Additive Manufacturing Supports the Production of Complex Castings

Additive manufacturing is being used in a variety of ways to support the production of complex castings. Some of the common additive manufacturing processes include fused filament fabrication, vat photopolymerization, powder bed fusion, binder jetting, and material jetting. In this paper, the authors discuss the use of (i) binder jetting technology to fabricate sand molds for casting complex, cellular structures and (ii) fused filament fabrication & vat photopolymerization to produce complex investment casting patterns. Binder jetting of foundry sand molds allows the realization of cast structures that are impossible to mold using conventional methods. The structures are lightweight, multi-functional and may provide exceptional blast protection. With regards to investment casting, wax is currently the primary material used for producing expendable patterns due to a desirable combination of thermal expansion, thermal conductivity and melting point. However, wax is not a typical printed material. A variety of polymers are available for additive manufacturing and, as would be expected, only a few are suitable for use as expendable patterns for investment casting. The best polymers for use as expendable patterns for investment castings are PMMA, epoxy resin containing a reactive diluent and ABS.