Metal casting using soluble pattern produced via additive manufacturing

Conventional metal (sand) casting requires solid patterns consisting of two halves (cope and drag) prepared to remove the pattern. The approach is simple but leads to numerous steps and mismatch errors. Also, sand, a porous material, is very sensitive to vibration and susceptible to cracks and breakage. This research presents a novel approach for investment metal casting, where a water-soluble material is used for pattern generation using material extrusion additive manufacturing (AM). As a proof of concept, a semi-complex non-prismatic geometry with various dimensional features is physically realized using this soluble pattern casting (SPC) technique. The pattern is designed and 3D printed out of a water-soluble acrylonitrile butadiene styrene (ABS) thermoplastic using an indigenously fabricated screw extrusion-based AM setup. A ceramic mould is created from plaster of Paris (PoP) around the soluble pattern, generating the mould cavity on further dissolution. A heated water bath with added turbulence via solid vibrations assisted the dissolution process. The final geometry is realized by firing the mould cavity followed by metal pouring. Various geometrical features and intricate details, such as layer lines, are satisfactorily replicated from the 3D-printed pattern to the final metal casting. The dimensional accuracy and surface finish are analysed along the process, starting from the printed pattern to the ceramic mould cavity and the final metal cast part. The presented method has applications in investment casting (IC) industries as it can help significantly reduce the lead time and provide excellent dimensional conformance and geometrical replication from the pattern to cast.