Multi-material topology optimization of additively manufactured thermoplastic molds for heat transfer enhancement

Abstract

Abstract. For low-volume scale manufacturing of plastic parts, thermoplastic molds made of polymers and printed by additive manufacturing (AM) technology have proved to be a viable alternative to replace expensive and time-consuming steel molds. Nevertheless, due to the relatively low thermal conductivity of the polymers employed for their manufacture, not only the cycle times are increased, but also the surface temperature homogeneity is affected during the cooling of the part, potentially impacting its final quality. On the other hand, the latest advances in AM technology allow the 3D printing of parts with two polymers of different thermophysical properties, opening the possibility for heat flux manipulation within the thermoplastic mold. This work is devoted to the numerical implementation of a topology optimization (TO) methodology to enhance the temperature homogeneity of an injected part during the cooling phase. The proposed scheme relies on the usage of the gradient-free particle swarm optimizer (PSO) in conjunction with filtering techniques to obtain a feasible-to-manufacture multi-material thermoplastic mold. The TO strategy is thoroughly validated against gradient-based techniques found in the related literature conceived for heat flux manipulation in the transient regime. The results show outstanding improvements in the temperature homogeneity of the part when strategically placing the low-conductivity polymer in easy-to-cool regions and the high-conductivity polymer in regions that cool down slower. We further report in this work the possibility of achieving standard deviation values like those obtained by a steel counterpart.