Casting of topologically optimized components utilizing additive manufacturing

Abstract

Casting is a widely-used metalworking method that is valued for its benefits in product manufacturability, repeatability, versatility, and low cost. Although casting capabilities are always improving, there are still many limitations in component design due to the constraints of conventional pattern fabrication methods. Topology optimization is an innovative design approach that optimizes the material layout of the designated geometry. Optimized designs are often too complex to manufacture with standard casting, machining, or other fabrication processes, forcing the utility of topology optimization to remain solely in preliminary design. These designs often require alteration to improve manufacturability, therefore diminishing the full potential benefits of the topology optimization. Additive manufacturing (AM) technologies, such as 3D printing, are capable of fabricating topologically optimized components without design alteration. However, the limited material selection offered by 3D printers inhibits the performance of printed components. Combining AM technologies and casting allows the possibility to manufacture topologically optimized components using typical casting alloys.

This work looks at current casting and AM technologies, the background of topology optimization, practical work on numerous original optimized designs, the adaption of selected designs to casting methodology, analysis of selected designs using casting simulations, and fabrication of selected designs via investment casting and sand mold casting. Results showed that the collaboration of casting and AM technologies allowed the fabrication of topologically optimized components without the need for significant design alteration. However, defects such as porosity and cracking occurred in both the simulations and physical castings of the components. These complications were likely caused by large variance in the size of adjacent features and by the presence of many flow fronts during pouring. Findings in this work highlight at least the following; optimized components can be produced by casting, although the methods and software need to develop further before the full potential of this approach can be reached. These issues could be mitigated through further study and optimization of the casting processes.