Experiments and simulation of injection molding with microstructures

Injection molding has the potential for economical mass-production of polymer products with microstructures. Conventional 2D midplane simulations using the Hele-Shaw approximation are not able to describe the local flow for the microstructures. A hybrid 2D simulation code combining solutions of the general momentum equation in the microstructure region and the Hele-Shaw model in the main flow region is developed. This method is able to obtain a good resolution and requires less computational time than the full 3D momentum equation approach. The mold-melt heat transfer coefficient and injection speed are found be the very important factors to determine the filling depth. A series of injection molding experiments is carried out and comparison is made between the experimental measurements and simulation results. A commercial simulation code DEFORM is also tested in the simulation of micro injection molding because it can calculate the stress distribution in the mold piece and mold deformation. The theology data is input as the plastic property of the material.