In your explanation of CAD data transfer in DFM Concurrent Costing, you refer to "thin-walled" parts. What defines a thin-walled part?

In terms of the CAD import, the accuracy of the average thickness value is what would be affected by the part's shape. Thin walled parts will have their average thickness values estimated more accurately than thick walled parts. Regardless of the part's shape, there are still errors in the estimated value of average thickness. The thinner the part's wall, the smaller the error in the estimated average thickness. As the part's wall thickness increases, the error will also increase. We don't have an absolute value of wall thickness at which the error becomes intolerable, especially since the tolerable error depends upon the process analyzed. Some of the cost models rely on average wall thickness more heavily than others. For injection molding, the average thickness affects the calculations very little as long as the maximum wall thickness is accurately entered. In any case, just about any part that is injection molded would be considered a thin walled part and would have an average wall thickness estimated well enough.

If a criteria for determining when a part is thin- or thick-walled had to be determined, it would look something like this:

Take a cross section of the part's wall, normal to the length of the wall. The length of the wall is defined as the longest dimension of the wall. If the thickness of the wall is < 0.35 * the width of the wall, the part is thin walled. The thickness of the wall is defined as the smallest dimension of the wall's cross section and the width of the wall is defined as the largest dimension of the wall's cross section.