INTEGRATED SIMULATIONS OF STRUCTURAL PERFORMANCE, MOLDING PROCESS, AND WARPAGE FOR GAS-ASSISTED INJECTION-MOLDED PARTS - III - SIMULATION OF CYCLIC, TRANSIENT VARIATIONS IN MOLD WALL TEMPERATURES

Whether it is feasible to perform an integrated simulation for structu ral 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 th e same CAE model used for process simulation regarding filling and pac king stages were developed to simulate the cooling phase of GAIM consi dering the influence of the cooling system. The cycle-averaged mold ca vity surface temperature distribution within a steady cycle is first c alculated based on a steady-state approach to count for overall heat b alance using three-dimensional modified boundary element technique. Th e part temperature distribution and profiles, as well as the associate d transient heat flux on plastic-mold interface, are then computed by a finite difference method in a decoupled manner. Finally, the differe nce between cycle-averaged heat flux and transient heat flux is analyz ed to obtain the cyclic, transient mold cavity surface temperatures. T he analysis results for GAIM plates with semicircular gas channel desi gn are illustrated and discussed. It was found that the difference in cycle-averaged mold wall temperatures may be as high as 10 degrees C a nd within a steady cycle, part temperatures may also vary similar to 1 5 degrees C. The conversion of gas channel into equivalent circular pi pe and further simplified to two-node elements using a line source app roach not only affects the mold wall temperature calculation very slig htly, but also reduces the computer time by 95%. This investigation in dicates that it is feasible to achieve an integrated process simulatio n for GAIM under one CAF: model, resulting in great computational effi ciency for industrial application. (C) 1999 John Wiley & Sons, Inc.