Eliminating occluded voids in additive manufacturing design via a projection-based topology optimization scheme

Design for additive manufacturing (AM) requires knowledge of the constraints associated with your targeted AM process. One important design concern is the unintentional trapping of parasitic mass in occluded void geometries with either uncured or non-solidified material, or in some cases, sacrificial support material. These occluded features create the need to physically alter the optimal topology to remove the material. In this work, a projection-based topology optimization design formulation is proposed to eliminate occluded void topological features in optimal AM designs. The algorithm is based on the combination and enhancement of two existing algorithms: a projection-based, overhang-constrained algorithm to design self-supporting structures in AM, and a void projection algorithm to design topologies through control of the void phase. The combined algorithm results in topologies with void regions that always possess an exit path to predefined outer surfaces – i.e. drainage pathways. Solutions are first demonstrated in two dimensions, with increasing design freedom allowed through algorithm enhancements. The algorithm is then adapted to 3D, adopting a multi-phase TO approach to not only regain control of the solid phase length scale, but also to drive toward superior performing topologies with minimal impact on the part performance.