Systematic procedures can be developed for the selection of primary process/material combinations

1. Primary Process/Material
Selection
SRIVARDHAN VUTTARADI
M.TECH (AMS)

2. Primary Process/Material Selection
• Systematic procedures can be developed for the selection
of primary process/material combinations.
• Such procedures operate by eliminating processes and
materials as a more detailed specification of the required
part’s attributes occurs.

3. Figure : Oven bracket part.
The elements of such a selection procedure can be
illustrated by considering, as an example
the part shown in Figure, which is to be used as an oven
bracket.

5. • This part is specified as follows.
Shape Attributes
1. Depressions……………………………. Yes
2. Uniform wall…………………………… Yes
3. Uniform cross-section ……………. Yes
4. Axis of rotation ………………………. No
5. Regular cross-section……………… No
6. Captured cavity ……………………… No
7. Enclosed cavity……………………….. No
8. No draft …………………………………. Yes
Material Requirements
1. Maximum temperature of 500°C
2. Excellent corrosion resistance to weak acids and alkalis

6. The example has been used previously by Wilson et al.
[17,18] and is used again here as an illustrative example.
In terms of the shape-producing capabilities listed in
Table 2.2, this part is specified as follows.
In this list,
the shape attributes with a “Yes” eliminate those processes
that are not capable of producing these features.
Those features with a “No” eliminate those processes that are
only capable to producing parts with these features present.

8. Applying these requirements progressively to the basic process/material
compatibility matrix shown in Figure A produces the results.

9. Method of approach
1.the shape-producing capabilities
2.compatibility matrix
1. based on four geometric attributes
2. based on further four attributes
3. Final process selection based on geometric
attributes
4. Final selection based on process/material
combinations

10. Process elimination based on four geometric attributes of the part in
Figure
1. Depression ........................ Yes
2. Uniform wall ..................... Yes
3. Uniform cross section ..... Yes
4. Axis of rotation ................. No

12. Process elimination based on further four attributes of the part in
Figure
5. Regular cross section ....... No
6. Captured cavity ............... No
7. Enclosed cavity ................ No
8. Draft free ......................... Yes

14. Final process selection based on geometric attributes of the part in
Figure

16. Final selection based on process/material combinations
of the part shown in Figure

18. • Figure 2.9 shows the processes eliminated by the first four
shape attributes listed above
• and Figure 2.10 shows the processes eliminated by the
other four shape attributes.
• Combining these together results in four selected processes
(Figure 2.11):
powder metal parts,
hot extrusion, machining from stock, and
wire electric discharge machining (EDM).

19. • Finally, imposing the material requirements results in the
final selection of processes and materials shown in Figure
2.12.
• These selected combinations can then be ranked by other
criteria, such as estimates of manufacturing costs.
• In this example, wire EDM would clearly not be an economic
choice.
• The wire electrode spark erosion process involves very long
cycle times and is used principally in tool and die making.

20. • It is only used in part production for small batches of wafer
thin parts, which can be cut in multiples from stacks of
blanks, or for very small batches of complex uniform cross-
section parts.
• This leaves only three processes available to carry out the
primary processing.
• If these processes were deemed not to be acceptable
choices, then the alternatives would be to make changes to
some of the shape attributes, or allocate one or more of the
attributes to secondary processes.
• If, for example, we allow slight tapered upper and lower
surfaces in the 20 mm wide depression of the oven bracket,
we would enable both sand casting and investment casting
as potential processes.

21. REFERENCE BOOKS:
• Product design for Manufacture and Assembly, Geoffrey
Boothroyd,Marcel Dekker Inc. NY, 1994.

22. Thank you