A 3-D finite element model for gas-assisted injection molding: Simulations and experiments

To gain a better understanding of the gas‐assisted injection molding process, we have developed a computational model for the gas assisted injection molding (GAIM) process. This model has been set up to deal with (non‐isothermal) three‐dimensional flow, in order to correctly predict the gas distribution in GAIM products. It employs a pseudo‐concentration method, in which the governing equations are solved on a fixed grid that covers the entire mold. Both the air downstream of the polymer front and the gas are represented by a fictitious fluid that does not contributeto the pressure drop in the mold. The model has been validated against both isothermal and non‐isothermal gas injected experiments. In contrast to other models that have been reported in the literature, our model yields the gas penetration from the actual process physics (not from a presupposed gas distribution). Consequently, it is able to deal with the 3‐D character of the process, as well as with primary (end of gas filling) and secondary (end of packing) gas penetration, including temperature effects and generalized Newtonian viscosity behavior.