Optimum ejector system design for plastic injection moulds

Abstract

Injection moulding is a technology predominantly used for processing thermoplastic polymers. The injection moulding cycle for thermoplastics consists of several major stages. At the end of the injection cycle the plastic moulded part has to be ejected when the injection mould opens. Since the ejection force from the ejector plate is usually great enough for the required releasing force, mould designers usually neglect the balance of the ejection force which is exerted on the sticking surface. Part deformation or damage might occur due to the unbalance of the ejection force. This paper describes an efficient algorithm for optimizing the arrangement and selection of ejectors. The required releasing/ ejection force should be proportional to the area of the sticking surface. Furthermore, a CAD environment has been developed to facilitate the ejector system design. The processes for optimization and implementation of the algorithm are described in detail and a case study is presented to illustrate the procedure.