Test methodThe impact of process parameters on test specimen deviations and their correlation with AE signals captured during the injection moulding cycle

The aim of this work was to investigate the influence of six injection moulding process parameters on the post-moulding shrinkage and warping of parts made from polypropylene filled with calcium carbonate, as used in large quantities throughout the automotive industry. For experimental purposes, standard test specimens were used for the determination of post-moulding shrinkage and warping. Each experiment was observed precisely through the measurement of acoustic emission (AE) signals and in-cavity pressure. We scanned each test specimen using an optical 3D scanner for accurate measurement of post-moulding shrinkage and warping. The optimal set of parameters that provides minimal post-moulding shrinkage and warping, was determined by the Taguchi method, together with nominally-the-best (type II) quality characteristic. The most influential parameter was statistically obtained through analysis of variance, which showed that packing pressure had the largest impact. The results from the measured AE signals showed clear correlation with the post-moulding shrinkage and warping, indicating the possibility of on-line monitoring the adequacy of the process by capturing AE signals.