IIT Bombay Notes | EduRev

Mechanical Engineering : IIT Bombay Notes | EduRev

 Page 1


IIT Bombay 
 
 
 
 
 
 
 
 
Module 
3 
Selection of Manufacturing 
Processes 
Page 2


IIT Bombay 
 
 
 
 
 
 
 
 
Module 
3 
Selection of Manufacturing 
Processes 
IIT Bombay 
 
 
 
 
 
 
 
 
Lecture 
3 
Design for Bulk Deformation 
Processes 
Page 3


IIT Bombay 
 
 
 
 
 
 
 
 
Module 
3 
Selection of Manufacturing 
Processes 
IIT Bombay 
 
 
 
 
 
 
 
 
Lecture 
3 
Design for Bulk Deformation 
Processes 
IIT Bombay 
Instructional objectives 
By the end of this lecture, the students are expected to learn the working principle of bulk 
deformation processes and the factors to be considered in the selection and design of a bulk 
deformation process. Furthermore, how careful design can improve the quality of the final 
product is also highlighted. 
 
What is Bulk Deformation? 
Metal forming operations which cause significant shape change by plastic deformation in 
metallic parts are referred to bulk deformation processes. In most of the cases cylindrical bars 
and billets, rectangular billets and slabs, and similar shapes are the initial shapes which are 
plastically deformed in cold, warm or hot conditions into a desired shape. Complex shapes 
with good mechanical properties can be produced by bulk deformation processes. Following 
metal forming operations are commonly referred to as bulk deformation processes. 
1. Forging – The initial shape is squeezed and shaped between two opposing dies. 
2. Rolling – A slab or plate is squeezed between two rotating rolls to reduce the height 
so as to produce thinner shapes like sheets, 
3. Extrusion – The initial shape is squeezed through a shaped die such that the cross-
section of the deformed part becomes similar to that of the die opening. 
4. Wire and bar drawing – The diameter of typical cylindrical bars or wires is reduced 
by pulling it through a shaped die. 
 
Forging 
Forging is the process by which a metallic part is deformed to a final shape with the 
application of pressure and with or without the application of heat. Forging processes can 
broadly be classified as follows. 
Open Die Forging 
The workpiece is compressed between two flat dies facilitating lateral flow of material 
without constraint, 
Impression Die Forging 
The workpiece is compressed between two dies with a cavity or impression that is imparted 
to the workpiece. The metal flow is constrained within the impression of the dies. However, 
the excess material remains as flash.  
Page 4


IIT Bombay 
 
 
 
 
 
 
 
 
Module 
3 
Selection of Manufacturing 
Processes 
IIT Bombay 
 
 
 
 
 
 
 
 
Lecture 
3 
Design for Bulk Deformation 
Processes 
IIT Bombay 
Instructional objectives 
By the end of this lecture, the students are expected to learn the working principle of bulk 
deformation processes and the factors to be considered in the selection and design of a bulk 
deformation process. Furthermore, how careful design can improve the quality of the final 
product is also highlighted. 
 
What is Bulk Deformation? 
Metal forming operations which cause significant shape change by plastic deformation in 
metallic parts are referred to bulk deformation processes. In most of the cases cylindrical bars 
and billets, rectangular billets and slabs, and similar shapes are the initial shapes which are 
plastically deformed in cold, warm or hot conditions into a desired shape. Complex shapes 
with good mechanical properties can be produced by bulk deformation processes. Following 
metal forming operations are commonly referred to as bulk deformation processes. 
1. Forging – The initial shape is squeezed and shaped between two opposing dies. 
2. Rolling – A slab or plate is squeezed between two rotating rolls to reduce the height 
so as to produce thinner shapes like sheets, 
3. Extrusion – The initial shape is squeezed through a shaped die such that the cross-
section of the deformed part becomes similar to that of the die opening. 
4. Wire and bar drawing – The diameter of typical cylindrical bars or wires is reduced 
by pulling it through a shaped die. 
 
Forging 
Forging is the process by which a metallic part is deformed to a final shape with the 
application of pressure and with or without the application of heat. Forging processes can 
broadly be classified as follows. 
Open Die Forging 
The workpiece is compressed between two flat dies facilitating lateral flow of material 
without constraint, 
Impression Die Forging 
The workpiece is compressed between two dies with a cavity or impression that is imparted 
to the workpiece. The metal flow is constrained within the impression of the dies. However, 
the excess material remains as flash.  
IIT Bombay 
Flashless Forging 
This is an improved version of Impression-die forging process. The initial volume of the 
workpiece is carefully taken so that no excess flash is produced.  
 
Figure 3.3.1 outlines the schematic set-up for the above three forging processes. Following 
are some of the major advantages of forging processes. 
(1) It improves the structure as well as mechanical properties of the metallic parts. 
(2) Forging facilitates orientation of grains in a desired direction to improve the 
mechanical properties. 
(3) Forged parts are consistent in shape with the minimum presence of voids and 
porosities. 
(4) Forging can produce parts with high strength to weight ratio. 
(5) Forging processes are very economical for moderate to high volume productions. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 3.3.1 Schematic presentations of (a) open-die forging, (b) impression-die forging, 
 and (c) flashless forging 
Page 5


IIT Bombay 
 
 
 
 
 
 
 
 
Module 
3 
Selection of Manufacturing 
Processes 
IIT Bombay 
 
 
 
 
 
 
 
 
Lecture 
3 
Design for Bulk Deformation 
Processes 
IIT Bombay 
Instructional objectives 
By the end of this lecture, the students are expected to learn the working principle of bulk 
deformation processes and the factors to be considered in the selection and design of a bulk 
deformation process. Furthermore, how careful design can improve the quality of the final 
product is also highlighted. 
 
What is Bulk Deformation? 
Metal forming operations which cause significant shape change by plastic deformation in 
metallic parts are referred to bulk deformation processes. In most of the cases cylindrical bars 
and billets, rectangular billets and slabs, and similar shapes are the initial shapes which are 
plastically deformed in cold, warm or hot conditions into a desired shape. Complex shapes 
with good mechanical properties can be produced by bulk deformation processes. Following 
metal forming operations are commonly referred to as bulk deformation processes. 
1. Forging – The initial shape is squeezed and shaped between two opposing dies. 
2. Rolling – A slab or plate is squeezed between two rotating rolls to reduce the height 
so as to produce thinner shapes like sheets, 
3. Extrusion – The initial shape is squeezed through a shaped die such that the cross-
section of the deformed part becomes similar to that of the die opening. 
4. Wire and bar drawing – The diameter of typical cylindrical bars or wires is reduced 
by pulling it through a shaped die. 
 
Forging 
Forging is the process by which a metallic part is deformed to a final shape with the 
application of pressure and with or without the application of heat. Forging processes can 
broadly be classified as follows. 
Open Die Forging 
The workpiece is compressed between two flat dies facilitating lateral flow of material 
without constraint, 
Impression Die Forging 
The workpiece is compressed between two dies with a cavity or impression that is imparted 
to the workpiece. The metal flow is constrained within the impression of the dies. However, 
the excess material remains as flash.  
IIT Bombay 
Flashless Forging 
This is an improved version of Impression-die forging process. The initial volume of the 
workpiece is carefully taken so that no excess flash is produced.  
 
Figure 3.3.1 outlines the schematic set-up for the above three forging processes. Following 
are some of the major advantages of forging processes. 
(1) It improves the structure as well as mechanical properties of the metallic parts. 
(2) Forging facilitates orientation of grains in a desired direction to improve the 
mechanical properties. 
(3) Forged parts are consistent in shape with the minimum presence of voids and 
porosities. 
(4) Forging can produce parts with high strength to weight ratio. 
(5) Forging processes are very economical for moderate to high volume productions. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 3.3.1 Schematic presentations of (a) open-die forging, (b) impression-die forging, 
 and (c) flashless forging 
IIT Bombay 
Defects in Forging 
Though forging process provides good quality products compared to other manufacturing 
processes, some defects that are lightly to come if proper care is not taken in forging process 
design. A brief description of such defects and their remedial method is given below. 
Unfilled Section 
This defect refers to localized unfilled portion within the die cavity due to improper design of 
the forging die or inappropriate selection of the forging technique. 
Cold Shut 
Cold shut appears as small cracks at the corners of the forged part that is caused primarily 
due to very tight fillet radii that inhibit smooth material flow towards the corner of the die. 
Scale Pits 
Scale pits are seen as irregular deputations on the surface of the forging that is caused 
primarily due to improper cleaning of the stock used for forging. The oxide and scale gets 
embedded into the finish forging surface. When the forging is cleaned by pickling, these are 
seen as deputations on the forging surface. 
Die Shift 
Die shift is caused by the misalignment of the top and the bottom dies making the two halves 
of the forging to be improper shape. 
Flakes 
These are basically internal ruptures caused by the improper cooling of the large forging. 
Rapid cooling causes the exterior to cool quickly causing internal fractures. This can be 
remedied by following proper cooling practices. 
Improper Grain Flow 
This is primarily caused by the improper design of the die that induces material flow in an 
inappropriate manner leading to various defects. 
 
Rolling 
Rolling is a forming operation where cylindrical rolls are used to reduce the cross sectional 
area of a bar or plate with a corresponding increase in the length. Rolling process is widely 
used because of high productivity. Figure 3.3.2 depicts schematic set-up of rolling process. 
Rolling processes are broadly classified by the geometry of the final rolled shape of the 
workpiece material such as flat rolling that is used to reduce thickness of a rectangular 
Read More
Offer running on EduRev: Apply code STAYHOME200 to get INR 200 off on our premium plan EduRev Infinity!

Related Searches

Important questions

,

Free

,

Sample Paper

,

IIT Bombay Notes | EduRev

,

Summary

,

study material

,

ppt

,

video lectures

,

Semester Notes

,

practice quizzes

,

Viva Questions

,

shortcuts and tricks

,

IIT Bombay Notes | EduRev

,

Previous Year Questions with Solutions

,

Extra Questions

,

Exam

,

pdf

,

MCQs

,

Objective type Questions

,

IIT Bombay Notes | EduRev

,

past year papers

,

mock tests for examination

;