TABLE OF CONTENTS In this process, a component termed a preform is placed into the tool of an injection moulding machine. A second material is then moulded onto or around the preform. Two methods fall under this category: insert moulding and lost core moulding.
Insert moulding with plastics is a two-step process whereby a first preform component is placed into the open mould cavity. Injection then proceeds as with traditional moulding methods with injection of a molten plastic onto the preform. This process is not limited to two material components and the resultant mouldings can be transferred in this way until the required number of layers is achieved. Inserts can be loaded by hand or by the use of robots. Inserts must be accurate in both their dimension and their placement into the over-moulding tool to prevent tool damage and provide accurate registration of one material on another. A means must also exist to hold them in place within the tool. In this way it has similar requirements to that of in mould lamination techniques commonly used to decorate plastics with films or foils, details of which can be found in a specialist Rapra Review Report [4] and will not be covered further here.
The lost core technique, like insert moulding, is often used in combination with metals as well as plastics. It produces a hollow component similar to those produced by techniques such as extrusion blow moulding or gas assisted injection moulding. This...
