The development and manufacturing of ejection systems in injection moulds can be a complextask, particularly when the parts have long ejection paths. During the injection of tubular- or box shape parts,the shrinkage is constrained by the mould. The mouldings shrink against the core, inserts or pins, thus, duringejection, it will be necessary to overcome the frictional forces resulting from the shrinkage. Understanding theejection forces could be a useful contribution to improve ejection systems designs and guarantee the structuralintegrity of the mouldings. This information could be even more useful in the processing of thin-walled partswhich are more prone to damage during ejection. Frictional forces could be decreased by using specific coatingsin the mould core and by optimization of the processing parameters. This study describes the use of DLCand WS2 coatings and the effect of mould temperature in the ejection forces of tubular mouldings inpoly(lactic acid) (PLA) and polystyrene (PS). The studies were based on tubular cup shaped mouldings (60mm diameter, 60 mm length, 0.5 mm thickness and 0.35 º draft angle).
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