Molding & Its types

Injection Molding
Rotational Molding
Blow Molding
Compression Molding
Extrusion Molding
Transfer Molding

 Molding or moulding is the process of manufacturing by

Its

shaping pliable raw material using a rigid frame or model

called a pattern.
Molding technology has brought revolution in our daily
life. With the passage of time it became modern and more
efficient and effectively
Its applications are in the ,automotive industries; it is
used in plumbing industry, construction industry, and aero
space industries
Its products are plastic bottles, water tanks, pipes, toys,
bags and many more.
major fields are
Injection molding
Compression molding
Rotational molding
Blow molding
Transfer molding
Extrusion molding

DEFINITION

Injection molding is a process whereby a solid thermoplastic material is heated

until it reaches a state of fluidity , is then transferred under pressure(injected) into
a closed hollow space

(mold cavity), and then cooled in the mold till it again reaches a solid state,
conforming in shape to the mold cavity.

HISTORY
John Hyatt patented the first injection molder in 1872. . In 1951, William H. Willert
invented the first molder machine to use a screw to provide continuous feed of liquid
material.
From the 1980s on, the most significant
developments in injection molding have been
in the area of computerization of the process.

John Hyatt

William Willert
Injection molding

machine

 Apparatus description
Injection molding machines consist of a material
hopper, an injection ram or screw-type plunger, and a

heating unit and cooling system. presses hold

the molds in which the components are shaped.

Two types of operating systems

1.

Reciprocating Screw System

Schematic of injection molding machine

Plastic is melted through shearing and external

heat, forced into the mold with a the screw.

2. Ram Injection Molding

Plastic is pre-melted in the hopper, fed into a chamber,
and forced into the mold with a piston.

Melting
The process usually begins with taking the polymers in the
form of pellets or granules and then Material is fed into a
heated barrel, where it melted

Injecting resin

In the injecting process the screw type plunger moves

with the help of external rotating rods, and the
heating system heats the granules.
Part cooling

In the part cooling step the screw in the plunger moves

the material to the mold part which is the cooling part
where it is cooled and
hardens to the configuration of the mold cavity.

part ejection

In part ejection The mold is then opened and the part is

ejected.

 Injection molding is used to create milk

cartons, packaging.
Bottle caps, automotive dashboards, pocket

combs, toys and many plastic products

It is used in plumbing industry and

construction industry
It is used in automotive industry
It is used in aero space industry

 Advantages
Injection molding is the

most common method of

part manufacturing. It is
ideal for producing high
volumes of the same
object
Low costs in mass
production, low labour
cost, minimal scrap losses
High precision
It has ability of using wide

range of materials
Little need to finish parts
after molding

Disadvantages
High initial setup costs
High initial cost-mold,

Injection
machine, Auxiliary
equipment
High amount of scrap

DEFINITION
Rotational molding, also

known as rotomolding, is a
molding process for creating
many kinds of mostly hollow
items, typically of plastic.

Process description
Rotational molding is a 4 stage

process that includes adding

material, heating, cooling, and
demolding

 Loading a measured quantity

of polymer (usually in powder

form) into the mold.

Heating the mold in an

oven while it rotates, until all the

polymer has melted and
adhered to the mold wall

 Cooling the mold, usually by

fan. This stage of the cycle can

be quite lengthy. The polymer
must be cooled so that it
solidifies and can be handled
safely by the operator. The
part will shrink on cooling,
coming away from the mold,
and facilitating easy removal
of the part
Mold is moved to the open

station where part is removed

 Roto-moulded traffic cones

with
Reflective sleeve for night
visibility.
Rotational molding of plaster is
used to produce hollow
statuettes.
Chocolate is rotationally
molded to form hollow treats
Industrial products like Tanks,
containers, housing
Consumer products like Desks,
beds, dog house
Footballs, helmets.
Recreational products like Toys,
pools, balls
Agricultural products like
Troughs, tractor cabs

 Advantages

Disadvantages

Low molding pressure allows

Surface details limited to

use of light-duty molds

Manufacturing large, hollow
parts such as oil tanks is
much easier by rotational
molding than any other
method
Molds can quickly be built
and put into production
Mold cavity is the only thing
in contact with the material
No scrap: material that goes
in comes out as finished part

outside surface-hollow
mold
Mold is heated and cooled
as well as plastic
Long cycle times and high
heat
Maintaining precise
dimensions is difficult

 Definition
Blow molding, also known as blow

forming, is a manufacturing process

by which hollow plastic parts are
formed. It is a process used to
produce hollow objects from
thermoplastic.

History

The process of using air to blow hot

material was first used by the
Syrians, who realized that a glass
bulb on the end of a blow pipe
could be shaped into many useful
hollow forms,. William Kopitke were
the first verified person
who used the Blow Molding Process. In
1938, Ferngren and Kopitke
produced a blow molding machine .
In 1970, Coca-Cola test markets the
worlds first plastic carbonated
beverage bottle.

 The blow molding process

begins with melting down the
plastic and forming it into a
parison or preform. The parison
is a tube-like piece of plastic
with a hole in one end in which
compressed air can pass
through.
A pressurized gas, usually air,

is used to expand the hot

preform and press it against a
mold cavity. The pressure is
held until the plastic cools.
Once the plastic has cooled

and hardened the mold opens

up and the part is ejected

 Toy wheels, automobile seat

back, fuel tanks, flower pots,

automobile bumpers, cabinet
panels .
Milk bottles, Pharmaceutical

bottles, Antifreeze bottles,

Polypropylene bottles
Garbage cans

Advantages

Disadvantages

Advantages of blow molding

include:
low tool and die cost
Fast production rates
Ability to mold complex part
Produces recyclable parts.
Increase the materials tensile
Strength, barrier properties,
clarity.
Blow molding produces a
container from less raw
material and with improved
economics properties.

Disadvantages of blow
molding include:
limited to hollow parts
wall thickness is hard to
control.

DEFINITION
The process of molding a
material in a confined shape
by applying pressure and
usually heat Almost exclusively
for thermoset materials. It is
used to produce mainly
electrical products
.

1.

Molding compound is placed

in an open, heated mold
cavity.

2.

The mold is closed and

pressure is then applied to
force the material to fill up
the entire mold cavity.
Excess material is channelled
away by the overflow
grooves. The heat and
pressure are maintained until
the plastic material is cured.

3.

The final part after the mold

Is removed

 This process is commonly

used for manufacturing

electrical parts
It is also used for
manufacturing dinnerware
and type of products
It is also used for
manufacturing gears, cams
This process is used to
produce buttons, buckles,
knobs, handles,
Appliance housing, radio
cases, and large containers.

Advantages

Disadvantages

Low initial setup costs

Production speed is not up

Fast setup time

to injection molding
standards
Less-than-ideal product
consistency
It is not suitable for some
types of parts

Good surface finish (in

general)
Wastes relatively little
material

 Definition

Extrusion is a process used to

create objects of a fixed crosssectional profile. It is like
forcing of solid metal through
a suitably shaped orifice under
compressive forces.
Extrusion is somewhat
analogous to squeezing
toothpaste through a tube,
although some cold extrusion
processes more nearly
resemble forging, which also
deforms metals by application
of compressive forces. Most
metals can be extruded,
although the process may not
be economically feasible for
high-strength alloys.

 In this process, a heated billet

of metal is placed in a
cylindrical chamber and then
compressed by a hydraulically
operated ram .
The opposite end of the

cylinder contains a die having

an orifice of the desired shape;
as this die opening is the path
of least resistance for the billet
under pressure,
The metal, in effect, squirts

out of the opening as a

continuous bar having the
same cross-sectional shape as
the die opening.

 Extrusion has found great

application in food processing.

Products such as pastas,
breakfast cereals, French fries,
baby food, dry pet food and
ready-to-eat snacks are mostly
manufactured by extrusion
Chewing gums, drinking
straws, plumbing pipes, door
insulation seals, optical fibers,
and steel or aluminum I-beams.
A multitude of polymers are
used in the production of
plastic tubing, pipes, rods, rails,
seals, and sheets or films.
Many modern bricks are also
manufactured using a brick
extrusion process.

Advantages
Low initial setup costs
Fast setup time
Low production costs
Advantages of this process

over other manufacturing

processes are its ability to
create very complex crosssections and work materials
that are brittle, because the
material only encounters
compressive and shear
stresses.

Disadvantages
Moderate production speed
Mediocre precision
Limited to parts with a

uniform cross section

 Transfer molding process

beginning with the uncured

material placed in a transfer
plate located above the cavity
area, rather than being placed
directly in the cavity as in
compression molding
applications. heat is then
applied to the rubber and
transferred from the transfer
plat, being pushed through a
gate by a piston, into the
cavity where the material is
then vulcanized using heat and
pressure.

 Step #1 - A piece of uncured

material is placed into a

portion of the mold called the
"pot." The plunger (on the
top-most part of the mold)
fits snugly into the "pot.
Step #2 - The mold is

closed up and under

hydraulic pressure the
material is forced through
the small hole (the "gate")
into the cavity. The mold is
held closed while the
material cures.

 Step #3 - The plunger is

raised up and the "transfer

pad" material may be
removed and thrown away.
Step #4 - Mold is opened
and the part can be
removed. The flash and the
gate may need to be
trimmed.

 Some common products are

utensil handles, electric

appliance parts, electronic
component, and connectors.
Transfer molding is widely
used to enclose or
encapsulate items such as
coils, integrated circuits,
plugs, connectors, and other
components.
In the semiconductor
industry, package
encapsulation is usually
done with transfer molding
due to the high accuracy of
transfer molding tooling and
low cycle time of the
process.

Advantages

Disadvantages

Provides more product

The transfer pad is scrap

consistency than
compression molding
Cycle times are shorter
than compression molding
Better than compression
molding for rubber-to-metal

Cycle time is longer than

injection molding
Product consistency is
poorer than injection
molding