Integrated simulations of structural performance, molding process, and warpage for gas‐assisted injection‐molded parts. I. Analysis of part structural performance

Abstract

Whether it is feasible to perform an integrated simulation for structural analysis, process simulation, as well as warpage calculation based on a unified CAE model for gas-assisted injection molding (GAIM) is a great concern. In the present study, numerical algorithms based on the same finite element mesh used for process simulation were developed to simulate the bending performance of gas-assisted injection-molded parts. Polystyrene and nylon plates designed with five different channel geometries were gas-assisted injection-molded. Part flexible strength was measured via bending tests. It was found that part stiffness basically increases linearly with the inertia moment of the plate. Gas channel design results in part structural reinforcement by introducing an additional moment of inertia determined by the shape and the dimension of the channel section as well as the hollowed-core geometry. An analysis algorithm based on VRT/DKT elements superimposed over beam elements representing gas channels of various section geometries was developed to evaluate part bending behavior. An equivalent diameter was assigned to the beam element so that both the original gas channel and the circular beam have the same moment of inertia. The simulated results were also verified with ANSYS 3-D and 2 ½-D analysis. The simulations show reasonable accuracy as compared with measured results and predictions from ANSYS. This investigation indicates that it may be feasible to achieve an integrated simulation for GAIM under one CAE model, resulting in great computational efficiency for industrial application. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 417–428, 1998