A simulation-based approach for assessment of injection moulded part quality made of recycled olefins

Abstract

To produce plastic parts of high geometrical quality and dimensional stability through injection moulding process there are several key variables that must be considered. These include processing parameters such as packing time, cooling time, packing pressure, melt temperature, mould temperature and the intrinsic melt flow characteristics of polymeric materials used to produce the part. The challenge of producing high quality part is further compounded if the input polymer material is of reclaimed waste streams with inherent inconsistency in their nature. In this work, significant number of simulation-based studies are conducted using Autodesk Moldflow software to delineate the contributing issues pertinent to the part quality and achieve topological optimization by reducing critical parameters of shrinkage and warpage while ensuring overall cycle time viable for industrial production rates. Key simulation variables were obtained through experimental characterization of flow and thermal properties of the recycled olefin plastics. Different gate locations were simulated, and the best gate locations were selected for a two-gate system. These gates were provided with gate valve controllers for controlling the polymer flow to create cascaded injection moulding scenarios. Such scenarios were iterated with the objective of reducing the pressure required for cavity filling and thereby reducing the clamp force required. Optimized melt and mold temperatures of 245 °C, 20 °C were used for all the simulations performed. The result obtained from the most optimized simulation showed an average cycle time of 10.42 secs, volumetric shrinkage of 5.08%, warpage of 1.05 mm and clamp force of 79.81 tonne would be required to produce a part of 200 mm*100 mm*1.5 mm dimensions. Following a cascaded injection setup, it was shown that the clamp force could be reduced by 60.57%.