Re-Thinking Design Methodology for Castings: 3D Sand-Printing and Topology Optimization

Abstract

Additive manufacturing of sand molds and cores for metal castings, often called 3D sand-printing (3DSP), is an efficient “freeform” fabrication process that enables rapid production of sand metal castings. The ability to create highly complex molds and cores for advanced metal casting geometries via 3DSP provides unparalleled design freedom, particularly for low-volume production. However, there is a need to thoroughly understand the opportunities and restrictions of 3DSP in a systematic approach similar to well-established design guidelines for traditional sand casting. This study presents a knowledge-based design framework for 3DSP with the goal of developing new part design guidelines under such 3DSP framework. In particular, constrained topology optimization approach for the part redesign is developed for 3DSP. The presented design framework is compared with traditional sand-casting rules and validated through a case study on an existing metal component. Advantages of the developed 3DSP design framework are illustrated and validated through a case study where a 30% improvement in factor of safety and a 50% reduction in weight of a mechanical part is achieved. Other advantages, such as reduced lead time and production cost, are also observed. This research provides the first known investigation into systematic implementation of simultaneous constraints of 3DSP sand-casting rules mechanical strength through the integration of topology optimization and novel design rules to castings via 3D-printed molds. 3DSP also eliminates multiple design constraints in conventional mold-making and core-box fabrication. Findings from this study can be applied for a wide range of alloy systems, part geometries and loading conditions for sand castings in industrial applications.