Biomedical Engineering Reference
In-Depth Information
Figure 8.23
Sample DFMA output showing internal edges are sharp. (Performed using SolidWorks)
Another aspect you may not have appreciated is that there may be some manufacturing
required by the end-user. Consider implants that require some form of cement or adhesive.
This adhesive may require some mixing and a way of placing it correctly; is this not
manufacturing? Yes it is - hence the DFM stretches to the end-user too. Have you made the
manufacturing process easy? Is it intelligible? If you perform this analysis correctly it will
make your life easier when we come to do the risk analysis later.
As a further hint, do not forget the lessons of Pareto 4 : 80% of your manufacturing costs will
be related to 20% of your components. You need to identify the 20%.
8.7.2 Design for Assembly (DFA)
The obvious starting point for multinationals putting together numerous components is to
look at the assembly process. Hence it is arguable that this could have come first; however
I suspect DFM was the first to be done. Although this has a massive impact on large batch
manufacturing (such as printed circuit boards and automobiles) it also has a massive impact
on medical devices. We shall explore…
One of the main concepts in DFA is components. Quite often the designer will use a standard
catalog and produce a plethora of different components. Too many variations of a component
cause two sets of issues.
The first is on the factory floor: too many components cause problems with purchasing
and storage, and are a frequent cause of mistakes (especially if they look the same). It
4 Vilfredo Pareto observed, in 1906, that 80% of the land in Italy was owned by 20% of the population; hence we
now know this ratio as Pareto.
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