The effects of different surface treatments of an injection molding screw have been investigated using light guide plates as a representative precision component. The quality of the fabricated light guide plates was compared for different screw coatings, using the stripping performance, surface microstructure and adhesion strength as criteria. In addition, the results obtained using different combinations of screw coatings were analyzed in order to identify the optimum screw surface treatment method for the large scale production of polycarbonate light guide plates. It was found that light guide plate parts fabricated using a screw with a TiAlN/Cr multi-coating had the best performance, with a defect percentage of only 0.11%, much lower than the value of 19.21% obtained using a screw with a conventional hard chrome coating.

Keywords: multi-coating; screw surface treatment; injection molding quality; light guide plate