Optimising the gas-injection moulding of an automobile plastic cover using an experimental design procedure

The main objective of this work was to optimise the production of a plastic automobile door plastic cover using computer simulation and the application of statistical experimental design. Due to the thickness and cover dimensions, the full-shot gas-assisted injection moulding was considered the most suitable manufacturing process. Different fabrication possibilities were investigated changing either the melt or the gas-injection point location. The best alternative was achieved with a sole central point injecting the melt and two adjacent lateral points applying gas. Two overflow channels were situated in part edges to collect the melt displaced by the gas. The experimental design technique was carried out to obtain the combination of variables that provide a greater channel voiding and better thickness uniformity. Gas channels were found to be completely empty after carrying out the simulation, implying that part fabrication was assured, although differences in wall thickness along the channel path were however detected. Results showed that no control of wall thickness was possible through the selected processing parameters. Regarding the displaced melt volume and part weight the controlling parameters were the melt temperature, mould temperature and gas pressure.