Structural Optimization of Injection Molds With Lattice Cooling

Lattice cooling (LC) is a novel approach to improve the thermal and mechanical performance of an injection mold, thus challenging the traditional conformal cooling approach. By using current Additive Manufacturing (AM) technologies, LC with highly complex structures is possible. In this study, the design concept of LC is further improved by implementing a thermo-mechanical topology optimization method. This method utilizes porosity-dependent heat conduction, convection to dissipate internal heat generation, while maintaining mechanical stability of an injection mold. The porosity and shape of each lattice unit cell (LUC) in LC channels is determined by employing this method. A homogenization method is used to determine the porosity dependency of mechanical elasticity and heat conductivity, a surrogate model is used to determine the porosity dependency of heat convection and internal heat generation. The method firstly determines the porosity distribution of LUCs, then optimizing the bulk moduli of each LUC using inverse homogenization to improve the stability of LC. An example is presented to illustrate how to use the proposed approach to design LC sections for an injection mold with a given average porosity. The result shows, by applying the proposed approach, the thermal performance is improved 30 % compared to a uniform LC channel with the same average porosity, without decreasing the mechanical performance. The resulting optimized lattice made possible by utilizing Additive Manufacturing technologies.