Injection Moulding of Plastic Parts with Surface Microstructures

In this study the replication of surface microstructures in injection moulding has been explored for Polypropylene at low mould temperatures. The issue of the physical mechanisms controlling replication has also been addressed. The mould micro geometries applied are essentially 2½D rectangular structures with heights of 9 µm and aspect ratios from 0.2 to 1. For topographical characterisation a confocal laser scanning microscope was used. The injection moulding process conditions were varied over the recommended process window for the material, and the process was analysed using commercial simulation software. Evidence suggests that step height replication quality, in a certain scale range, depends linearly on structure width. Further it was found that in this range, the replication quality depends strongly on process conditions.