What are the machine selection criteria in DFM Concurrent Costing?

They depend on the process. When the software is using setups from the Machine Library, and when Automatic selection of machines is turned on (see this checkbox response field at the setup level on the process chart), the software will select the least expensive machine with the minimum processing characteristics needed to process the part. For instance, the stamping press will have an adequate bed length and width, and press force capable of performing the operations.

If you deselect Automatic selection, and manually choose the setup you want, you will receive a warning if the machine capacity is not adequate to processing the part.