RUN TIME OPTIMIZATION IN INJECTION MOLDING SIMULATION WITH ADAPTIVE AND SELECTIVE GRID REFINEMENT

Computational Fluid Dynamics (CFD) has been successfully utilized in the polymer processing industries in various processes, e.g. the polymerization of thermoplastic polymer materials and injection molding for the understanding of the underlying physical phenomena. Especially in injection molding, the reduction of the development time of tools and machines has been one of the most important issues in the last decades. A large variety of processed materials is available with varying properties. Most importantly the material behavior differs from usual Newtonian fluids in the non-Newtonian behavior and the order of magnitude of the viscosity (≈ 10-10000 Pas). The value can vary depending on the shear-rate, the temperature as well as the pressure. With the addition of the compressibility of the liquid polymer, machines have to be able to handle considerable changes in processing conditions. A progressive trend has been emerging during the last years, where the computer-aided optimization has been proven as one of the key steps in the development of machines and processes in injection molding. In simulations the process can be visualized three-dimensionally as opposed to experiments, where processing conditions can only be monitored at certain locations. Additionally, all quantities (e.g. density, viscosity, shear-rate, velocity etc.) needed for the simulation can be evaluated as opposed to only pressure or temperature values in experiments. Due to the complexity and interdependency of quantities of fluid dynamic and thermal processes during the discontinuous process it has to be guaranteed, that a wide variety of phenomena can be modeled correctly. It is important to focus on dominant phenomena in the process in order to reduce calculation time for the industrial application. In this work an approach with adaptive and selective grid refinement it proposed in order to dynamically change the grid resolution during the process. With this approach it is possible to use a refined grid resolution in regions of interest and keep a coarse mesh in regions, which do not dominantly contribute to the process. With the utilized models experimental validation shows promising agreement during the entire discontinuous process of injection molding. The achieved good agreement promises the possibility to use OpenFOAM as an intrinsic part of the development stage of injection molding tools and machines as well as of a certain machine optimization simulation methodology.