Evaluation of 3D printed pattern material for heat-hardened inorganic molds

Inorganic binders for sand moulding are currently of high interest due to needs for lesser environmental impact and emissions. In this study, a heat hardened solid inorganic sodium silicate binder was tested with a 3D printed resin material to see how the use of such material affected a silica mould’s quality, e.g. surface roughness. Results were compared to moulds made with metallic patterns. The unmodified binder had sticking issues when used with a metallic pattern, resulting in a rough as-moulded surface. Such issues were not seen with the printed resin patterns, hinting also at good performance with binders that contain performance increasing additives. The resin pattern material has Heat Deflection Temperature (HDT) of 230 °C, enabling use of inorganic binders that require temperatures between 160…200 °C to harden and dry. Additive manufacturing of such materials also allows designs for other hardening techniques than furnace heating, such as microwave heating. Moulds hardened with microwaves did not exhibit sticking issues. Additive manufacturing of tooling is a potential source of geometrical variation in final castings, studied also in this work. In general, switching from traditional sand moulding patterns used with organic binder systems to inorganic systems, the patterns and core boxes need to be replaced by new ones made of metallic or other heat resistant material. The studied material is a promising option for such a switch, especially when also the complex shaped enabled by additive manufacturing is required.