Integrated Simulations of Structural Performance, Molding Process and Warpage for Gas-Assisted Injection Molded Parts

Integrated simulations of part structural performance, processing characteristics and warpage for the gas-assisted injection molded parts were carried out using a unified CAE model. An analysis algorithm based on DKT/VRT elements superimposed with beam elements representing gas channels of various section geometry was first developed to evaluate part structural performance. During melt/gas filling stage, a mixed control-volume/finite-element/finite-difference method combined with dual-filling-parameter technique was implemented to trace the advancements of melt and gas fronts. For the prediction of secondary gas penetration, flow model of isotropic-shrinkage origin was introduced. Cooling analysis was executed utilizing cycle-averaged boundary element approach considering hollowed core geometry within gas channels. Thermal-induced residual stress was then calculated to predict part warpage. The analysis accuracy from this unified model of 2 1/2-D characteristics show reasonable accuracy when compared with molding experiment and part bending tests. The only difference between process simulation and structure/warpage analyses is that different values of equivalent diameters assigned to beam element representing gas channel should be used, respectively.