The Additive Manufacturing (AM) of injection molding inserts has gained popularity during recent years primarily due to the reduced design-to-production time and form freedom offered by AM. In this paper, Topology Optimization (TO) is performed on a metallic mold insert which is to be produced by the Laser Powder Bed Fusion (LPBF) technique. First, a commercially available TO software is used, to minimize the mass of the component while ensuring adequate mechanical response under a prescribed loading condition. The commercial TO tool adopts geometry-based AM constraints and achieves a mass reduction of ~50 %. Furthermore, an in-house TO method has been developed which integrates a simplified AM process model within the standard TO algorithm for addressing the issue of local overheating during manufacturing. The two topology optimized designs are briefly compared, and the advantages of implementing manufacturing constraints into the TO algorithm are discussed.
Introduction@en

Numerous challenges of additive manufacturing (AM) are tackled in the European Horizon 2020 project PAM^2 by studying and linking every step of the AM process cycle. For example, PAM^2 researchers from the design, processing and application side have collaborated in this work to optimise the manufacturability of metal AM parts using an improved Topology Optimisation (TO) approach, including a thermal constraint. Additionally, the project is focusing on modelling, post-processing, in- and post-process quality control and industrial assessment of AM parts, with the aim of moving beyond the state-of-the-art of precision metal AM. @en

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.@en