Does DFMA software accurately estimate the cost of precision machined components, especially low volume ones, and suggest lower cost alternative configurations or designs for such components?

There are two approaches which can be taken when machining parts with tolerance and flatness requirements on the order of microns. Depending on the part's shape and material, it is most common to perform some sort of finish grinding operation after rough machining is carried out. DFM Concurrent Costing includes such grinding operations and can therefore accurately estimate the cost of parts processed in such a way. If a part cannot be ground due to its material or shape, another approach to precision machining is to utilize very rigid machine tools and work holding devices and then minimize forces required by taking very small cut depths at very slow feed rates. All of these factors are adjustable in the software and as a result, the software will accurately estimate the cost of parts processed in this way.

When parts are manufactured in very low volumes, the setup time required becomes a much more important cost driver than it is in normal volume production. In fact, in prototype production, setup time is usually one of the primary cost drivers. The DFM software has been used to estimate the cost of parts with a life volume of one part and the results have been used in arriving at very good cost estimates. Many of these parts were machined components with very tight tolerances and run-out requirements.

In terms of suggesting a lower cost alternative configuration, typically the DFM software allows you to estimate the cost of alternative ideas so you can determine which alternative would be most cost effective. Specifically, the machining processes allow you to estimate the cost of every feature on the machined part. Normally, after completing an analysis it becomes fairly obvious which areas you should be focusing on when coming up with alternative ideas because you will be able to determine what each part feature costs and which operations contribute most to the feature cost. After using that information to generate an alternative part design, you can estimate the cost of that alternative in the software. Normally when this type of analysis is carried out, some costs will decrease with the alternative part design and some will increase. With the software you can determine the magnitude of these changes in cost and determine if, overall, the alternative is more cost effective or not. If it turns out that the alternative is not more cost effective, at least the original design is justified.

If you work with assemblies, the Design for Assembly (DFA) software makes suggestions for lower cost alternatives. DFA steers designers away from creating assemblies with a large number of single function parts by suggesting that an assembly's functional requirements be met with a smaller number of multi-functional parts. Normally, the suggestions presented by DFA will result in a decrease in assembly costs. It is important, however, to also do DFM analyses of the individual parts within the alternative design to determine if the alternative is really more cost effective overall. Normally when a before-and-after comparison like this is done, some costs increase and some costs decrease. But again, with the software, you can determine the magnitude of these changes in cost and determine if the alternative is more cost effective than the original.