Shape deposition manufacturing with microcasting: Processing, thermal and mechanical issues

Shape deposition manufacturing (SDM) is a solid freeform fabrication (SFF) methodology for automatically building up material layers to for three-dimensional, complex-shaped, multi-material structures. Microcasting is a molten metal droplet deposition process which is able to create fully dense metal layers with controlled microstructures. SDM combines microcasting with other intermediate processing operations, such as CNC machining and shot peening, to create high quality metal parts. In this paper, a description is given of SDM and;the microcasting process. An overview of thermal and mechanical issues associated with SDM and microcasting is presented, including the control of interlayer metallurgical bonding through substrate remelting, the control of cooling rates of both the substrate and the deposited material and the minimization of residual thermal stress effects. Thermal models are used to study the issue of localized remelting of previously deposited material by newly deposited molten droplets to achieve metallurgical bonding. Mechanical modeling provides insight into residual stress build-up during part manufacture and residual stress-driven debonding between deposited layers.