First Year Engineering Basic Mechanical Engineering

1. Unit No. – 5
Manufacturing Processes

3. Highly economical process, so cost of component produced is
low.
No high initial investment.
No highly skilled manpower required.
Suitable for small quantity batch production as well as mass
production.

4. The components produced by sand casting process have poor
dimensional accuracy as well as poor surface finish. Hence not
suitable for precision work.
Not suitable for components of highly intricate shape.
It cannot produce extremely thin sections.
Each casting requires one mould. Hence, this process requires
large man power for mould making.
Used for making gear-box housing, machine tool beds, gears,
bearing housing, machine tool frames.

6. The molten metal under high
pressure of 10-210 MPa is
injected into permanent
mould called die.

7. Gives high dimensional accuracy and good surface finish.
It can eliminate the requirements of machining and finishing
operations.
Suitable for components with highly intricate shapes.
It can produce extremely thin section.
The process permits repeated use of mould (upto 25000 times).
The rate of production is high and requires less space.

8. Due to high initial cost of moulds and equipment , it is
economical for mass production only.
Due to metallic moulds it is not suitable for high melting point
metals such as ferrous alloys.
The process is not suitable for large size castings.
Aluminium pistons, cylinder block, gear blanks, kitchenwares,
etc.

9. It is the process in which the component of
desired shape and size is obtained through the plastic
deformation of the metal or alloy under the action of
externally applied force.
It can be carried out on the metal in either hot or cold
condition.
The various metal forming processes are:
The external force on the metal during the metal forming may
be tensile force, compressive force, shear force or a
combination of these forces.

10. Forging is a metal forming process in which the metal or
alloy is first heated and then plastically deformed to the
desired size and shape by the application of compressive force
using a hand hammer, a power hammer, or a press.
The material is heated to a temperature at which its elastic
properties completely disappear. This temperature is known
as forging temperature and it varies from material to material.
At forging temperature, the material becomes soft and obeys
the law of plastic flow. It thus deforms plastically in the
direction of least resistance without fracture.

11. The material is deformed into the desired
shape between two parts called dies. The
shape of the die matches with the shape
of desired component.
The forging press consist of lower die
fixed to the frame while upper die is
connected to ram.
The hot material is kept on the lower die.
During the downward stroke of the ram,
the upper die exerts the sudden
compressive force on the hot material and
is converted into desired shape.
The press operates at about 30 - 60 strokes/min.

12. The material used for forging should be ductile as ductility
enables the material to deform plastically with out fracture.
Common examples are: Low & medium carbon steel, alloy steel,
stainless steels, copper alloys, aluminium alloys, etc.
High dimensional accuracy & surface finish. Hence it
eliminates other machining & finishing operations.
Forging reduces grain size which results in improving strength
and toughness.
Forged products have high strength to weight ratio.

13. Brittle materials like cast iron cannot be forged.
Cannot produce complex intricate shape like casting process.
Cost of forged components is more than casted components.
Cost of forging dies is high.
IC engine parts like crankshaft, connecting rods, rocker arm, etc.
Small tools like spanners, etc.
Levers,
Automobile and aircraft components.

15. The material or work piece is
deformed between two flat dies
or dies of very simple shape.

16. The material or work piece is
deformed between two dies
which have impression of desired
shape.

17. Hand forging is the
process of
deforming the hot
workpiece into
desired shape by
applying repeated
blows of hand held
hammer.

18. The initial cost of hand forging setup is low.
The cost of components produced by hand forging is low.
The quality of forging is dependent on the skill of the operator.
Used for making small components of simple shape.
Since the rate of production is low it is not suitable for mass
production.

19. The workpiece is deformed into
desired shape by raising the die
and allowing it to fall so as to
impart the blow or impact on
the material.
The impact force is proportional
to the combined weight of the
ram and upper die and the
stroke of the ram.

20. The quality of forging is consistent and good.
Medium sized components can be forged.
Suitable for mass production because rate of production is high.
The initial cost of drop forging process is high.
The process generates lot of noise.

21. The workpiece is deformed into desired
shape by slow squeezing action.
The gradual motion of the upper die
transfers the compressive force uniformly
and gradually to the hot material so as to
deform it to the desired shape.
The compressive force is proportional to
the cross-sectional area of the cylinder
and the pressure of the hydraulic fluid.

22. It is faster as only one squeeze is needed per component.
As the force is transferred uniformly & gradually to the hot
material it results in uniform material properties.
Large sized components (upto 125 kg & 3 m long) can be forged.
The operation is quieter than drop forging process.
The initial cost of setup is high.
The running cost of press forging process is high.

23. The cross-section of workpiece is increased locally with a
corresponding reduction in its length by slow squeezing action.
Apart from the direction of operation (i.e. horizontal direction),
the process is similar to press forging.