EXPERIMENT

MACHINING AND FORMING:

AIM: - To study constructional features of following machines through drawings/ sketches:

a. Grinding machines (Surface, Cylindrical)

b. HydraulicPress
c. Draw Bench

d. Drawing and ExtrusionDies

e. RollingMills

THEORY:
(1) Grindingmachine:

A grinding machine, often shortened to grinder, is a machine tool used for

grinding, which is a type of machining using an abrasive as the cutting Each grain of
abrasive on the wheel's surface cuts a small chip from the work piece via shear deformation.

Grinding is used to finish workpieces that must show high surface quality (e.g., low
surface roughness) and high accuracy of shape and dimension. As the accuracy in
dimensions in grinding is on the order of 0.000025 mm, in most applications it tends to be a
finishing operation and removes comparatively little metal, about 0.25 to 0.50 mm depth.
However, there are some roughing applications in which grinding removes more material.

Cylindrical grinder, which includes both the types that use center sand the center less
types. A cylindrical grinder may have multiple grinding wheels. The workpiece is rotated
and fed past the wheel(s) to form a cylinder. It is used to make precision rods, tubes, bearing
races, bushings, and many other parts.

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 Surface grinder which includes the wash grinder. A surface grinder has a "head"
which is lowered, and the work piece is moved back and forth past the grinding wheel on a
table that has a permanent magnet for use with magnetic stock. Surface grinders can be
manually operated or have CNC controls.

(2) Hydraulic press:

A hydraulic press is a machine (see machine press) using a hydraulic cylinder

to generate a compressive force.

The hydraulic press depends on Pascal's principle: the pressurethroughout a closed

system is constant. One part of the system is a piston acting as a pump, with a modest
mechanical force acting on a small cross-sectional area; the other part is a piston with a
larger area which generates a correspondingly large mechanical force. Only small-diameter
tubing(which more easily resists pressure) is needed if the pump is separated from the press
cylinder.
Pascal's law: Pressure on a confined fluid is transmitted undiminished and acts with
equal force on equal areas and at 90 degrees to the container wall. A fluid, such as oil, is
displaced when either piston is pushed inward. The small piston, for a given distance of
movement, displaces a smaller amount of volume than the large piston, which is proportional
to the ratio of areas of the heads of the pistons. Therefore, the small piston must be moved a
large distance to get the large piston to move significantly. The distance the large piston will
move is the distance that the small piston is moved divided by the ratio of the areas of the
heads of the pistons. This is how energy, in the form of workin this case, is conserved and
the Law of Conservation of Energy is satisfied. Work is force times distance, and since the
force is increased on the larger piston, the distance the force is applied over must be
decreased

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 (3) Drawbench

A Draw bench is a machine used to do work on a metal, such as changing the shape of the
metal without applying heat and applying only pressure.

Machine Construction

It consists of a chain drive, driven by a motor and a set of gears. The other end of the
machine consists of a die mounted on a thick steel plate. The workpiece is inserted through
the die and clamped on a trolley which then is hooked onto the chain for pulling across.

Die: The die is usually made of carbide with a steel housing. The die can be made to any
desired shape (round, square, rectangle, triangle, half round, L shape, oval etc.)

DRAWBENCH

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(4) Drawing Die:is a metal working process used to reduce the cross-sectionof a wire by
pulling the wire through a single, or series of, drawing die(s). There are many applications
for wire drawing, including electrical wiring, cables, tension-loaded structural components,
springs, paper clips, spokes for wheels, and stringed musical instruments. Although similar
in process, drawing is different from extrusion, because in drawing the wire is pulled, rather
than pushed, through the die. Drawing is usually performed at room temperature, thus
classified as a cold working process, but it may be performed at elevated temperatures for
large wires to reduce forces

DRAWING DIE

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(5) Rolling mills:

In metalworking, rolling is a metal forming process in which metal stock is passed through a
pair of rolls. Rolling is classified according to the temperature of the metal rolled. If the
temperature of the metal is above its recrystallization temperature, then the process is termed
as hot rolling. If the temperature of the metal is below its recrystallization temperature, the
process is termed as cold rolling. In terms of usage, hot rolling processes more tonnage than
any other manufacturing process, and cold rolling processes the most tonnage out of all cold
working processes.

There are many types of rolling processes, including ring rolling, roll bending, roll forming,
profile rolling, and controlled rolling.

TWO HIGH ROLLING MILL

A rolling mill, also known as a reduction mill or mill, has a common construction
independent of the specific type of rolling being performed:

Rolling mill for cold rolling metal sheet like this piece of brass sheet

Workrolls

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 Backup rolls - are intended to provide rigid support required by the working rolls to
prevent bending under the rolling load

Rolling balance system - to ensure that the upper work and back up rolls are maintain
in proper position relative to lower rolls
Roll changing devices - use of an overhead crane and a unit designed to attach to the
neck of the roll to be removed from or inserted into the mill.
Mill protection devices - to ensure that forces applied to the backup roll chocks are
not of such a magnitude to fracture the roll necks or damage the mill housing
Roll cooling and lubrication systems
Pinions - gears to divide power between the two spindles, rotating them at the same
speed but in different directions
Gearing - to establish desired rolling speed
Drive motors - rolling narrow foil product to thousands of horsepower
Electrical controls - constant and variable voltages applied to the motors

Coilers and uncoilers - to unroll and roll up coils of metal

Slabs are the feed material for hot strip mills or plate mills and blooms are rolled to billets in
a billet mill or large sections in a structural mill. The output from a strip mill is coiled and,
subsequently, used as the feed for a cold rolling mill or used directly by fabricators. Billets,
for re-rolling, are subsequently rolled in either a merchant, bar or rod mill. Merchant or bar
mills produce a variety of shaped products such as angles, channels, beams, rounds (long or
coiled) andhexagons.

Approved By: Prepared By:

HOD (Me Deptt.) Lab Incharge:

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