Practice vs. laboratory tests for plastic injection moulding

Different types of anti-sticking coatings have been applied industrially on injection moulds for various types of plastics. Very often these tests are being done on a trial-and-error basis and results obtained are difficult to interpret. WTCM/CRIF has developed laboratory equipment where the injection moulding process can be simulated and demoulding forces and friction coefficients can be measured. These measurements were compared with surface energy calculations of the coated surfaces and of the plastic materials in order to find a correlation. Using this approach it must be possible to make an easy and cheap selection of promising coatings towards plastic injection moulding. Another important advantage is that the understanding and modelling of the mould–plastic interface becomes possible. This new way of coating selection for plastic injection moulding has been demonstrated for various PVD coatings and verified for different industrial injection moulding applications.