Self-supporting topology optimization method for selective laser melting

Abstract

The design of self-supporting structures is critical for the selective laser melting (SLM)-based 3D printing techniques. However, the control of the overhang feature conflicts with the mechanical performance of the structure. This paper proposes an approach to achieve the self-supporting structural design to facilitate the SLM process. Printable overhang heights of samples under various overhang angles are investigated through experimental tests, and the maximum overhang heights are mathematically related to the corresponding critical overhang angle. Subsequently, this relationship is incorporated into the topology optimization formulation to realize the optimized self-supporting structures. The SIMP (solid isotropic material with penalization) method is used to conduct topology optimization. An effective filtering strategy with the overhang restrictions is developed to eliminate the material parts that cannot be supported from below. A typical beam structure to maximize the stiffness is used as a numerical example to demonstrate the proposed method. The numerical results show that the restrictions with both the overhang angles and heights can generate optimized structures with better performance than those only with the overhang angle constraint. In addition, prototypes are used to validate the manufacturability of the topologically optimized designs.