During ejection, friction forces are induced at the mould-part interface, so the ejection force exerted by the ejector pins is basically required to overcome friction and to remove the box. Therefore the analysis of the ejection process must be based on the constraining and friction forces resulting from the mould-part interaction during solidification and ejection. The influencing factors relevant to the ejection of injection mouldings must be considered. These include the moulding shrinkage, the mechanical properties of the contacting materials and how the coefficient of friction depends on all the other parameters (Figure 2).