Manufacturing processes.( SEMESTER + GATE )

 1. Manufacturing process:-

It is a process of converting raw material into a finished product by various processes , machines and energy.

it is a processes of value addition to the raw material.

* Classification:

(i)  Casting processes

(II) forming processes

(iii) fabrication processes

(iv) material removal processes

                        

a.  zero processes

 b. additive processes

  c. subtracting processes

(i) Casting Processes:-

In casting metals or alloy are initially heated to melt them .the molten metal is then poured into a mold cavity . where it is allowed to solidify. after solidification the product is taken out of the mold cavity and subjected to finishing operation as per requirement.

*Advantages:-

i. complex shape of the object can be produced.

ii. it is simple and less expensive process.

iii. Ductile and brittle material can be produced.

iv. Large size object can be produced by casting only.

* Limitation:-

i. casting object are not having smooth surface finish.

ii. It is laborious and time consuming processes.

iii. There is a possibility of gas defect can be expected in casting.

iv. mechanical properties of casting not having uniform properties due to non uniform cooling.

* Selection of manufacturing processes depends upon:-

i. Shape and size of object to produced.

ii. properties required by the object.

iii. Accuracy and surface finish required by the object.

iv. No. of component to be produced.

* Casting terminology:-

i. Pattern

ii. Flask

iii. Mould

iv. Gating system

v. Core

vi. Core prints

vii. Chaplet

viii. Chills

ix. Riser

* Pattern and pattern allowances:-

Pattern:-

It is replica of final casting to be produced with some modification.

The main modification are:

i. The addition of pattern allowances.

ii. the provision of core prints.

Pattern allowances:-

The dimensions of the pattern are different from the final dimension of the casting required this is known as pattern allowances.

* Classification of pattern allowances:-

i. Shrinkage or contraction

ii Draft or tapper

iii Machining or finish

iv Shake or rapping

v Distortion

i. Shrinkage (or) contraction allowances:-

When the liquid metal is allow to solidify there is a possibility of contraction of material during solidification process. due to this size of casting decrease.

The overall contraction of the casting take place in three stages:-

a. Contraction of liquid when its temperature changes from pouring temperature to freezing temperature

(Liquid shrinkage).

b. Contraction due to phase change from liquid to solid at freezing temperature.

c. Contraction of solid from freezing temperature to room temperature ( solid shrinkage).

Note:-

it is to be noted that first two stages of shrinkage are compensated by riser 

   and last stage i.e, solid shrinkage is compensated by providing allowances over the pattern.