Metal direct prototyping by using hybrid plasma deposition and milling

Rapid prototyping (RP), especially metal direct rapid prototyping, brings engineers a new model to fabricate parts more difficultly than conventional machining. Furthermore, the surface quality and the dimensional accuracy of the parts manufactured using the simplex metal direct prototyping or tooling approach are even lower than that of the conventionally machined parts. To overcome these deficiencies, this paper presents a new metal direct RP approach, called hybrid plasma deposition and milling (HPDM) using plasma deposition as an additive and conventional milling as a subtractive technique, which synthesizes the advantages of both processes. Compared with other metal-deposition ways, such as laser or electron beam deposition processes, the plasma deposition used in the current HPDM is the most economical one. Simultaneously, the precision of the manufactured parts is ensured by the compounding CNC process which assists to remove the staircase caused by the layered manufacturing principle and the allowance of the near-net shape deposited by plasma deposition. The initial results of the process development and the characteristics of the parts fabricated by this process are reported in this paper. Using a set of optimized process parameters obtained in this study, a group of metal parts, such as metal hollow vases, were trial-manufactured. The surface roughness Rz was obtained 2.32 μm and the dimensional accuracy was controlled within ±0.05% of the metal part. With these results obtained, the microstructure was then examined to prove the applicability of the HPDM process to direct fabrication of metallic prototypes and tools.