Stack moulds belong to the group of multi-activity tools used in injection moulding machines. Just like tandem moulds, they have two or more mould parting surfaces. In contrast to tandem moulds, however, the moulded parts are injected into the mould cavities of the various layers in one procedure.
Stack moulds are especially suitable for flat moulded parts with thin wall thicknesses. Here, the mould's locking pressure determines the size of the injection moulding machine, whereas the opening stroke and the injection volume are of secondary importance. The machine can therefore hardly be used efficiently when using a standard mould. The stack construction multiplies the number of mould cavities and enables a considerable increase in productivity for a given machine size.
In injection moulding, for example, 2, 4 or 8 components can thus be produced per section. Thanks to the mould parting surfaces located opposite one another, the locking forces are halved.