Evaluation of 3D printed foam patterns for hybrid lost foam casting of A356 alloy

Lost Foam Casting (LFC) is an economical method of producing high-yield metal castings by evaporative decomposition of expanded polystyrene (EPS) patterns during pouring. The method can be used to cast intricate patterns such as manifolds, engine blocks with internal cavities, and other complex geometries. To make the EPS foam patterns, specialized molds and tooling must be machined, making this process economical only for highvolume production. The present research presents a Hybrid Lost Foam Casting (HLFC) process, which leverages 3D printing technology to manufacture light weight foam patterns using fused filament fabrication (FFF). Thinwalled plate patterns were 3D printed using a foaming polylactic acid (PLA) feedstock with a low-density infill, achieving a bulk pattern density of 0.044 g/cm3, twice that of traditional EPS foam. Aluminum alloy A356.2 was cast using foam PLA and EPS patterns of the same geometry, but under different combinations of casting parameters of traditional LFC. Tensile and microscopy samples were machined from the plates for comparative analysis of mechanical properties and microstructure. Yield strength was essentially equal for all samples averaging 96.7 MPa for EPS and 95.7 MPa for PLA-based castings. Additionally, a complex valve body pattern was 3D printed, laser-scanned, and cast for dimensional analysis. Over 90 % of the valve body surface was observed to fall within a tolerance zone of +/- 0.2 mm.