How is a processing route chosen?

The selection of a suitable process to manufacture a component is not a straightforward matter. There are many factors which need to be considered, for example: size of component, material to be processed and tolerance on dimensions. Whilst all processes have slightly different capabilities, there is also a large overlap - for many components there are a large number of processes which would do the job okay. So, where do we start?

Material compatibility

In product analysis (and a lot of design work), the material to be processed is often known before the process to be used has been decided. This makes life a little easier as the first thing we can do now is check what processes can be used for our chosen material - i.e. which are compatible. For convenience, processes can be split up into:

We can then use a material-process compatibility table to determine which processes are suitable.

+ : routine
? : difficult
X : unsuitable
Polymer Wood
Polymer extrusion + X  
Compression moulding + +  
Injection moulding + ?  
Blow moulding + X  
Machining Milling + X +
Grinding X X +
Drilling + ? +
Cutting + ? +
Joining Fasteners + + +
Solder / braze X X X
Welding + X X
Adhesives + + +

These tables show whether a particular material-process combination is routine, difficult or unsuitable. Using this table we can usually narrow down our choice of processing options, but how can we go further?

Technical performance

The next stage is to assess the various technical aspects of each process to see whether they will perform well. For example:

All this kind of information can only be obtained by reading descriptions of the various processes and then making informed decisions - of course experience helps!

Once all the processes that can perform well have been identified, the final step is to compare the costs of the various options...

Next: Compare the costs of competing manufacturing routes.
Back: Goals of the tutorial.

The approach to process selection given here is, of course, not the only one possible - it is geared towards the processing information provided on the TEP CD-ROM and constitutes a reasonable approach at this level. Many processing routes involve a series of manufacturing steps (e.g. cast, machine, grind and drill), but this is beyond the scope of our discussion.