Influence of processing parameters on residual stress in injection molded parts

Abstract

Residual stresses are the source of shrinkage and warpage of the parts manufactured with injection molding technology and strongly influences its final dimensions. In complicated parts residual stresses are very difficult to predict without numerical tools, along with the warpage, what leads to problems with manufacturing parts that meet the expected tolerances. Residual stresses have also strong influence on mechanical performance of the part, where its high value can results with self-cracking during ejection from the mold. In this work numerical simulations injection molding process were performed to analyze the presence of residual stresses in manufactured plastic parts by this technology. Numerical simulations were used to find the relations between the processing parameters and the distribution and magnitude of residual stresses. Occurrence of residual stresses were analyzed with new 3D residual stress model implemented in Autodesk Moldflow® software. Qualitative strain-optics observations were performed to verify the differences between different sets of processing parameters. From investigated parameters the strongest influence on residual stresses was observed with packing time, while the weakest influence was observed with injection time.