Bi-Injection is the simplest variant of two-component injection moulding from a machine and mould point of view: The two colours of the same plastic material are injected into a cavity via two independent gates to meet in the cavity in a more or less defined configuration.
When the mould closes, both units start filling the cavity. The position of the border line between the colours can be defined through different worm speeds. When entering similar volume flow rates [cm³/s], it is very easy with Sumitomo (SHI) Demag machines to adjust symmetrical filling of the mould with different worm diameters.
Low mould costs
Straightforward process engineering
This technique is preferably used for two purposes:
On the one hand, for parts intended to pass on some kind of information to the user via their two colours.
On the other hand, in automotive engineering where two colours are injected, which are to be transformed into some filigree pictograms later on, and these components are then to be over-coated and the pictograms are to be laser-engraved.