Insert moulding is used to create a moulded 'assembly', by introducing a pre-formed part - or an insert - into the moulding process. The insert is commonly made from metal, with the plastic or rubber then moulded around the insert to form an assembly incorporating parts made from multiple materials.
Insert moulding usually takes the form of injection moulding, with the insert mounted inside the mould tool cavity. Molten plastic is then injected into the mould, where it fills the cavity around the insert and is left to cool. Once solidified, the plastic will become bonded to the insert and the finished assembly is retrieved from the mould.
Although the lead times for insert moulding will be slightly longer than that of straightforward injection moulding, insert moulding takes a lot of secondary assembly processes out of the equation by assembling the components during the moulding process. As injection moulding is most commonly used, this means that a wide range of plastics can be used such as polycarbonate, polypropylene, HDPE, LPDE, nylon and ABS.