A three-dimensional finite element model combined with a volume tracking technique has been developed to simulate the mold filling phase in gas-assisted injection molding. The model deals with the polymer melt flow having two moving interfaces, i.e., the gas-polymer interface and polymer front. A mixed finite element formulation using four node tetrahedral elements is employed to solve the 3D Navier-Stokes equations. A robust volume tracking technique is developed to track the gas-polymer interface and the polymer front surfaces. When compared to 2D shell models, 3D modeling is capable of predicting accurately the important flow features in complex parts as well as the gas core shapes and locations.
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