Direct Additive Subtractive Hybrid Manufacturing (DASH) – An Out of Envelope Method

This work addresses a critical issue affecting the adoption of metal additive manufacturing (AM) methodologies; creating a system that can produce a mechanical product to final geometric specification. To date, almost all functional metal AM parts have required secondary processing that in many cases can more than double the cost of the final part. A Direct Additive and Subtractive Hybrid (DASH) manufacturing system using both additive and then subtractive processing has been developed so that mechanical parts can be “digitally manufactured” to meet the final required geometric accuracy. The approach includes the development of a software system to link additive and subtractive manufacturing, using extensions to the AMF format, to maintain product design features along with their tolerance specifications. It also introduces the idea of sacrificial fixtures that are automatically designed into the parts to allow subsequent fixturing in the CNC mill. Once in the milling machine, a part localization system identifies the part and its location, along with capturing the geometry of any remaining AM support material left on the part. Finally, all CNC code is automatically generated and the finishing process can be executed in a lights-out operation. This work provides a drastic reduction in post processing time and cost. It further enables expansion of metal AM and uniquely addresses the challenge of out-of-envelope hybrid manufactured parts.