area
and 1 cm deep.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Testing: Permeability Test

Vxh
Permeability Number 
Px axt
Where, v = Volume of air = 2000cc
• h = Height of the sand specimen = 5.08cm
• p = Air pressure = 10 gm per sq. cm.
• a = cross- sectional area of the specimen = 20.268 sq. cm.
• t= Time for 2000cc of air in Minutes

Putting these values, the formula reduces to:

501.28 50.128 3007.2

Permeability Number   
p xTime in min Time in min Time in sec

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand Testing: Strength Test

Dial
Jaws to
Indicator
hold jobs

High Low a) Compression b) Shear

Rotating
Handle
Universal Sand
Testing Machine
c) Tensile

• To find out the holding power of various bonding materials in green and dry
sand moulds, strength tests are performed. It is done on universal sand testing
machine. moulding sand can be tested for compressive, tensile strength and
shear strength.
• The specimen is held between the grips. Hand wheel when rotated, actuates
mechanism to build pressure on the specimen. Dial indicator fitted on the tester
measures the deformation occurring in the specimen. There are two
manometers, one for low strength sand and other for high strength sands.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Cores and core making
• Cores:
– Castings are often required to have holes, recesses etc. of
various sizes and shapes.
– Cores are used for making holes or cavities or recesses, which
cannot normally be produced by pattern alone.
– These cores are obtained by using core sand; cores are
separately made, in boxes known as core boxes.
• Core prints:
– For supporting the cores in the mould cavity, an impression in
the form of recesses is made in the mould with the help of a
projection suitably placed on the pattern.
– This projection on the pattern is known as the core prints.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Cores and core making
• Core Sands:
• Core sand is composed of either dry sand or synthetic sand mixed with
core oil and/ or binders.
• Generally Core oils (composed of linseed oil, resin, light mineral oil
(50 to 60% linseed oil, 25% resin and the rest is mineral oil) are used
as they are economical and produces .
• The normal binders are organic in nature, because these would be
burnt away by the heat of the molten metal and thus make the core
collapsible during the cooling of the casting.
• Binders are of following types:
• Thermo setting plastic core binders (Rosin, pitch): Gives high
strength.
• Thermo setting resin core binders (Urea, phenol): Gives high strength.
• Protein binders (Gelatine, glue): Where collapsibility is the main
criterion.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Cores and core making
• Characteristics of Core and Core Sand:
– Green strength: Core sand should be strong enough to retain the shape
till it goes for baking.
– Dry strength: It should have adequate dry strength so that when the
core is placed in the mould, It should be able to resist the metal
pressure acting on it.
– Refractoriness: Since in most cases, the core is surrounded all around
it is desirable that the core material should have higher refractoriness.
– Permeability: Some of the gases evolving from the molten metal and
generated from the mould may have to go through the core to escape
out of the mould. Hence cores are required to have higher
permeability.
– Collapsibility: As the casting cools, it shrinks, and unless the core has
good collapsibility it is likely to provide resistance to against
shrinkage and thus cause hot tears.
– Smoothness: The surface of the core should be smooth so as to
provide a good surface finish to the castings
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Cores and core making
• Core Boxes
• A core box is a type of pattern being used for making cores. It is made of wood,
brass aluminium or any suitable material. In core boxes sand is rammed or
packed to form the cores and thus impart the desired shape to them. A core box is
so constructed that it gives the exact size and shape of the core required.

A typical core box

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Cores and core making
• Types of core boxes:
• Half core box: In half core boxes, half of the core is made at one time
as shown in the figure. Another half portion of the core is made
separately and both are baked. The portions are cemented after baking
and then used as a core.
• Slab or dump core box: It is similar to a half core box in construction
but makes a full core at a time as shown in the figure. It is used for
making rectangular, square, triangular and trapezoidal cores.
• Split core box: A split core box consists of two parts. These parts can
be joined together with the help of dowels or fasteners temporarily to
show full core cavity after joining.
• Strickel core box: It consists of a strickel board made of wood and a
core box as shown in the figure. The sand is dumped in a core box and
rammed. The top surface of the core in the core box is given the
desired shape with the help of a strickel board.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Types of core boxes

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Cores and core making
• Types of Cores
– Horizontal Core
– Vertical core
– Balanced core
– Hanging Core
– Wing/Drop Core
Horizontal Core

Hanging Core

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Cores and core making

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Cores and core making
• The steps involved in core making are :
• Mixing core sand:
– The dry sand is mixed with required amount of core oil and binders.
The mixer must be homogeneous so that core will be of uniform
strength through out. The mixing of sand is performed in paddle
mixers or mullers.
• Ramming of the core sand:
– Cores are usually made in core boxes. The core box is filled with core
sand, rammed and struck off.
• Venting of the core:
– Vent holes are provided in cores in order to allow the escape of gases.
These vents are usually made with wires or rods.
• Reinforcing the core:
– Some cores require internal reinforcements to prevent from breakage
or shifting, when metal is poured in the mould. Wires placed within
the sand serve this purpose.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Cores and core making
• Baking of the core:
– The cores after removing from the core boxes are baked at temperature upto
about 2600C to develop the strength obtainable from the binders in the core
sand. The baking is done in oven, dielectric bakers etc.
• Cleaning of the core:
– The cleaning of cores consists of trimming, brushing, coating and muddling.
• Trimming: It is done to remove fins arising from loose joints or loose
pieces in the core boxes.
• Brushing: It is done to remove loose sand.
• Coating: The core is coated with high refractory materials to increase its
refractoriness.
• Muddling: It is localized coating to make the core smooth. In this step,
cavities in the core surface are filled.
• Sizing of the core:
– The cores are then brought to required size by removing excess material.
• Joining of the core:
– Sometimes cores are made of two or more pieces, so before they can be used
they are joined by pasting or bolting.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Core making Example

Figure 1: Core boxes for pump housing core.

Figure 2: Ramming up the core.

Figure 3: Placing the reinforcing rods.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Core making Example

Figure 4: Cutting vents. Figure 5: Drag core turned out.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Core making Example

Figure 7: Applying core paste.

Figure 6: Cope core turned out. Figure 8: Assembling the two core halves.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Core print design
• Major considerations in core print design are listed below.
1. The print must balance the body, so that the core stays in place during mould
assembly.
2. The print must withstand the buoyancy force of the metal and not get crushed.
3. The print must not shift during mould filling.
4. The print should minimize the deflection of the core.
5. The print should maximize the heat transfer from the core to the mould.
6. The print should allow the internal gases generated in the core to escape to the
mould.
7. Unsymmetrical holes should have foolproof prints to prevent incorrect assembly.
8. The prints of adjacent cores may be combined into one.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Core print design
• Let us analyze the forces on a horizontal simply supported core. Consider a
cylindrical core of diameter d, body length l, print length a and print diameter D.
Let ρmetal and ρcore be the densities of the molten metal and core material,
respectively. Also, let σcomp be the compressive strength of the mould material.
• Self weight of core body WB = π d2 l ρcore / 4
• Self weight of core prints WP = π D2 a ρcore / 4
• Total weight of core W = WB + WP
• Applying the first design rule to balance the core during placement in mould, we
have WB ≤ WP
• The buoyancy force B on the core, B = π d2 l ρmetal / 4
• The net force on the core (upward) = B – W
• The compressive stress on each core print σprint = 0.5 (B - W) / (aD)
• Applying the second rule to prevent core failure by crushing due to buoyancy
forces, σprint ≤ σcomp
• For vertical cores, there are two additional considerations. One is that the buoyancy forces
transmitted by the core print may shear the top part of the mould. This is prevented by ensuring
sufficient thickness of the mould wall above the core print. The second consideration is that the core
print must be tapered to facilitate its placement in mould. The draft angle ranges from 2-4 degrees.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Core print calculations
• The main force acting on the core when metal is poured in the mould cavity is
due to buoyancy force. Hence to fully support the buoyancy force, it is necessary
that the following condition (empirical) is satisfied, p 350 A; where A is the
core print area in mm2.
• If the above equation is not satisfied, then it would be necessary to provide
additional support by the way of chaplets.
• In order to calculate the chaplet area, we need to know the unsupported load:
• Unsupported load = p - 350 A
• If the Unsupported load is greater than zero then the chaplet are required is
29mm2 for every Newton of unsupported load.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Cores and core making
• Chaplets
– Chaplets are metal supports used to hold a core in place when core prints are
inadequate. It is absolutely necessary that they be clean. Rust, oil, grease,
moisture, or even finger marks, cause poor fusion or porosity. Chaplets
should be the same composition as the casting, if possible. The strength of the
chaplet must be enough to carry the weight of the core until sufficient metal
has solidified to provide the required strength, but it should be no heavier
than necessary.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Cores and core making
• Types of chaplets

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples ( Green sand mould preparation)
• Firstly, one half of the pattern is placed with its flat surface on a mould board,
and the drag section of the flask is set over the pattern on the same board.
• After powdering the pattern with lycopodium, talc, or graphite, a layer of facing
sand is then riddled over the pattern.
• The drag is then filled with layers of green sand mixture. The sand is then
compacted with rammer.
• After the sand is rammed, a strickle is used to scrape off the excess sand level
with the top of the flask.
• The mould is then vented by sticking it with a fine stiff wire at numerous places.
• A small amount of loose sand is sprinkled over the mould, and bottom board is
placed on the top.
• The drag is then rolled over, the moulding board is then removed, and the upper
surface is sprinkled with parting sand.

Drag
Step 1

Pattern
Moulding
Board

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples ( Green sand mould preparation)
• The remaining half of the pattern and the cope section of the flask are
then assembled.
• Tapered wooden pegs to serve as sprue and riser are placed in proper
position on the pattern, which is riddled over with facing sand, and then
the cope is filled with green sand.
• The operations of filling, ramming, venting of the cope proceed in the
same manner as in the drag.

Riser Pin

Sprue Pin

Step 2

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples ( Green sand mould preparation)
• Now, the wooden pegs are removed from the cope and a funnel shaped
opening is scooped out at the top of the sprue to form the pouring basin.
• Next the cope is lifted off and placed on a board with parting line upward.
• An iron bar is now pushed down to the pattern and rapped sideways so as to
loosen the pattern in the mould.
• Next the pattern is drawn out.

Weight

Vents
Cope
Riser

Sprue
Core Step 3

Runner
Drag

Gate

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples ( Green sand mould preparation)
• The runner and the gate are cut in the drag from the pattern to the sprue. Now
the core must be placed in the print left by the pattern.
• Mould surfaces are then cleaned.
• Finally the mould is assembled, the cope being carefully placed on the drag
so that the flask pins fit into the bushes.
• Before pouring the molten metal, the cope is sufficiently loaded to prevent it
from floating up when metal is poured.
• The mould is now ready for casting.

Weight

Pouring basin
Vents
Cope Riser

Sprue
Core Step 3

Runner
Drag

Gate

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (a cast iron steel elbow )

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure: Pattern set in drag with gating system parts

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure: Hand packing riddled sand around the pattern

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure Ramming a deep pocket.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure: Striking off the drag

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure: Drag flipped over and ready for the cope

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure: . Cope with pattern and gating pieces set

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure: Ramming the partially filled cope.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure: Venting the cope

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure: Cope removed and Start of the

pattern draw.

Figure: Pattern completely drawn.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure: Setting the core.

Figure: Cope and drag ready for closing.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)
Figure: Clamped mold with weights and
pouring basin.

Figure: Pouring the mold.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (pump housing)

Figure: Finished pump housing casting.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (propeller)

Figure: Propeller set in the drag..

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Sand casting examples (propeller)
Figure: Propeller in the drag with parting
line cut.

Figure: Drawn cope.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Sand casting examples (propeller)
Figure: Mold ready for closing.

Figure: As-cast propeller.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Important points to be considered for GATING SYSTEMS Design
• The mould should be completely filled in the smallest time possible without
having to raise metal temperatures nor use higher metal heads.
• The metal should flow smoothly into the mould without any turbulence. A
turbulent metal flow tend to form dross in the mould.
• Unwanted material such as slag, dross and other mould material should not be
allowed to enter the mould cavity.
• The metal entry into the mould cavity should be properly controlled in such a
way that aspiration of the atmospheric air is prevented.
• A proper thermal gradient be maintained so that the casting is cooled without any
shrinkage cavities or distortions.
• Metal flow should be maintained in such a way that no gating or mould erosion
takes place.
• The gating system should ensure that enough molten metal reaches the mould
cavity.
• The gating system design should be economical and easy to implement and
remove after casting solidification.
• Ultimately, the casting yield should be maximised.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS

Figure: A typical gating system

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
ELEMENTS OF GATING SYSTEMS

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS

Figure: Pouring basin

Figure: Sprue
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
ELEMENTS OF GATING SYSTEMS

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS
• Pouring Basin: It is the funnel-shaped opening, made at the top of the mold. The
main purpose of the pouring basin is to direct the flow of molten metal from ladle
to the sprue. It should be made substantially large and is kept near the edge of the
mold box. Pouring basin must be deep enough to reduce the vortex formation and
is kept full during entire pouring operation.
• Sprue: It is a passage which connects the pouring basin to the runner or ingate. It
is generally made tapered downward to avoid aspiration of air. The cross section
of the sprue may be square, rectangular, or circular. The round sprue has a
minimal surface area exposed to cooling and offers the lowest resistance to the
flow of metal. The square or rectangular sprue minimizes the air aspiration and
turbulence.
• Sprue well: It is located at the base of the sprue. It arrests the free fall of molten
metal through the sprue and turns it by a right angle towards the runner.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS
• Cross-gate or Runner: In case of large casting, the fluidity length of the molten
metal is less than the maximum distance required to be travelled by the molten
metal along the flow path. So it is necessary to provide the multiple ingates to
reduce the maximum flow distance needed to be travelled by the molten metal.
Moreover, in a multi-cavity mould also each cavity must have at least one ingate,
therefore it is necessary to connect all the ingate to a common passageway which
is finally linked with the sprue to complete the flow path. This passage way is
called runner. The cross section of the runner is usually rectangular to get a
streamlined flow with less turbulence. The runner must fill completely before
letting the molten metal enter the ingates. In castings where more than one ingate
is present, the cross sectional area must be reduced after each ingate (by an
amount equal to area of that ingate), to ensure the uniform flow through the
ingates.
• Ingate or Gate: It is a small passage which connects the runner to the mould
cavity. The cross section is square, rectangular and trapezoidal.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Gating Ratio
• There is a definite relationship between the cross-sectional areas of the sprue,
runners, and in-gates, to produce the best filling conditions for the mold. The rate
of filling the mold should not exceed the ability of the sprue to keep the entire
gating system full of liquid metal at all times. The cross section of the runner
should be reduced in size as each gate is passed. This keeps the runner full
throughout its entire length and promotes uniform flow through all of the gates. If
this procedure is not followed in a multiple-ingate system, all of the metal will
have a tendency to flow through the ingates farthest from the sprue.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS
• Types of Gating Systems The gating systems are of two types:
– Pressurized gating system
– Un-pressurized gating system
• Pressurized Gating System (Typical gating ratio 1:2:1)
• The total cross sectional area decreases towards the mold cavity
• Back pressure is maintained by the restrictions in the metal flow
• Flow of liquid (volume) is almost equal from all gates
• Back pressure helps in reducing the aspiration as the sprue always runs full
• Because of the restrictions the metal flows at high velocity leading to more
turbulence and chances of mold erosion
• In this system pressure is maintained at the ingates by the fluid. In order to
achieve this total gate area should be less than the sprue exit area. In other words
choke is located at the ingate. This system keeps gating channels full of metal.
Due to pressurization the flow separation is absent in the system also air
aspiration is minimized. The filling rate and yield increase. However, high metal
velocity will cause turbulence.
• Because of the turbulence and the associated dross formation, this type of
gating system is not used for light alloys but can be advantageous for ferrous
casting.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
ELEMENTS OF GATING SYSTEMS

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS
• Un-Pressurized Gating System
• The total cross sectional area increases towards the mold cavity
• Restriction only at the bottom of sprue
• Flow of liquid (volume) is different from all gates
• aspiration in the gating system as the system never runs full
• Less turbulence
• In this system choke is located at the sprue exit. Hence the sprue exit area is less
than the total gate area, for example 1:2:2, 1:4:4. Due to lower velocity, filling
rate will be less. The process yield increases but it suffers from the disadvantage
of flow separation.
• This is particularly useful for casting drossy alloys such as aluminum and
magnesium alloys.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Runner
• The gating system should be designed in such a way that runner should run full.
When the amount of molten metal coming down the sprue is more than the
amount flowing through the ingates, the runner would be full and thus slag
trapping would take place.

Figure: Runner

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS
• Gating System and Types: Depending upon the orientation of the parting plane,
the gating system can be classified as horizontal and vertical gating systems
• In horizontal gating systems, parting plane is horizontal and contains runners and
ingates. The sprue is vertical, perpendicular to the parting plane. These are
suitable for flat castings filled under gravity, such as in green sand casting and
gravity die casting.
• In the vertical gating system, parting plane is vertical and contains runners and
ingates. For gravity filling processes (high pressure sand molding, shell molding
and gravity die casting) the sprue is vertical and for pressure die casting sprue is
along the parting plane. It is suitable for tall castings.

Source: M.Tech Dissertation, Dolar Vaghasia, IIT, Bombay, 2009

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
ELEMENTS OF GATING SYSTEMS
• Gating System and Types: Depending upon the orientation of the parting plane,
the gating system can be classified as horizontal and vertical gating systems
• In horizontal gating systems, parting plane is horizontal and contains runners and
ingates. The sprue is vertical, perpendicular to the parting plane. These are
suitable for flat castings filled under gravity, such as in green sand casting and
gravity die casting.
• In the vertical gating system, parting plane is vertical and contains runners and
ingates. For gravity filling processes (high pressure sand molding, shell molding
and gravity die casting) the sprue is vertical and for pressure die casting sprue is
along the parting plane. It is suitable for tall castings.

Source: M.Tech Dissertation, Dolar Vaghasia, IIT, Bombay, 2009

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
ELEMENTS OF GATING SYSTEMS
• TYPES OF GATES: There are three general classifications for gates which are
commonly used. They are: (1) bottom gates, (2) top gates, and (3) parting gates (4)
Step gates.
• Top Gates. Top gating of a casting is limited by the ability of the mould to withstand
erosion, because the molten metal is usually poured through an open-top riser.
Contrary to the characteristics of bottom gating, top gating has the advantage of
producing favorable temperature gradients, but the disadvantage of excessive mould
erosion. This method of gating is usually used for castings of simple design which are
poured in gray iron. Top gating is not used with nonferrous alloys which form large
amounts of dross when agitated.

Figure: Top gate

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
ELEMENTS OF GATING SYSTEMS
• Bottom Gates. Bottom gates are most generally used because they keep mould
and core erosion to a minimum. In spite of this, they have the very decided
disadvantage of causing unfavorable temperature gradients in the casting, which
make proper feeding particularly difficult and often impossible. When using
bottom gates, as the metal rises in the mould, it heats the mould with which it
comes in contact. This produces relatively cold metal in the riser with
considerably hotter metal next to the gate. In other words, there is hot metal and
hot mould near the gate and cold metal in a cold mould near the riser. Such
conditions are opposite to those desired for directional solidification in a casting.
The risers should contain the hottest metal in the hottest part of the mould, and
the coldest mould parts should be at points farthest removed from the risers.

Figure: Bottom gate

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
ELEMENTS OF GATING SYSTEMS
• Parting Gates. Parting-line gates are used most frequently because they are the
easiest for the moulder to construct, particularly in jobbing work. In addition, it is
usually possible to gate directly into a riser. The main disadvantage of parting
gates is that the molten metal drops in the mould to fill the drag part of the
casting. Such a drop often causes erosion or washing of the mould. In nonferrous
metals, dross formation is aggravated and air is often trapped to produce inferior
castings.
• Step Gating. The theory behind the step gate is that as the metal rises in the
mould, each gate will feed the casting in succession. This would then put the hot
metal in the riser where it is desired.

Figure: Step gate

Figure: Parting gate
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
ELEMENTS OF GATING SYSTEMS
• Ingate Design:
• The following points should be kept in mind while choosing the positioning of
the ingates:
– In-gate should not be located near a protruding part of the mould to avoid the
striking of vertical mould walls by the molten metal stream.
– In-gates should preferably be placed along the longitudinal axis of the mould
wall.
– In-gates should not be placed near a core print or a chill.
– In-gate cross sectional area should preferably be smaller than the smallest
thickness of the casting so that the in-gates solidify first and isolate the
castings from the gating system. This would reduce the possibility of air
aspiration through the gating system in cases of metal shrinkage.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

ELEMENTS OF GATING SYSTEMS

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Gating nomenclature

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

GENERAL RULES OF GATING
• The following general rules are given as a guide in making good gating systems:
• 1. Use Round Sprues. (a) Round gates or the closest approach to round gates are
preferred. (b) A circular cross section has the minimum surface exposed for
cooling and offers the lowest resistance to flow.
• 2. Taper the Sprue. The sprue should be tapered with the smaller end toward the
casting. This makes is possible to keep the down-gate full of metal when pouring.
Never locate a tapered sprue so that metal is poured into the smaller end.
• 3. Streamline the Gating System. Gating systems having sudden changes in
direction cause slower filling of the mold cavity, are easily eroded, and cause
turbulence in the liquid metal with resulting gas pickup. Streamlining of the
gating system eliminates or minimizes these problems. Avoid right-angle turns.
• 4. Use Patterns for the Gates. The gating system should be formed as part of the
pattern whenever possible. The use of patterns for the gates permits the sand to
be rammed harder and reduces sand erosion or washing. Hand-cut gates expose
loosened sand which is easily eroded by the flowing metal.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Maintain Proper Gating Ratio Example
• An example of the use of gating ratio can be made with figure. Aluminum was
used to make this flat plate casting, and one of the gating ratios that has proven
successful for this type of casting is a 1:3:3 ratio. The first number refers to the
cross-sectional area of the sprue base, the second number refers to the total cross
section of all the runners from that sprue, and the third number refers to the total
cross-sectional area of the ingates. In other words, the area of the sprue base is
1/3 that of the total area of the runners, and the total cross-sectional area of the
runners equals the total cross-sectional area of the ingates.
• The size of the ingate for this plate casting was selected to be 1/4 inch thick and
1-1/2 inches wide. The individual ingate then has an area of 3/8 square inch.
There are four ingates, so the total ingate area is 4 x 3/8 square inch, or 1.5 square
inches. The total runner area is then also 1.5 square inches, as determined by the
gating ratio. Since there are two runners, each runner must have a cross-sectional
area of 0.75 square inches. In figure, this is shown by the runner dimensions of
3/4 inch thick by 1 inch wide. To complete the gating system, the sprue base
must have a cross-sectional area equal to 1/3 that of the runners. This is equal to
1/2 square inch. A sprue with a base diameter of 4/5 inch will satisfy this
requirement.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

GENERAL RULES OF GATING
6. Maintain Small Ingate Contact. The area of contact between the ingate and
the casting should be kept as small as possible.
7. Utilize Natural Channels. Ingates should be located so that the incoming flow
of metal takes place along natural channels in the mold and does not strike
directly on mold surfaces or cores. The continuous flow of metal against a mold
or core surface quickly burns out the binder and washes the loose sand into the
casting.
8. Use Multiple Ingates. Unless a casting is small and of simple design, several
ingates should be used to distribute the metal to the mold, fill it more rapidly,
and reduce the danger of hot spots.
9. Avoid Excessive Ingate Choke. The in-gate should not be choked at the mold
so that it causes the metal to enter the mold at such a high speed that a shower
effect is produced. Besides excessive turbulence and oxidation of the metal, the
mold may not be able to withstand this eroding force. Choking of the ingate to
assist in gate removal is a proper procedure if a number of ingates are used to
allow an adequate amount of metal to enter the mold without jet action.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

GENERAL RULES OF GATING
10. In-gate should not be located near a protruding part of the mould to avoid the
striking of vertical mould walls by the molten metal stream.
11. In-gates should preferably be placed along the longitudinal axis of the mould
wall.
12. In-gates should not be placed near a core print or a chill.
13. In-gate cross sectional area should preferably be smaller than the smallest
thickness of the casting so that the in-gates solidify first and isolate the castings
from the gating system. This would reduce the possibility of air aspiration
through the gating system in cases of metal shrinkage.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISERS
• The principal reason for using risers is to furnish liquid metal to compensate for
solidification shrinkage in the casting. In addition to this main function, a riser
has other reasons for its use. It eliminates the hydraulic-ram effect (similar to
water "pound" when a valve is closed suddenly), shown when the mould is full,
flows off cold metal, and vents the mould.
• Just at the time that a mould is completely filled with metal, there can be a
sudden and large increase in pressure in the mould because of the motion of the
flowing metal. This added pressure may be enough to cause a run-out of the
casting or may produce a deformed casting. A riser permits the metal to flow
continuously into it instead of coming to a sudden stop. This reduces the pressure
or hydraulic-ram effect which produces these defects. An open riser permits the
man pouring the mould to see how rapidly the mould is filling and provides him
with a means to regulate the flow of metal.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISERS
• GENERAL RULES OF RISERING
• The most important function of a riser is that of a reservoir of heat and molten
metal. To be effective, it must be the last portion of the casting to
solidify. There are four primary requirements which a satisfactory riser should
meet:
1. The volume of the riser should be large enough to compensate for the metal
contraction within the area of the casting it is designed to feed.\
2. Enough fluid metal must be in the riser to penetrate to the last cavity within its
feeding area.
3. The contact area of the riser with the casting must fully cover the area to be
fed, or be designed so that all the needed feed metal in the riser will pass into
the casting.
4. The riser should be effective in establishing a pronounced temperature gradient
within the casting, so that the casting will solidify directionally toward the
riser.
Accordingly, the shape, size, and location of the riser must be effectively
controlled.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

TYPES OF RISERS
• There are two general types of risers, the open riser and the blind riser. The open
riser is open to the air while the blind riser is not cut through to the surface of the
mold. A blind riser cannot be seen when the mold is closed.
• Open Risers. Open risers are used widely because they are simple to mold. Their
greatest use is in large flat castings which have numerous heavy sections.
• Blind Risers. Blind risers are advantageous because:
• 1. They facilitate bottom gating into castings by feeding the hot spot at the point
of entry of metal. Gating into the riser also preheats the riser cavity and promotes
greater feeding efficiency as well as proper temperature gradients within the
casting.
• 2. They can be located at any position in a mold to feed otherwise inaccessible
sections.
• 3. They are more efficient than open risers because they can be designed to
closely approach the ideal spherical shape, thus substantially reducing the amount
of riser metal required for satisfactory feeding. In addition, they are completely
surrounded by sand, which eliminates the chilling by radiation to the air and
keeps the metal liquid longer.
• 4. They are easier to remove from castings than open risers because they can be
more strategically positioned.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
RISERS
• Riser Shape. The rate of solidification of a metal varies directly with the ratio of
surface area to volume. In other words, for a given weight of metal, the shape
which has the smallest surface area will take the longest time to solidify. The
ratio of surface area to volume is obtained by dividing the surface area by the
volume.
• Riser Size. Practical foundry experience has shown that the most effective height
of a riser is 1-1/2 times its diameter in order to produce maximum feeding for the
minimum amount of metal used. Any riser higher than this is wasteful of metal
and may be actually harmful to casting soundness.
• Riser Location. Heavy sections of a casting have a large amount of solidification
shrinkage which must be compensated for from an outside source. Heavy
sections, therefore, are the locations for risers. An important point to remember in
the risering of a casting is that the hottest metal must be in the riser if it is to be
effective.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN
• MODULUS METHOD
• Another method for finding the optimum riser size is the 'modulus method‘,
extensively documented by Wlodawer. It has been empirically established that if
the modulus of the riser exceeds the modulus of the casting by a factor of 1.2, the
feeding during solidification would be satisfactory.
• NAVAL RESEARCH LABORATORY METHOD
• This method which is essentially a simplification of the Caine's method, defines a
shape factor to replace the freezing ratio. The shape factor is defined as

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN
• The function of a riser is to supply addition molten metal to a casting to ensure a
shrinkage porosity free casting. Shrinkage porosity occurs because of the increase
in density from the liquid to solid state of metals. To be effective a riser must
solidify after the casting and contain sufficient metal to feed the casting or
portion of a casting. Casting solidification time can be predicted using
Chvorinov’s Rule.

• Where tTS is the total solidification time of the part or riser, C is a mold constant,
V is the volume of metal, and Asurf is the total surface area of the part or riser.
• Chvorinov’s Rule provides guidance on why risers are typically cylindrical. The
longest solidification time for a given volume is the one where the shape of the
part has the minimum surface area. From a practical standpoint, the cylinder has
the least surface area for its volume and is easiest to make. Since the riser should
solidify after the casting, we want it’s solidification time to be longer than the
casting. If we want the riser to take 20% longer than the riser then we can write
the following expression:

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN
• The term V/Asurf occurs so frequently it is given a special name. It is called the
casting modulus. By using the variable M to represent the casting modulus and
simplifying, the above equation can be reduced to.

• This expression is used for the simplest method for designing a riser. It is called
the modulus method. While modern computer methods make it easier to optimize
the riser, an initial guess of the correct geometry is needed. The modulus method
provides the best method for obtaining that initial guess. The modulus for a
cylindrical riser is given be the following equation.

• Where D is the riser diameter, and H is the riser height. Determining the final
riser dimensions will require an assumption about the relationship between the
riser height and diameter. Typically riser height is twice the diameter (H=2D).
• To ensure a riser can feed a casting or casting section, it’s maximum feeding
volume should be checked against the casting or section volume. Equation
provides this check for a riser without an insulating sleeve.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN
• Where Vmax is the maximum casting volume that can be fed, Vriser is the
volume of the riser, and S is the specific shrinkage of the alloy in percent. The
specific shrinkage for a specific allow is listed in Table 1.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN EXAMPLE
• A single shifter lever part will be placed in a mold. Determine the required riser
for the shifter lever if it has a volume of 0.955 in3 and a surface area of 6.905 in2.
• It is best to produce this part with a single in-gate at the large boss on the part. To
create directional solidification and prevent shrinkage, the riser should directly
feed the cylindrical feature by being place at the in-gate.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN EXAMPLE

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN EXAMPLE
• A cylindrical riser must be designed for a sand-casting mold. The casting
itself is a steel rectangular plate with dimensions 7.5 cm x 12.5 cm x 2.0 cm.
Previous observations have indicated that the total solidification time (TST)
for this casting = 1.6 min. The cylinder for the riser will have a diameter-to-
height ratio = 1.0. Determine the dimensions of the riser so that its TST = 2.0
min.
• Solution: First determine the V/A ratio for the plate.
• Its volume V = 7.5 x 12.5 x 2.0 =187.5 cm3
• and its surface area A =2(7.5 x 12.5 + 7.5 x 2.0 + 12.5 x 2.0) =267.5 cm2
• Given that TST = 1.6 min, we can determine the mold constant Cm using a value
of n = 2 in the equation.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN EXAMPLE (Contd….)

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN EXAMPLE
• In the casting of steel under certain mold conditions, the mold constant in
Chvorinov's Rule is known to be 4.0 min/cm2, based on previous experience. The
casting is a flat plate (fig. 1) whose length l= 30 cm, width w= 10 cm, and
thickness h= 20 mm. Determine how long it will take for the casting to solidify.

• Solution:
• Area A = 2(30 x 10) + 2(30 x 2) + 2(10 x 2) = 760 cm 2
• Volume V = 30 x 10 x 2 = 600 cm3
• Chvorinov’s Rule: T TS = Cm (V/A)2 = 4(600/760)2 = 2.49 min solidify.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
RISER DESIGN EXAMPLE
• A cylindrical-shaped part (fig. 2) is to be cast out of aluminum. The radius of
the cylinder r= 250 mm and its thickness h= 20 mm. If the mold constant Cm =
2.0 sec/mm 2 in Chvorinov's Rule, how long will it take the casting to solidify?

• Solution:
• Area A = 2 π r 2+ 2π r h = 2 π (250)2 + 2π (250) (20) = 424,115 mm2
• Volume V = π r2 h = π (250)2(20) = 3,926,991 mm3
• Chvorinov’s Rule: TTS = Cm(V/A)2 = 2 (3,926,991 / 424,115)2
• = 171.5 s = 2.86 min
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
RISER DESIGN EXAMPLE
• In casting experiments performed using a certain alloy and type of sand mold, it
took 155 sec for a cube-shaped casting to solidify. The cube was 50 mm on a
side.
• (a) Determine the value Cm of the mold constant in Chvorinov's Rule.
• (b) If the same alloy and mold type were used, find the total solidification time
TTS for a cylindrical casting in which the diameter r = 15 mm and length h = 50
mm.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN EXAMPLE
• Solution:
• (a) Area A = 6 x (50)2 = 15,000 mm2
• Volume V = (50)3 = 125,000 mm3
• (V/A) = 125,000 / 15,000 = 8.333 mm
• Cm = T TS/ (V/A)2= 155 / (8.333)2
• = 2.232 s/mm2

• (b) Cylindrical casting with r = 15 mm and h = 50 mm.

• Area A = 2πr 2 + 2πrh = 2π (15) 2 + 2π(15)(50) = 6126 mm2
• Volume V = πr2h = π(15)2 (50) = 35,343 mm 3
• V/A = 35,343 / 6126 = 5.77
• TTS = 2.232 (5.77)2 = 74.3 s = 1.24 min.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

RISER DESIGN

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

SOLIDIFICATION TIME
• Whether the casting is pure metal or alloy, solidification takes time. The total
solidification time is the time required for the casting to solidify after pouring. This time is
dependent on the size and shape of the casting by an empirical relationship known as
Chvorinov’s rule, which states:

• Where TTS= total solidification time, min; V= volume of the casting, cm3 (in3); A=surface
area of the casting, cm2 (in2); n is an exponent usually taken to have a value = 2; and Cm
is the mould constant. Given that n = 2, the units of Cm are min/cm2 (min/in2), and its
value depends on the particular conditions of the casting operation, including mould
material, thermal properties of the cast metal, and pouring temperature relative to the
melting point of the metal. The value of Cm for a given casting operation can be based on
experimental data from previous operations carried out using the same mould material,
metal, and pouring temperature, even though the shape of the part may be quite different.
Chvorinov’s rule indicates that a casting with a higher volume-to-surface area ratio will
cool and solidify more slowly than one with a lower ratio. This principle is put to good use
in designing the riser in a mould. To perform its function of feeding molten metal to the
main cavity, the metal in the riser must remain in the liquid phase longer than the casting.
In other words, the TTS for the riser must exceed the TTS for the main casting. Since the
mould conditions for both riser and casting are the same, their mould constants will be
equal. By designing the riser to have a larger volume-to-area ratio, we can be fairly sure
that the main casting solidifies first and that the effects of shrinkage are minimized.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Solidification Time : Sand Casting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

DIRECTIONAL SOLIDIFICATION
• In order to minimize the damaging effects of shrinkage, it is desirable for the regions of
the casting most distant from the liquid metal supply to freeze first and for solidification
to progress from these remote regions toward the riser(s). In this way, molten metal will
continually be available from the risers to prevent shrinkage voids during freezing. The
term directional solidification is used to describe this aspect of the freezing process and
the methods by which it is controlled. The desired directional solidification is achieved by
observing Chvorinov’s rule in the design of the casting itself, its orientation within the
mould, and the design of the riser system that feeds it. For example, by locating sections
of the casting with lower V/A ratios away from the riser, freezing will occur first in these
regions and the supply of liquid metal for the rest of the casting will remain open until
these bulkier sections solidify.
• Another way to encourage directional solidification is to use chills—internal or external
heat sinks that cause rapid freezing in certain regions of the casting. Internal chills are
small metal parts placed inside the cavity before pouring so that the molten metal will
solidify first around these parts. The internal chill should have a chemical composition
similar to the metal being poured, most readily achieved by making the chill out of the
same metal as the casting itself. External chills are metal inserts in the walls of the mould
cavity that can remove heat from the molten metal more rapidly than the surrounding sand
in order to promote solidification. They are often used effectively in sections of the casting
that are difficult to feed with liquid metal, thus encouraging rapid freezing in these
sections while the connection to liquid metal is still open.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

DIRECTIONAL SOLIDIFICATION
• As important as it is to initiate freezing in the appropriate regions of the cavity, it is also
important to avoid premature solidification in sections of the mould nearest the riser. Of
particular concern is the passageway between the riser and the main cavity. This
connection must be designed in such a way that it does not freeze before the casting,
which would isolate the casting from the molten metal in the riser. Although it is generally
desirable to minimize the volume in the connection (to reduce wasted metal), the cross-
sectional area must be sufficient to delay the onset of freezing. This goal is usually aided
by making the passageway short in length, so that it absorbs heat from the molten metal in
the riser and the casting.

FIGURE: (a) External chill to encourage rapid freezing of the molten metal in a thin section
of the casting; and (b) the likely result if the external chill were not used.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Expendable mould with multiple use pattern (Shell Molding)
• First a pattern is made of metal. The iron pattern is heated to +/-200°C.
• The pattern is attached to a dump box and sprayed with a releasing agent;
similar to putting oil in a baking pan.
• The dump box contains fine sand mixed with thermo setting resin binder.
• The dump box is rotated with the pattern now at the bottom and the sand
that was once at the bottom is now on top.
• The sand mixture falls against the pattern and gets heated in this manner,
the resin cures, causing the sand grains to adhere to each other forming
sturdy shell that exactly conforms to the dimensions and shape of the
pattern and constitutes half of a mould.
• After a 5mm thick shell is formed, due to melting and solidifying of the
thermosetting binder, the dump box is rotated and the unused sand falls to
the bottom.
• The pattern and shell are then put in an oven at 350°C –400oC to cure the
resin.
• The pattern is removed by the ejector pins.
• Typically, two pattern shells are used together. A backing material like
sand or steel shot is used and the metal is poured into the mould.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting defects
• Several types of defects may occur during casting, considerably reducing the total
output of castings besides increasing the cost of their production.
• It is therefore essential to understand the causes behind these defects so that they may
be suitably eliminated.
• Casting defects may be defined as those characteristics that create a imperfection or
deficiency contrary to the quality specifications imposed by the design and service
requirements.
• Defects in castings do not just happen. They are caused by faulty procedure (1) in one
or more of the operations involved in the casting process, (2) in the equipment used,
or (3) by the design of the part. A casting defect is often caused by a combination of
factors which makes rapid interpretation and correction of the defect difficult
• The most common casting defects can be classified into the following categories:
– Gas defects
– Shrinkage cavities
– moulding material defects
– Pouring metal defects
– Metallurgical defects
– mould preparation defects.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (Gas defects)
• Blow holes and open blows:
– These are the spherical, flattened or elongated cavities present inside
the casting or on the surface. A blow or blowhole is a smooth cavity
caused by gas in the molten metal.
– On the surface they are called open blows and inside, they are called
blow holes.
– It is an excessively smooth depression on the outer surface of a
casting. Blow holes are entrapped bubbles of gases with smooth walls.
– Causes:
• High moisture content in the moulding sand.
• Low permeability of moulding sand.
• Hard ramming of the sand.
• Improper venting.
– Remedies:
• This defect can be eliminated by ensuring proper venting and
using proper moulding sand.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting defects: Blow
Figure. Blow. (Caused by high
moisture content)

Figure. Blow and expansion scab. (Caused

by hard ramming of the sand)

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (Gas defects)
• Air inclusions or Gas Holes or Internal air pocket
– The atmospheric and other gases absorbed by the molten metal in
the furnace, in the ladle, and during the flow in the mould, when
not allowed to escape, would be trapped inside the casting and
weaken it.
– This appears as small holes inside the casting and is caused by
rapid pouring of the molten metal.
– Causes:
• Higher pouring temperature which increases the amount of gas
absorbed.
• Poor gating system
• Excessively moist sand.
– Remedies:
• This defect can be eliminated by ensuring proper pouring
temperature, and by degasifying the molten metal.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting defects (Gas defects)
• Pin hole porosity:
– A pinhole is a type of blow that is unusual because of its small
size. These are numerous holes of small diameter, usually less
than 2mm, visible on the outer surface of the casting.
– These are caused by the absorption of hydrogen or carbon
monoxide when the moisture content of the sand is high.
– Causes:
• High moisture content in the moulding sand.
• Low permeability of moulding sand.
• Improper melting and fluxing practices.
• Hydrogen can get entrapped by disassociation of moisture in
the moulding sand
– Remedies:
• This defect can be eliminated by using proper moulding sand
and using proper melting and fluxing practice.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting defects: Pin holes

Figure. Pin holes. (Caused by high moisture content of the sand)

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (Shrinkage cavities)
• Shrinkage cavities:
– These are caused by the liquid shrinkage occurring during the solidification of
the casting. It is void or depression in the casting caused mainly by
uncontrolled and haphazard solidification of metal. A shrink or shrinkage
cavity is a rough cavity caused by contraction of the molten metal. It is quite
often impossible to tell whether a particular hole in a casting is a shrink or a
blow. Gas will aggravate a shrink defect, and shrinkage will aggravate a gas
defect. The distinction can usually be made that gas pressure gives a cavity
with smooth sides (blow) and contraction or lack of feeding gives a cavity
with rough sides (shrink).
– To compensate this, proper feeding of liquid metal is required as also proper
casting design.
– Causes:
• Incorrect metal composition.
• Incorrect pouring temperature.
• Improper location and size of gates and runner and riser.
– Remedies: This defect can be eliminated by ensuring proper mould design,
so that solidification rate is uniform. Achieving directional solidification
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting defects: Shrinkage cavities

Figure. Surface shrink. (Caused by

improper feeding)

Figure. Gross shrink. (Caused by inadequate

feeding)

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (moulding material defects)
• Rat tail, buckle, and scab :
– A rat tail, buckle, and scab all originate in the same way and differ mainly in
degree. They are caused by uncontrolled expansion of the sand. If the condition
is not too bad, a rat tail is formed. The surface of the sand buckles up in an
irregular line that makes the casting look as though a rat has dragged his tail
over it. If sand expansion is even greater, the defect is called a buckle. If it is
still worse so that molten metal can get behind the buckled sand, it is a scab.
– Scabs are sort of projection on the casting which occur when a portion of the
mold face or core lifts and the metal flows beneath in thin layer.
– During casting when sand face of the mold gets heated up and expands,
sometimes there occurs a crack.
– Molten metal enters the crack and flows behind the layer of sand, and causes
scabs.
– Causes:
• Using molding sand without cushion materials
• Using molding sand having high coefficient of thermal expansion
• Using very fine sand having low permeability and moisture content.
– Remedies: This defect can be eliminated by mixing additives such as wood
flour, sea coal.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects: Rat tail and scab

Figure A & B. Rattails. (Sand lacked good expansion properties)

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects : Cut or wash
• A cut or wash is erosion of the sand by the stream of molten metal.
It often shows up as a pattern around the gates and usually causes
dirt in some part of the casting.
• This may be caused by the molding sand not having enough
strength or the molten metal flowing at high velocity.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (moulding material defects)
• Metal penetration:
– When the molten metal enters the gaps between the sand grains, the
result would be a rough casting surface.
– It occurs when molten metal being cast tends to penetrate into the sand
grains and causes a fused aggregate of metal and sand on the surface
of the casting.
– Metal penetration causes rough castings. The metal seeps in between
the sand grains and gives a rough surface on the casting. Such castings
are difficult to clean because sand grains are held by little fingers of
metal.
– Causes:
• Improper ramming of sand.
• Excessive pouring temperature which increases the fluidity of
metal.
– Remedies: This defect can be eliminated by fine sand and hard
ramming the sand.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting defects: Metal penetration

Figure. Metal penetration and veining. (Penetration caused by an open sand veining caused
by metal penetration into cracked sand)
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting defects (moulding material defects)
• Fusion:
– This is caused by the fusion of sand grains with the molten metal,
giving a brittle, glassy appearance on the casting surface.
– Causes:
• Using moulding sand of low strength.
• Improper ramming of sand.
– Remedies:
• This defect can be eliminated by sand of proper strength and the
sand should be properly rammed in.
• Runout :
– A run out is caused when the molten metal leaks out of the mould.
– Causes:
• This may be caused either due to faulty mould making or
because of the faulty moulding flask.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (moulding material defects)
• Drop:
– A crush or drop occurs when part of the sand mould is crushed or
drops into the mold cavity.
– The dropping of loose moulding sand or lumps normally from the
cope surface into the mould cavity is responsible for this defect.
– This is essentially, due to improper ramming of the cope flask.
– Sometimes during casting upper surface of the mold cracks and
pieces of sands fall into the molten metal, this is known as drop.
– Causes:
• Using moulding sand of low strength.
• Improper ramming of sand.
– Remedies:
• This defect can be eliminated by sand of proper strength and the
sand should be properly rammed in.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (moulding material defects)
• Swell:
– Under the influence of the metallostatic forces, the mould wall
may move back causing a swell in the dimensions of the casting.
– It is a localized enlargement of the casting due localized
enlargement of the mould by molten metal pressure.
– Causes:
• Defective or improper ramming of the sand.
• Insufficient weighting of the mould during casting.
– Remedies:
• This defect can be eliminated by ensuring proper weight over
the moulding boxes and ramming the sand properly.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (moulding material defects)
• Swell:

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (Pouring metal defects)
• Misruns and cold shuts
– A misrun is a defect which lacks
completeness of the casting due
to the molten metal not filling
the mould cavity completely.
– A cold shut is caused when two
metal streams while meeting in
the mould cavity, do not fuse
together properly, thus causing a
discontinuity or weak spot in the
casting.
– A cold shut is an external defect
formed due to improper fusion
of two streams of molten metal
poured in the cavity.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (Pouring metal defects)
• Misruns and cold shuts
– Causes:
• Improper gating systems.
• Slow and intermittent
pouring.
• Poor fluidity of metal.
– Remedies:
• To eliminate these defects,
the gating system should be
properly designed and the
pouring should be controlled
suitably.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (Pouring metal defects)
• Slag inclusions or Honey Combing:
– During the melting process, flux is added to remove the
undesirable oxides and impurities present in the metal.
– It is an external defect consisting of number of small cavities in
close proximity.
– Causes:
• Suspended dirt in molten metal.
• Incorrect gating and poor fluxing of metal.
– Remedies:
• This defect can be avoided by preventing the slag from
entering along with the molten metal.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (Metallurgical defects)
• Hot tears:
– Since metal has low strength at higher temperatures, any unwanted cooling
stress may cause the rupture of the casting.
– It is an external or internal cracks occurring immediately after the metal have
solidified, resulting from hindered contraction.
– Causes:
• Abrupt changes in sections of the casting.
• Poor collapsibility of the mould and core materials, which places extra stress
on certain parts.
– Remedies:
• This defect can be eliminated by ensuring proper casting design and using
mould and core material having proper collapsibility.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects: Hot tears

Figure. Hot tear. (Caused by too high hot strength of the molding sand)

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting defects (mould preparation defects)
• mould Shifts:
• It is an external defect due to mismatching of the top and bottom half of the casting,
usually at the parting line.
– Causes:
• Misalignment of pattern parts.
• Misalignment of moulding box.
– Remedies:
• This defect can be eliminated by ensuring proper alignment of the pattern,
moulding boxes.
• Core Shifts:
– It is an variation of the dimensions of the casting due variation in position or size
of the core.
– Causes:
• Misalignment of cores.
• Undersized or oversized core or core prints.
– Remedies:
• This defect can be eliminated by placing the core properly in the mould and
using accurate size cores or core prints.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting defects

excessive flash

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Cleaning of casting
• After the metal has solidified and cool in the mold.
• These molds go to a shake out station where the sand and casting are dumped
from the flask.
• The casting are shaken free from the molding and some dry sand cores are
knocked out.
• This process of shake out is called the cleaning of castings.
• Actually shake out is done by two methods, manually or mechanically.
• Generally mechanical shake out are used for large scale work.
• This unit consists of heavy mesh screen fixed to a vibrating frame.
• The screen vibrate mechanically and quick separation of sand from other parts.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

FETTLING
• FETTLING.
• The complete process of cleaning of castings called fettling.
• It involves the removal of the cores, gates, sprues, runners, risers and chipping of
any of unnecessary projections on the surface of the castings.
• The fettling operation may be divided in to different stages.
• Knocking out of dry sand cores. Dry sand cores may be removed by knocking
with iron bar.
• For quick knocking pneumatic or hydraulic devices are empolyed, this method is
used for small, meduim work. For large castings the hydro blast process is mostly
employed.
• Fettling - the removal of feeders and excess material from a casting - is the first
stage of finishing a casting. The metal removal is often achieved using manual
cutting or grinding. However, more emphasis is being placed on automatic
fettling, whereby the casting is placed in a machine programmed to remove
materials from specific areas. The method of fettling must be taken into account
at the initial casting design stage, so that the process is fast and efficient.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Removal of gates and risers
• With chipping hammer. It is particularly suited in case of grey iron castings and
brittle materials.
• The gates and risers can easily be broken by hitting the hammer.
• With cutting saw. These saws may be hand saw and power saw are used for
cutting the ferrous like steel, melable iron and for non ferrous materials except
aluminum.
• Mostly the hand saws are used for small and medium but when power and used
for large work.
• With flame cutting. This type of method is specially used for ferrous materials of
large sized castings where the risers and gates are very heavy.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

For sprue cutting.
• The shear is specially made tool on punch press base .
• In this there is heavy matching steel jaws are fitted. It is mostly used for melable
iron soft and medium , hard steel brass bronze Al, Mg. Shears are limited to small
work ,but are very fast and economical.
• With abrasive cut of machine. These machines can work with all metals but are
specially designed for hard metals which can not saw or sheared also where
flame cutting and chipping is not feasible. It is more expensive than other
methods.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Removal of fins, rough spots and un wanted projections.
• The fins and other small projections may easily be chipped off with the help of
either hand tools or pneumatic tools.
• But for smoothing the rough cut gate edges either the pedestal or swing frame
grinder is used depends upon the size of castings.
• For cleaning the sand particles sticking to the casting surface sand blasting is
normally used.
• In this method the casting is kept in a closed chamber and a jet of compressed air
with a blast of sand grains or steel grit is directed against the casting surface
which thoroughly cleans the casting surface.
• The shots used are either chilled cast iron grit or steel grit. Chilled iron is less
expensive but is likely to be lost quickly by fragmentation.
• An other use full method for cleaning the casting surface is the tumbling. This is
an oldest machine method for cleaning the casting surfaces. In this method the
castings are put in large sheet shell or barrel along with the castings and small
piece of white cast iron called stars. The barrel is supported on horizontal turn
ions and is related at the speed varying from 25-30rpm for 15-30 minutes. It
causing the castings to tumble over to another, rubbing against the castings and
the stars. Thus by continuous peeing action not only are the castings cleaned but
also sharp edges are eliminated.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Shell Molding
• The sand used in shell moulding are dry and fine sand; silica sand and Zircon
sand or combination of the two are used.
• The sand is mixed with phenolic resin (phenol formaldehyde) and other additives
(to improve surface finish and avoid thermal cracking during pouring)
• The various additives used are (coal dust, manganese dioxide, calcium carbonate,
magnesium silicoflouride, ammonium borofluoride etc. Some lubricants are also
added to increase the flowability of the sand (calcium stearate , zinc stearate)
• A silicon based releasing agent is normally sprayed on the heated metal pattern as
releasing agent.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable mould with multiple use pattern (Shell molding)

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable mould with multiple use pattern (Shell molding)

(b) Pattern and dump box rotated

• Developed in the 1940’s
• Produces close dimensional
tolerances
• Good surface finish
• Low cost process
(c) Pattern dump box in position for the
investment

Common methods of making shell moulds.

(a) Pattern rotated and clamped

(d) Pattern and shell removed from dump box

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Shell moulding

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Shell moulding

Figures showing two different shell moulds

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Shell moulding: Sand
• The dry free flowing sand used in the shell mould must be completely free of
clay content.
• The grain size of the sand used in shell molding is generally in the range of 100-
150 mesh, as the shell casting process is recommended for castings that require
good surface finish.
• However, depending on the requirement of surface finish of the final casting, the
grain size of the sand can be ascertained.
• Also, if the grain size is very fine, it requires large amount of resins, making it
expensive.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Shell moulding: Resin and Catalyst
• The resins most widely used, are the phenol formaldehyde resins, which are
thermosetting in nature. Combined with sand, they give very high strength and
resistance to heat.
• The resin initially has excess phenol and acts like a thermoplastic material. In
order to develop the thermosetting properties of the resin, the coating of the sand
is done with resin and a catalyst (Hexa-methylene-tetramine, known as Hexa).
• The measure of resin is 4-6% of sand by weight, the catalysts 14-16% of sand by
weight.
• The curing temperature of the resin along with the catalysts is around 150o C and
the time required for complete curing is 50 – 65 seconds.
• The sand composition to be used in making various casting of different materials
can be seen from the relevant standards.
• The resins available are of water-bourn, flake, or the granular types.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Shell moulding
• The resin sand mix aggregate can be prepared by the following three ways.
• Hot coating process: in hot coating process the curing of resin takes place due to
the combined effect of heat as well as chemical action of the resin with the
catalyst. Once the curing is done, the cured sand is cooled at 40-50 degree
centigrade to prevent the lumps and agglomerates and to improve the flow-
ability.
• Warm coating process: In this process, different resin formulation (liquid
solvent solution) is used and curing takes place at around 80 degree centigrade.
The process is simpler than hot coating but the quantity of resin consumed is
larger.
• Cold coating process: In this process, the sand is first mixed with catalysts, then
the resin mixed with alcohol is added to the aggregate. The amount of resin
requirement is highest in comparison to the amount required in hot and warm
coating processes

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Shell moulding
• Phenol-Formaldehyde Resins:
• In manufacturing the shell sand, phenol, formaldehyde resin is used as a binder.
The form of resin may be liquid or flake type. Liquid resin is nothing but is a
resin dissolved in alcohol. Liquid resin is used for manufacturing shell sand by
either warm air process or by ignition process, whereas solid or flake resin is
used for hot coating process. Most of Indian manufacturers of shell sand use
liquid resin, because of the easiness of resins of the process. The following
properties of resins are generally checked as a acceptance criteria.
• Hexa Catalyst
• The phenol formaldehyde resins are thermoplastic in nature and require a
formaldehyde donor to cure at a certain temperature. Thus after blending of the
resin and the catalyst, it becomes thermo-set in nature and thus the formation of
shell molds and cores is accomplished. The catalyst used is a blend of hexa
methylene tetra-amine and a lubricant. Lubrication helps in the flowability of
shell sands. Hexa catalyst is available in the form of a fine powder.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Shell moulding
• Use of Additives
• Additives may be added to the sand aggregate to further enhance the surface
finish of the casting or two improve the strength of the mould or to develop the
resistance to thermal cracking and distortion. The recommended additives are
coal dust, manganese dioxide, calcium carbonate, ammonium boro-fluoride,
lignin and iron oxide. To improve the flowability of the sand and to permit easy
rlubricants are added in the resin sand aggregate. The common lubricants used
for such purpose is calcium or zinc stearate. emoval of shell from the pattern
plate, some

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Shell moulding
• Advantages:
• Better surface finishes are obtained.
• Machining of castings are reduced.
• The chances of blow holes or pockets are reduced since the holes are
highly permeable.
• Shells can be stored for long time.
• High dimensional accuracy can be obtained.
• Draft angles which are lower than the sand castings are required in
shell moulds. The reduction in draft angles may be from 50 to 75%
which considerably saves the material costs and the subsequent
machining costs.
• Also, very thin sections (upto 0.25 mm) of the type of air cooled
cylinder heads can be readily made by the shell moulding because of
the higher strength of the sand used for moulding.
• Permeability of the shell is high and therefore no gas inclusions occur.
• Very small amount of sand needs to be used.
• Mechanisation is readily possible because of the simple processing
involved in shell moulding.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Shell moulding
• Limitations:
• The metal pattern is costlier than the wooden one. The patterns are very
expensive and therefore are economical only if used in large scale
production.
• The size of the casting obtained by shell moulding is limited. Generally
castings weighing upto 200 kg can be made, though in smaller quantity.
castings upto a weight of 450 kg were made.
• Highly complicated shapes cannot be obtained.
• More sophisticated equipment is needed for handling the shell
mouldings such as those required for heated metal patterns. High
equipment cost.
• High resin cost.
• Uneconomical for small production lots.
• Relative inflexibilities in gating and risering systems.
• Applications:
• The most common application is for automobile parts castings in grey cast iron
and aluminum. Cylinder and cylinder heads of air cooled IC engines, small
crank shafts, automotive transmission parts, bevel gears, brake beam etc.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Expendable mould with single use pattern: Investment Casting- lost
wax process

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable mould with single use pattern: Investment Casting- lost
wax process

FIGURE :Schematic illustration

of investment casting (lost-wax
process). Castings by this
method can be made with very
fine detail and from a variety of
metals. Source: Steel Founders’
Society of America.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Schematic illustration of investment casting
1. WAX INJECTION : Wax replicas of the desired
castings are produced by injection moulding. These
replicas are called patterns.

2. ASSEMBLY : The patterns are attached to a central

wax stick, called a sprue, to form a casting cluster
or assembly.

3. SHELL BUILDING : The shell is built by immersing

the assembly in a liquid ceramic slurry and then into a
bed of extremely fine sand. Up to eight layers may be
applied in this manner.

4. DEWAX : Once the ceramic is dry, the wax is melted

out, creating a negative impression of the assembly
within the shell.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Schematic illustration of investment casting
• 5. CONVENTIONAL CASTING: In the
conventional process, the shell is filled with molten
metal by gravity pouring. As the metal cools, the
parts and gates, sprue and pouring cup become one
solid casting.

• 6. KNOCKOUT: When the metal has cooled and

solidified, the ceramic shell is broken off by vibration
or water blasting.

• 7. CUT OFF: The parts are cut away from the central
sprue using a high speed friction saw.

• 8. FINISHED CASTINGS: After minor finishing

operations, the metal castings--identical to the original
wax patterns--are ready for shipment to the customer.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable mould with single use pattern: Investment Casting- lost
wax process
• Investment casting is also known as the lost wax process.
• This process is one of the oldest manufacturing processes.
• The Egyptians used it in the time of the Pharaohs to make gold jewelry
(hence the name Investment) some 5,000 years ago.
• Intricate shapes can be made with high accuracy.
• In addition, metals that are hard to machine or fabricate are good candidates
for this process.
• It can be used to make parts that cannot be produced by normal
manufacturing techniques, such as turbine blades that have complex shapes,
or airplane parts that have to withstand high temperatures.
• The mould is made by making a pattern using wax or some other material
that can be melted away.
• This wax pattern is dipped in refractory slurry, which coats the wax pattern
and forms a skin.
• This is dried and the process of dipping in the slurry and drying is repeated
until a robust thickness is achieved.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable mould with single use pattern: Investment Casting- lost
wax process
• After this, the entire pattern is placed in an oven and the wax is melted away.
• This leads to a mould that can be filled with the molten metal.
• Because the mould is formed around a one-piece pattern, (which does not
have to be pulled out from the mould as in a traditional sand casting process),
very intricate parts and undercuts can be made.
• The materials used for the slurry are a mixture of plaster of Paris, a binder
and powdered silica, a refractory, for low temperature melts.
• For higher temperature melts, sillimanite an alumina-silicate is used as a
refractory, and silica is used as a binder.
• Depending on the fineness of the finish desired additional coatings of
sillimanite and ethyl silicate may be applied.
• The shell thickness varies from 6 to 15 mm.
• The mould thus produced can be used directly for light castings, or be
reinforced by placing it in a larger container and reinforcing it more slurry.
• Just before the pour, the mould is pre-heated to about 100-1000 ºC to remove
any residues of wax, harden the binder.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable mould with single use pattern: Investment Casting- lost
wax process
• The pour in the pre-heated mould also ensures that the mould will
fill completely.
• Pouring can be done using gravity, pressure or vacuum conditions.
• Attention must be paid to mould permeability when using pressure,
to allow the air to escape as the pour is done.
• The types of materials that can be cast are Aluminum alloys,
Bronzes, tool steels, stainless steels, Stellite, and precious metals.
• Parts made with investment castings often do not require any
further machining, because of the close tolerances that can be
achieved.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Investment Casting- lost wax process: A video

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable mould with single use pattern: Investment Casting- lost
wax process
• Advantages:
• High dimensional accuracy.
• A very smooth surface can be achieved.
• Extremely thin sections, to the extent 0.75mm, can be cast
successfully. Very fine details and thin sections can be produced
by this process, because the mould is heated before pouring.
• Complex shapes which are difficult to produce by any other
method are possible since the pattern is withdrawn by melting it.
• Suitable for mass production of small sized castings.
• Castings produced by this process are ready for use with little or
no machining required. This is particularly useful for those hard-
to-machine materials such as nimonic alloys.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable mould with single use pattern: Investment Casting- lost
wax process
• Limitations:
• The process is normally limited by the size and mass of the
casting. The upper limit on the mass of a casting may be of the
order of 5 kg.
• This is a more expensive process because of larger manual labour
involved in the preparation of the pattern and the mould.
• Production rate is slow.
• Applications:
• This process is used for casting of turbine blades and parts of
automobile, wave guides for radars, triggers for firearms, SS valve
bodies etc.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Expendable-Pattern Casting (IN SHORT)
• Polystyrene beads are placed in a preheated die
• The polystyrene bead expand to fix the die
• The die is cooled and the polystyrene pattern is removed
• The polystyrene pattern is placed in a mould with support sand
• The polystyrene pattern evaporates with contact of molten metal to form a cavity

Schematic illustration of the expendable pattern casting process also known as lost
foam or evaporative casting.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Evaporative Pattern Casting (EPC)
• The evaporative-pattern casting process uses a polystyrene pattern, which
evaporates upon contact with molten metal to form a cavity for the casting; this
process is also known as lost-foam casting and falls under the trade name full-
mold process. It has become one of the more important casting processes for
ferrous and nonferrous metals, particularly for the automotive industry.
• In EPC process, pattern is usually made of expandable polystyrene (EPS). The
use of a polystyrene pattern increases dimensional accuracy, and gives improved
casting quality, compared to conventional casting.
• Patterns are produced in EPS (Encapsulated Polystyrene), the pattern receives a
sprue or feeder system (also of EPS) and can be either placed directly into loose
dry sand, or invested into a ceramic slurry. The slurry is air dried or in a low
temp oven (but the foam pattern is retained).
• In this process, polystyrene beads containing 5 to 8% pentane (a volatile
hydrocarbon) are placed in a preheated die that is usually made of aluminum. The
polystyrene expands and takes the shape of the die cavity. Additional heat is
applied to fuse and bond the beads together. The die is then cooled and opened,
and the polystyrene pattern is removed. Complex patterns also may be made by
bonding various individual pattern sections using hot-melt adhesive.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Evaporative Pattern Casting
• The pattern is coated with a refractory slurry, dried, and placed in a flask.
• The flask is then filled with loose, fine sand, which surrounds and supports the
pattern (Fig) and may be dried or mixed with bonding agents to give it additional
strength.
• In this process, the sand mold contains no binder and moisture and hence the
refractoriness of the mold is entirely dependent upon the molding sand.
• An attempt is made to bind the EPC mold by creating vacuum in the mold while
mold is sealed from the both end by polyethylene film.
• Any type of molding sand can be used for the process as long as the sand resists
the temperature of the molten metal being poured. Silica sand, zircon sand,
olivine sand and chromites can be used as molding sand.
• Due to high degree of sand reclamination in EPC process, expensive sands such
as zircon or chromites can be used.
• The sand is compacted periodically, without removing the polystyrene pattern;
then the molten metal is poured into the mold.
• The molten metal vaporizes the pattern and fills the mold cavity, completely
replacing the space previously occupied by the polystyrene.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Evaporative Pattern Casting

Figure: Schematic illustration of the expandable-pattern casting process, also known as lost-
foam or evaporative casting.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
EVAPORATIVE PATTERN CASTING: PROCEDURE
1. The process of EPC starts with the pre-expansion of polystyrene beads. Once
these pre-expanded beads get stabilized, pattern sections are formed by blowing
them into a mold. A cycle of steam is used to fully expand and make the beads
fuse in the mold itself.
2. Clusters are formed through assembly of the pattern sections using glue. The
gating systems are also similarly glued and attached.
3. Ceramic coating is used to cover the foam cluster. The coating acts as a barrier
preventing the penetration and sand erosion during pouring.
4. Once the coating gets dried, the cluster is placed in a flask along with backing of
the bonded sand. Any suitable sand can be used as long as it resists the
temperature of the molten metal being poured. Silica sand, zircon sand, olivine
sand and chromites can be used as molding sand.
5. In order to ensure uniform and proper compaction, a vibrating table is used in
the mold compaction. After completing this process, the cluster is packed in a
flask and the mould is set ready for getting poured.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Evaporative Pattern Casting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Evaporative Pattern Casting
The flow velocity of the molten metal in the mold depends on the rate of degradation
of the polymer. Studies have shown that the flow of the metal is basically laminar,
with Reynolds numbers in the range of 400 to 3000. The velocity of the molten
metal at the metal-polymer pattern front (interface) is in the range of 0.1 to 1.0 mfs
and can be controlled by producing patterns with cavities or hollow sections. Thus,
the velocity will increase as the molten metal crosses these hollow regions, similar to
pouring the metal into an empty cavity. Because the polymer requires considerable
energy to degrade, large thermal gradients are present at the metal-polymer interface.
In other words, the molten metal cools faster than it would if it were poured directly
into an empty cavity. Consequently, fluidity is less than in sand casting. This has
important effects on the microstructure throughout the casting and also leads to
directional solidification of the metal. Polymethylmethacrylate (PMMA) and
polyalkylene carbonate also may be used as pattern materials for ferrous castings.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Evaporative Pattern Casting
The evaporative-pattern process has a number of advantages over other casting
methods:
• The process is relatively simple because there are no parting lines, cores, or riser
systems. Hence, it has design flexibility.
• Inexpensive flasks are satisfactory for the process.
• Polystyrene is inexpensive and can be processed easily into patterns having
complex shapes, various sizes, and fine surface detail.
• The casting requires minimal finishing and cleaning operations.
• The process can be automated and is economical for long production runs.
However, major factors are the cost to produce the die used for expanding the
polystyrene beads to make the pattern and the need for two sets of tooling.
Disadvantages - Pattern coating requires additional labour and material costs,
patterns require care as they can be fragile due to construction, Strict safety
procedures to be followed when handling loose sand post pouring. The last item
applies to all loose sand handling with regard to the hazards of Silicosis, but
especially when handling sand that has burnt EPS covering the grains. The strong
chemical stench of the sand screams of future respiratory ailments if caution is not
exercised.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Evaporative Pattern Casting of an Engine Block

(a) (b)

Figure (a) Metal is poured into mold for lost-foam casting of a 60-hp. 3-cylinder marine
engine; (b) finished engine block. Source: Courtesy of Mercury Marine.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Evaporative Pattern Casting- process parameters
• Pattern density and bead size: Density and bead size play important role in
evaporative pattern casting process. A low density pattern is required to minimize
the amount of gas evolved during vaporization of the pattern. Since the gas must
permeate through the coating, sand and vent into the atmosphere. If the gas forms
faster than it can vent, a defective casting will result. Gas formation is a function
of pattern density and metal pour temperature. If pattern density is increased,
more gas formed at a constant pour temperature. Steel castings generally required
a lower density pattern than gray, malleable or ductile iron, ferrous castings
require a lower density than copper alloys, which in turn need a lower density
than aluminum castings.
• Requirement of refractory coating material: Coatings are integral part of
casting production, since they provide a good quality surface of castings without
glued and baked sand. Highly permeable coating is used for rougher sand while
medium and low permeable coating is used for finer sand. If rougher sand is used
for mould making and a high casting temperature, then the refractory coating
layer should be thicker.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Evaporative Pattern Casting- process parameters
• Selection of coating material: There are several kinds of evaporative pattern
coating with different thermo-physical characteristic, which are specially
designed to meet number of requirements of the evaporative pattern casting
process. For the cast iron, a coating based on iron powder has been found
successful in preventing metal penetration problems. The high pouring
temperature ranges of cast iron and steel usually dictate the selection of a silica or
mullite type refractory. Many coating materials that can be used are zircon flour,
kaolin etc.

• Reference: Sudhir Kumar, Pradeep Kumar, H.S. Shan, “Effect of evaporative

pattern casting process parameters on the surface roughness of Al–7% Si alloy
castings”, Journal of Materials Processing Technology 182 (2007) 615–623

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

EPC: ADVANTAGES
• In the EPC process, no cores are required making it the most advantageous.
• No requirement for binders or other additives, as it is a binder less process.
• Complete sand reclamation is possible using very simple and inexpensive
techniques.
• Sand shake out is easy as the sand is unbounded.
• Since the pattern used in EPC process is one piece, hence no parting line and
since cores are eliminated, hence no core prints. Also, no mismatch, core shift
because of the mentioned reasons
• Improved casting quality. Close tolerances are possible.
• The EPC is an environmentally favorable process.
• As it is a binder less process, the efforts on cleaning the molded sand are
virtually nil. Therefore, the EPC process is viewed as a value-added process
rather than a substitute for sand casting.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

EPC: DISADVANTAGES
• Since every casting requires a new pattern, it is a costly process.
• There is a limitations on the minimum section thickness of the pattern.
• Quality of the casting fully depends upon the quality of the pattern.
• As the sand is unbounded, during pouring, due to the difference in the
evaporation rates of the pattern material and the flow rate of the metal, the sand
falls down in the generated cavity generated, thereby leading to a defective
casting.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

VARIATIONS OF PERMANENT-mould CASTING
• Vacuum Permanent-mould Casting: Not to be confused with vacuum
moulding, this process is a variation of low-pressure casting in which a vacuum is
used to draw the molten metal into the mould cavity. The general configuration
of the vacuum permanent mould casting process is similar to the low-pressure
casting operation. The difference is that reduced air pressure from the vacuum in
the mould is used to draw the liquid metal into the cavity, rather than forcing it by
positive air pressure from below. There are several benefits of the vacuum
technique relative to low-pressure casting: air porosity and related defects are
reduced, and greater strength is given to the cast product.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Vacuum Casting
1. Mixture of fine sand and
urethane is moulded over
metal dies a cured with
amine vapor
2. The mould is partially
immersed into molten metal
held in an induction furnace
3. The metal is melted in air or
in a vacuum
4. The molten metal is usually
55 C above the liquidus
temperature – begins to
solidify within a fraction of a
second
FIGURE: Schematic illustration of the vacuum-
5. Alternative to investment,
casting process. Note that the mould has a
shell-mould, and green-sand bottom gate. (a) Before and (b) after immersion
casting of the mod into the molten metal. Source: After
6. Relatively low cost R. Blackburn.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Pressure Casting

(a) The bottom-pressure casting process utilizes graphite moulds for the productin of
steel railroad wheels. (b) Gravity pouring method of casting a railroad wheel. Note
that the pouring basin also serves as a riser.
•Used a graphite or metal mould
•Molten metal is forced into the mould by gas pressure
•The pressure is maintained until the metal solidifies in the mould
•Used for high-quality castings
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Multi use moulds: Die casting
• The term die is used for permanent mould.
• In this process the molten metal is forced into the permanent mould
(dies) under high pressure.
• The molten metal fills the entire die, including the minute details.
• On solidification the casting is taken out.
• Thus High pressure die casting uses a piston to inject the molten
metal into the die.
• This greatly speeds the process, and therefore increases production.
• This results in a more uniform part, generally good surface finish
and good dimensional accuracy, as good as 0.2 % of casting
dimension.
• For many parts, post-machining can be totally eliminated, or very
light machining may be required to bring dimensions to size.
• There are two types of high pressure die casting: hot chamber and
cold chamber.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Multi use moulds: Die casting
• Hot chamber die casting:
• The melting unit of the metal forms an integral part of the machine.
• The plunger is made up of refractory material.
• When the plunger is raised, it uncovers an opening in the cylinder
wall, through which molten metal enters, filling the cylinder.
• The molten metal is forced into the die either by hydraulic pressure
or by air pressure applied to the plunger.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Die casting
• As soon as the metal solidifies, the pressure on the metal is relieved
and the plunger travels upwards to its original position.
• The casting is ejected from the die by means of ejector pins.
• This process is particularly suitable for lead, tin and zinc alloys.
• Hot chamber die casting cannot be used for metals having high
melting temperatures.
• Also it cannot be used to cast metals like aluminum, copper etc.
which will react with steel at high temperature.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Die Casting in Hot-Chamber Process

FIGURE: Sequence of steps in die casting of a part in the hot-chamber process.

Source: Courtesy of Foundry Management and Technology.
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Multi use moulds: Die casting

Hot chamber die casting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Die casting
• Cold chamber die casting:
• In cold chamber die casting the plunger is horizontal and is driven
by air or hydraulic pressure to force the molten metal in to the die.
• As soon as the ladle is emptied, plunger moves forward and forces
the metal into the cavity of the die.
• After the metal solidifies, the core is with drawn, and then the die is
opened.
• Ejector pins are employed to remove the casting automatically from
the die.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Die casting
• The cold chamber die casting is particularly suitable for metal such
as aluminum alloys, magnesium, copper, which cannot be cast in
hot chamber machines due to reactivity with molten aluminum and
steel.
• High melting temperature alloys of non-ferrous type are best die
cast in cold chamber die casting.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Die Casting in Cold-Chamber Process

FIGURE: Sequence of operations in die casting of a part in the cold-chamber

process. Source: Courtesy of Foundry Management and Technology.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Die casting

Operation sequence of cold chamber process.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Multi use moulds: Die casting

Construction of a cold chamber machine

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Various types of cavities in a die casting die.

a) Single – cavity die

b) Multiple – cavity die

c) Combination die

d) Unit die

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Die-Casting Alloys

ALLOY ULTIMATE YIELD ELONGA‐TION APPLICATIONS

TENSILE STRENGTH in 50 mm
STRENGTH (MPa) (%)
(MPa)
Aluminum 380 320 160 2.5 Appliances, automotive components, electrical
(3.5 Cu‐8.5 Si) motor frames and housings, engine blocks.

13 (12 Si) 300 150 2.5 Complex shapes with thin walls, parts requiring
strength at elevated temperatures
Brass 858 (60 Cu) 380 200 15 Plumbing fixtures, lock hardware, bushings,
ornamental castings
Magnesium AZ91B (9 Al – 0.7 Zn) 230 160 3 Power tools, automotive parts, sporting goods
Zinc No. 3 (4 Al) 280 ‐ 10 Automotive parts, office equipment, household
utensils, building hardware, toys
5 (4 Al – 1 Cu) 320 ‐ 7 Appliances, automotive parts, building hardware,
business equipment

TABLE : Properties and typical applications of common die-casting alloys.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Die casting
• Advantages of die casting:
• Very high production rates are possible. Typical rate could be
200 pieces per hour since the process is completely automated.
• Thin sections can be cast. Very small thicknesses can be easily
filled because the liquid metal is injected at high pressure.
Surface of about 0.8 microns can be achieved.
• Close dimensional tolerances of the order of 0.0025mm is
possible.
• Because of the use of the movable cores, it is possible to obtain
fairly complex castings.
• Fine details may be produced.
• Less floor space is required.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Die casting
• Limitations of die casting:
• Not economical for small runs. The dies and the machines are
very expensive and therefore, economy in production is possible
only when large quantities are produced.
• Only economical for non-ferrous alloys.
• Due to high temperature of molten metal, die life decreases.
• The air in the die cavity gets trapped inside the casting and is
therefore a problem often with the diecastings.
• The maximum size of the casting is limited. The normal sizes are
under 4 kg with a maximum of the order of 15 kg because of the
limitation on the machine capacity.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Centrifugal casting
• Centrifugal casting are of three types:
– True centrifugal casting: Long moulds are rotated about a
horizontal axis. This can be used to make long axial parts such
as seamless pipes.
– Semi centrifugal casting: Parts with a wide radial parts. Parts
such as wheels with spokes can be made with this technique
– Centrifuging: The moulds are placed a distance from the
center of rotation. Thus when the poured metal reaches the
moulds there is a high pressure available to completely fill the
cavities. The distance from the axis of rotation can be increased
to change the properties

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Centrifugal casting (True centrifugal casting)
• A mould is set up and rotated along a inclined or horizontal (200-
1000 rpm) axis.
• The mould is coated with a refractory coating.
• While rotating molten metal is poured in.
• The metal that is poured in will then distribute itself over the
rotating wall.
• During cooling lower density impurities will tend to rise towards
the center of rotation.
• After the part has solidified, it is removed and finished.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Centrifugal Casting Process

FIGURE: Schematic illustration of the centrifugal casting process. Pipes, cylinder

liners, and similarly shaped parts can be cast by this process.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Centrifugal casting (True centrifugal casting)
• Advantages:
• The mechanical properties of centrifugally cast jobs are better
compared to other processes, because the inclusions such as slag
and oxides gets segregated towards the centre and can be easily
removed by machining. Also, the pressure acting on the metal
throughout the solidification, causes the porosity to be eliminated
giving rise to dense metal.
• Good uniform metal properties
• No sprues/gates to remove
• The outside of the casting is at the required dimensions
• Lower material usage
• No cores are required for making concentric holes in the case of
true centrifugal casting.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Centrifugal casting (True centrifugal casting)
• Disadvantages:
• Extra equipment needed to spin mould
• The inner metal of the part contains impurities .
• Only certain shapes which are axi-symmetric and having
concentric holes are suitable for true centrifugal casting.
• The equipment is expensive and thus is suitable only for large
quantity production.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Semi-centrifugal and centrifuging Casting Process

FIGURE: (a) Schematic illustration of the semicentrifugal casting process. (b) Schematic
illustration of casting by centrifuging. The moulds are placed at the periphery of the machine,
and the molten metal is forced into the moulds by centrifugal forces.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Centrifugal casting (Semi centrifugal casting)

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Centrifugal casting (Semi centrifugal casting)
• In this method, centrifugal force is used to produce solid castings, as in Figure,
rather than tubular parts. The rotation speed in semi-centrifugal casting is usually
set so that G-factors of around 15 are obtained, and the moulds are designed with
risers at the center to supply feed metal. Density of metal in the final casting is
greater in the outer sections than at the center of rotation. The process is often
used on parts in which the center of the casting is machined away, thus
eliminating the portion of the casting where the quality is lowest. Wheels and
pulleys are examples of castings that can be made by this process.

FIGURE: Semicentrifugal casting.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Multi use moulds: Centrifugal casting (Centrifuging)

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Centrifugal casting (Centrifuging)
• In centrifuge casting, the mould is designed with part cavities located away from
the axis of rotation, so that the molten metal poured into the mould is distributed
to these cavities by centrifugal force. The process is used for smaller parts, and
radial symmetry of the part is not a requirement as it is for the other two
centrifugal casting methods.

FIGURE: (a) Centrifuge casting—centrifugal force causes metal to flow to the mould
cavities away from the axis of rotation; and (b) the casting.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Continuous casting
• The traditional method of making Steel and Aluminum includes
making ingots from molten metal.
• However, continuous casting has become very popular for
productivity reasons.
• Continuous steel casting produces higher quality steel and
aluminum at reduced cost; this is because there are:
– No ingots with uneven alloying; giving a better product.
– No moulds from which the ingot must be separated
– Continuous casting commonly takes place in processes where
long metal slabs must be created continuously.
– The process involves a ladle car that delivers molten steel to a
tundish. This large container then allows a continuous flow of
steel to exit into two or more container/”nozzles”.
– Water mist or spray cooling is used to solidify the steel at
appropriate rates..
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Multi use moulds: Continuous casting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Continuous casting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Multi use moulds: Continuous casting

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Comparison of casting processes

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

mould Filling

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Design Rules
•Decrease the maximum wall thickness of a part to shorten the cycle time (cooling time
specifically) and reduce the part volume
INCORRECT CORRECT

Part with thick walls Part redesigned with thin walls

•Uniform wall thickness will ensure uniform cooling and reduce defects. A thick section,
often referred to as a hot spot, causes uneven cooling and can result in shrinkage, porosity, or
cracking.
INCORRECT CORRECT

Non-uniform wall thickness (t1 ≠ t2) Uniform wall thickness (t1 = t2)
Source: http://www.custompartnet.com/wu/SandCasting
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting Design Rules
•Corners : Round corners to reduce stress concentrations and fracture
•Inner radius should be at least the thickness of the walls

INCORRECT CORRECT

Sharp corner Rounded corner

•Draft : Apply a draft angle of 2° - 3° to all walls parallel to the parting direction to facilitate
removing the part from the mould.
INCORRECT CORRECT

No draft angle Draft angle ()

Source: http://www.custompartnet.com/wu/SandCasting
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting Design Rules
• Be Careful With Consideration To L,T,V,Y and + junctions: Due to the nature of the
geometry of these sections it is likely that they will contain an area where the metal
casting's solidification is slower than the rest of the junction. These hot spots are circled in
red in Figure 18. They are located such that the material around them, which will undergo
solidification first, will cut off the hot spots from the flow of molten metal. The flow of
casting material must be carefully considered when manufacturing such junctions. If there
is some flexibility in the design of the metal casting and it is possible you may want to
think about redesigning the junction. These should reduced the likelihood of the formation
of hot spots.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Design Rules
• Heat Masses: Avoid large heat masses in locations distant to risers. Instead,
locating sections of the casting with low V/A ratios further away from the risers
will insure a smooth solidification of the casting.

Source: http://thelibraryofmanufacturing.com/metalcasting_troubleshooting.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Design Rules
• Sections of the Casting: The flow of material is very important to the
manufacturing process. Do not feed a heavy section through a lighter one.

Source: http://thelibraryofmanufacturing.com/metalcasting_troubleshooting.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Design Rules
• Prevent Planes of Weakness: When metal castings solidify, columnar grain
structures tend to develop, in the material, pointing towards the center. Due to
this nature, sharp corners in the casting may develop a plane of weakness. By
rounding the edges of sharp corners this can be prevented.

Source: http://thelibraryofmanufacturing.com/metalcasting_troubleshooting.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Design Rules
• Reduce Turbulence: When manufacturing a metal casting, turbulence is always
a factor in our flow of molten metal. Turbulence, as covered earlier in the pouring
section, is bad because it can trap gases in the casting material and cause mould
erosion. Although not altogether preventable in the manufacturing process,
turbulence can be reduced by the design of a gating system that promotes a more
laminar flow of the liquid metal. Sharp corners and abrupt changes in sections
within the metal casting can be a leading cause of turbulence. Their affect can be
mitigated by the employment of radii.

Source: http://thelibraryofmanufacturing.com/metalcasting_troubleshooting.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Design Rules
• Connection Between Riser and Casting Must Stay Open: Riser design is very
important in metal casting manufacture. If the passage linking the riser to the
metal casting solidifies before the casting, the flow of molten metal to the casting
will be blocked and the riser will cease to serve its function. If the connection has
a larger cross sectional area it will decrease its time to freeze. Good
manufacturing design, however, dictates that that we minimize this cross section
as much as possible to reduce the waste of material in the casting process. By
making the passageway short we can keep the metal in its liquid state longer
since it will be receiving more heat transfer from both the riser and the casting.

Source: http://thelibraryofmanufacturing.com/metalcasting_troubleshooting.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Design Rules
• Tapered Down Sprue:
• Flow considerations for our metal casting manufacture begin as soon as the
molten metal enters the mould. The liquid metal for the casting travels from the
pouring basin through the down sprue,. As it goes downward it will pick up
speed, and thus it will have a tendency to separate from the walls of the mould.
The down sprue must be tapered such that continuity of the fluid flow is
maintained. Remember the fluid mechanics equation for continuity A1V1=A2V2.
Where V is the velocity of the liquid and A is the cross sectional area that it is
traveling through. If you are casting for a hobby and/or just can not make these
measurements, just remember it would be better to err on the side of making A2
smaller, provided your pouring rate does not become too slow. In other words
taper a little more and just adjust your pouring of the casting so that you keep a
consistent flow of liquid metal.

Source: http://thelibraryofmanufacturing.com/metalcasting_troubleshooting.html

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Design Rules
• Ingate Design: The ingate is another aspect of manufacturing design that relates
to the flow of metal through the casting's system. The ingate, is basically where
the casting material enters the actual mould cavity. It is a crucial element, and all
other factors of the metal casting's mould design are dependent on it. In the
location next to the sprue base the cross sectional area of the ingate is reduced
(choke area). The cross sectional reduction must be carefully calculated. The
flow rate of casting material into the mould can be controlled accurately in this
way. The flow rate of the casting metal must be high enough to avoid any
premature solidification. However, you want to be certain that the flow of molten
material into the mould does not exceed the rate of delivery into the pouring
basin and thus ensure that the casting's gating system stays full of metal
throughout the manufacturing process.

Source: http://thelibraryofmanufacturing.com/metalcasting_troubleshooting.html
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting Design Rules
• Use of Chills: Sometimes we may have an area of the metal casting that will
need to solidify at a faster rate in order to ensure that directional solidification
occurs properly. Manufacture planning, and design of flow and section locations
within the mould may not be sufficient. To accelerate the solidification of a
section like this in our casting, we may employ the use of chills. Chills act as heat
sinks, increasing the cooling rate in the vicinity where they are placed.
• Chills are solid geometric shapes of material, manufactured for this purpose.
They are placed inside the mould cavity before pouring. Chills are of two basic
types. Internal chills are located inside the mould cavity and are usually made of
the same material as the casting. When the metal solidifies the internal chills are
fused into the metal casting itself. External chills are located just outside of the
casting. External chills are made of a material that can remove heat from the
metal casting faster than the surrounding mould material. Possible materials for
external chills include iron, copper, and graphite.

Source: http://thelibraryofmanufacturing.com/metalcasting_troubleshooting.html
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting Design Rules
• Insulate Risers: Since the riser is the reservoir of molten material for the casting,
it should be last to solidify. Insulating the top will greatly reduce cooling in the
risers from the steep temperature gradient between the liquid metal of the casting,
and the the room temperature air.
• Consider V/A Ratios: In casting manufacture, V/A ratio stands for volume to
surface area or mathematically (volume/surface area). When solidification of a
casting begins a thin skin of solid metal is first formed on the surface between the
casting and the mould wall. As solidification continues the thickness of this skin
increases towards the center of the liquid mass. Sections in the casting with low
volume to surface area will solidify faster than sections with higher volume to
surface area. When manufacturing a part by metalcasting consideration of the of
V/A ratios is critical in avoiding premature solidification of the casting and the
formation of vacancies.

Source: http://thelibraryofmanufacturing.com/metalcasting_troubleshooting.html
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting Design Rules

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Design Rules

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Design Rules

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose
Casting processes, and their advantages and limitations
PROCESS ADVANTAGES LIMITATIONS
Sand Almost any metal is cast; no limit to Some finishing required; somewhat coarse finishl
size, shape or weight; low tooling wide tolerances.
cost.
Shell mould Good dimensional accuracy and Part size limited; expensive patterns and
surface finish; high production rate. equipment required.
Expendable pattern Most metals cast with no limit to Patterns have low strength and can be costly for
size; complex shapes low quantities.
Plaster mould Intricate shapes; good dimensional Limited to nonferrous metals; limited size and
accuracy and finish; low porosity. volume of production; mould making time
relatively long.
Ceramic mould Intricate shapes; close tolerance Limited size.
parts; good surface finish.
Investment Intricate shapes; excellent surface Part size limited; expensive patterns, moulds, and
finish and accuracy; almost any labor.
metal cast.
Permanent mould Good surface finish and High mould cost; limited shape and intricacy; not
dimensional accuracy; low porosity; suitable for high-melting-point metals.
high production rate.
Die Excellent dimensional accuracy and Die cost is high; part size limited; usually limited
surface finish; high production rate. to nonferrous metals; long lead time.
Centrifugal Large cylindrical parts with good Equipment is expensive; part shape limited.
quality; high production rate.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Casting Process Comparison

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

General Characteristics of Casting
Sand Shell Evaporative Plaster Investment Permanent Die Centrifugal
pattern mould
Typical materials cast All All All Nonferrous All All Nonferrous All
(Al, Mg, (Al, Mg, Zn,
Zn, Cu) Cu)

Weight (kg):
minimum 0.01 0.01 0.01 0.01 0.001 0.1 <0.01 0.01
maximum No limit 100+ 100+ 50+ 100+ 300 50 5000+
Typ. surface finish (µm Ra) 5-25 1-3 5-25 1-2 0.3-2 2-6 1-2 2-10
Porosity1 3-5 4-5 3-5 4-5 5 2-3 1-3 1-2
Shape complexity1 1-2 2-3 1-2 1-2 1 2-3 3-4 3-4
Dimensional accuracy1 3 2 3 2 1 1 1 3
Section thickness (mm):
minimum 3 2 2 1 1 2 0.5 2
maximum No limit - - - 75 50 12 100
Typ. dimensional tolerance 1.6-4 mm ±0.00 ±0.005- ±0.005 ±0.015 ±0.001-0.005 0.015
(mm/mm) (0.25 mm 3 0.010
for small)
Cost1,2
Equipment 3-5 3 2-3 3-5 3-5 2 1 1
Pattern/die 3-5 2-3 2-3 3-5 2-3 2 1 1
Labor 1-3 3 3 1-2 1-2 3 5 5
Typical lead time2,3 Days Week Weeks Days Weeks Weeks Weeks- Months
s months
Typical production rate2,3 1-20 5-50 1-20 1-10 1-1000 5-50 2-200 1-1000
(parts/mould-hour)
Minimum quantity2,3 1 100 500 10 10 1000 10,000 10-10,000

Notes: 1. Relative rating, 1 best, 5 worst. For example, die casting has relatively low porosity, mid- to low shape complexity, high dimensional accuracy,
high equipment and die costs and low labor costs. These ratings are only general; significant variations can occur depending on the manufacturing methods used.
2. Data taken from Schey, J.A., Introduction to Manufacturing Processes, 3rd ed, 2000.
3. Approximate values without the use of rapid prototyping technologies.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

Typical applications and characteristics for castings
TYPE OF ALLOY APPLICATION CASTABILITY* WELDABILITY* MACHIN‐ABILITY*
Aluminum Pistons, clutch housings, intake G‐E F G‐E
manifolds, engine blocks, heads, cross
members, valve bodies, oil pans,
suspension components
Copper Pumps, valves, gear blanks, marine F‐G F G‐E
propellers
Gray Iron Engine blocks, gears, brake disks and E D G
drums, machine bases
Magnesium Crankcase, transmission housings, G‐E G E
portable computer housings, toys
Malleable iron Farm and construction machiner, G D G
heavy‐duty bearings, railroad rolling
stock
Nickel Gas turbine blades, pump and valve F F F
components for chemical plants
Nodular iron Crankshafts, heavy‐duty gears G D G
Steel (carbon and Die blocks, heavy‐duty gear blanks, F E F‐G
low alloy) aircraft undercarriage members,
railroad wheels
Steel (high alloy) Gas turbine housings, pump and valve F E F
components, rock crusher jaws
White iron (Fe3C) Mill liners, shot blasting nozzles, G VP VP
railroad brake shoes, crushers and
pulverizers
Zinc Door handles, radiator grills E D E
*E, excellent; G, good; F, fair; VP, very poor; D, difficult.

Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose

References
1. Serope Kalpakjian and Steven Schmidt, Manufacturing Processes for Engineering
Materials, Pearson Education, 6th Edition
2. Mikell P. Groover, Fundamentals of Modern Manufacturing: Material. Processes, and
systems, 2nd Edition, Wiley India, 2007
3. P.N. Rao, Manufacturing Technology, Foundry, Forming and Welding, McGraw Hill
4. Hajra Choudhury, Elements of Workshop Technology–Vol.-II, Media Promoters and
Publishers
5. DeGarmo, E. P., J. T. Black, and R. A. Kohser, Materials and processes in
Manufacturing, PHI.
6. Amstead, B. H., P. F. Ostwald, and M. L. Begeman, Manufacturing Processes, 8th ed.,
Wiley, New York, 1988.
7. Schey, J. A., Introduction to Manufacturing Processes, McGraw-Hill, New York, 1977.
8. Lindberg, R. A., Processes and Materials of Manufacture,
9. O W Boston, Metal Processing, 2nd edition 1951, John Wiley and Sons
10. B. S. Raghuwanshi, A course in Workshop Technology- Dhanpat Rai & Sons.
11. Lecture notes of Professor J. Jeswiet, Mechanical Engg. Dept., Queen’s University,
Ontario, Canada
12. Lecture notes on ME 6222: Manufacturing Processes and Systems of Prof. J.S. Colton,
Georgia Institute of Technology
13. Lecture notes on Design & Manufacturing of Prof. S. Kim
14. Lecture notes on ME505/MFS505 Modeling of Manufacturing Processes & Machines of
Prof. I. S. Jawahir, Department of Mechanical Engineering, University of Kentucky
Lecture notes on PE204 Manufacturing Processes I, Joyjeet Ghose