Compression Moulding Process – An Overview

mechanical engineering

Known as one of the oldest plastic processing methods, compression moulding (CM) is widely used in plastic processing plants due to its advantages which are lesser seen in other methods. Though injection moulding is the most widely used process, it lacks in some properties which can be achieved in compression moulding. This process is used to give a desired shape to the plastic with the use of high temperature and pressure. It can be used for thermoplastics as well as for thermosetting. In plastics, Thermosets and composite plastics have low melt flow index and the fact that they require high pressure to cure, compression moulding is most common process selected. The finished product from compression moulding is seen to be tough and hard to sustain various loads applied and the surface can be made smooth as per requirement. The scrap produced (flash) is lesser than injection moulding (runners and gates produced during the process). The process setup includes the plastic preform (either powder or tablets) is usually preheated is placed in the heated mould cavity. Heating of mould is done to catalyze the curing reaction. Pressure is then applied with help of a power press for a certain period of time known as curing time. The part thus takes the shape of mould cavity and is then ejected from the mould with ejector system. For an optimum utilization of this process, various parameters are to be controlled such as part geometry, part material, mould quality, mould temperature, curing time, clamping pressure, breathe cycle, preheating and charge quantity. This paper covers a brief overview of the compression moulding process followed by the controlling process parameters.

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