Topology optimization of an injection mold insert with additive manufacturing constraints

This work presents the redesign of an injection molding metal insert to be prototyped by the selective laser melting (SLM) process. The case study has been topology optimized to minimize its total mass while keeping the maximum von Mises stress and maximum displacement under load condition below chosen thresholds. Particular attention has been given to properly select the design space for the topology optimization (TO), taking care both of the industrial requirements and the simplifications needed to run the TO code. While the main TO has been performed with a commercially available software, a secondary optimization has been tried with in-house code to address the problem of local heat accumulation during the SLM manufacturing. Heat accumulation is a well-known issue for design features like overhangs and thin sections, and can cause issues such as poor surface finish and dross formation. A novel TO formulation is therefore employed to control AM associated local overheating by imposing a thermal constraint. The “hotspot indicator” is integrated with the standard compliance minimization TO problem, and a new design of the mold insert without local overheating is produced. Finally, a comparison between the two TO redesigns is briefly discussed.