Composite injection moulding can be employed for two or more components, whereby the complexity of the mould rises significantly with the number of the components.
Composite injection moulding is particularly advantageous when production can be completed in one mould without intermediate opening of the machine and without further transportation of the pre-moulded part. However, it is a disadvantage because production proceeds in a strictly phased sequence, while simultaneous operations are possible with multi-component injection moulding. For moulded parts which, because of their geometry, may be produced with both processes, a parts-specific economic study is necessary to establish the more favourable process.

Standard multi-component injection moulding machines are used; as all the necessary movements are performed inside the mould, the machine technology is the same and no exterior accessories are required. However, it must be ensured that the machine which is used has an adequate number of available and programmable core pulls for actuating the sliding cores.

During composite injection moulding, hollow areas in the mould are first closed and later reopened by using sliding cores or inserts.
For the production of a part consisting of two components, the first element of the piece is first injected in an initial injection phase, after which a second hollow area is opened by pulling a sliding core, for instance. Finally, the second component is injected against the first, whereby the complete component part is produced and can be removed from the mould in its final form.