3. Forming operation
Forming process make use of suitable stresses like
compression, tension, shear or combined stresses to
cause plastic deformation of the materials to produce
required shapes. In forming, no material is removed
i.e. they are deformed
4. Some of the forming processes
are:
Forging
Extrusion
Rolling
Drawing
5. Forging process
Forging is a manufacturing
process involving the shaping of metal
using localized compressive forces.
7. Introduction
A metal is shaped by compressive forces
Oldest metal working process – 4000BC
Can be performed with a hammer and anvil
Typical forged products:
Bolts
Rivets
Connecting rods
Gears
8. Lading-gear components for
the C5A and C5B transport
aircraft, made by forging.
Steps involved in forging a bevel
gear with a shaft.
9. Grain Structure
Parts have good strength
High toughness
Forgings require additional heat treating
Fig : A part made by three different procedures, showing grain flow (a) casting (b) machining (c) forging
10. Open-Die Forging
Is the simplest forging process
Sizes can very from very small parts to very large parts
11. Impression-Die & Closed-Die Forging
The workpiece acquires the shape of the die cavities while
being forged between the two shaped dies
12. Precision Forging
Used for economic reasons
The part formed is close to the final dimensions
Less machining is needed
Higher capacity equipment is needed
Aluminum and Magnesium alloys work well in the process
14. Extrusion process
Extrusion is a
manufacturing process used
to create objects of a fixed
cross-sectional profile. A
material is pushed or drawn
through a die.
18. Drawing process
Drawing is a metal
working process which uses
tensile forces to stretch
metal. ...Cold drawing is
primarily used
in manufacturing plastic .
20. Sheet metal
The success of forming is in relation to two
things, the flow and stretch of material. As
a die forms a shape from a flat sheet of
metal, there is a need for the material to
move into the shape of the die. The flow of
material is controlled through pressure
applied to the blank and lubrication applied
to the die or the blank. If the form moves
too easily, wrinkles will occur in the part.
To correct this, more pressure or less
lubrication is applied to the blank to limit
the flow of material and cause the material
to stretch or thin. If too much pressure is
applied, the part will become too thin and
break. Drawing metal is the science of
finding the correct balance between
wrinkles and breaking to achieve a
successful part.
21. Deep drawing
Main article: Deep drawing
Sheet metal drawing becomes deep
drawing when the workpiece is drawing
longer than its diameter. It is common that
the workpiece is also processed using
other forming processes, such
as piercing, ironing, necking, rolling,
and beading.
22. Bar, tube & wire
Bar, tube, and wire drawing all work upon
the same principle: the starting stock
drawn through a die to reduce the
diameter and increase the length. Usually
the die is mounted on a draw bench. The
end of the workpiece is reduced or pointed
to get the end through the die. The end is
then placed in grips and the rest of the
workpiece is pulled through the
die.[1] Steels, copper alloys, and aluminium
alloys are common materials that are
drawn.[3]
Drawing can also be used to produce a
cold formed shaped cross-section. Cold
drawn cross-sections are more precise and
have a better surface finish than hot
extruded parts. Inexpensive materials can
be used instead of expensive alloys for
strength requirements, due to work
hardening.[4]
23. Plastic drawing
Plastic drawing, sometimes referred to as cold drawing, is the
same process as used on metal bars, but applied to plastics.[6]
Cold drawing is primarily used in manufacturing plastic fibers.
The process was discovered by Julian Hill in 1930 while trying to
make fibers from an early polyester.[7] It is performed after the
material has been "spun" into filaments; by extruding the
polymer melt through pores of a spinneret. During this process,
the individual polymer chains tend to somewhat align because
of viscous flow. These filaments still have
an amorphous structure, so they are drawn to align the fibers
further, thus increasing crystallinity, tensile
strength and stiffness. This is done on a draw
twister machine.[7][8]
For nylon, the fiber is stretched four times its spun length. The
crystals formed during drawing are held together by hydrogen
bonds between the amide hydrogens of one chain and
the carbonyl oxygens of another chain.
