Gas assisted injection moulding: Experiment and simulation. Industrial machine experimental studies of the effect of process variables on gas bubble formation, and with simulation based upon a pseudo-concentration method.

摘要

The gas assisted injection moulding process is an important extension to conventionaludinjection moulding. Gas assist can be applied in a number of ways, butudhere the penetration of a gas bubble through the polymer melt is of interest. Aud3D fi nite element implementation of a pseudo concentration method is employedudto simulate the primary penetration of the gas bubble. The wall thickness predictionudis an important result since the extent of bubble penetration is sensitiveudto the remaining melt fraction. A number of methods for experimental measurementudare developed to measure characteristics of the gas assisted injectionudmoulding process dynamics and product. Key process variables, on an industrialudgas-assist machine, were measured and analysed, leading to an empirical modeludfor wall thickness prediction. Gas delay time and injection velocity are shown toudbe most influential in controlling residual wall thickness. Simulation results areudevaluated against the empirical model. The trends observed, for simulation andudexperiment, in wall thickness after changes in process variable settings are foundudto agree qualitatively. The wall thickness prediction is found to be within 10% ofudthe experimentally obtained measurements.