During injection, compressed nitrogen is introduced into the cavity, which displaces the plastic core, creating a hollow area and ensuring optimum distribution of the material. The internal gas pressure usually ranges from 100 to 300 bar, but pressures of up to 450 bar are also possible. To avoid the melt flow of the plastic material coming to a standstill, gas and plastic are injected simultaneously into the cavity for a certain period of time. The holding pressure is controlled by the pressure profile set on the GIT unit.
A homogeneously prepared melt and a precisely operating injection moulding machine are important factors in the process. An activation of several injector modules is also possible to allow a simultaneous gas injection into individual cavities if multi-cavity moulds are used.

In comparison to GIT, displacement of the molten plastic is performed by the medium water, which is universally available at low cost, is reusable and also ensures effective cooling.

Gas injection moulding primarily allows material savings, since 20 to 30 % of the plastic material can be replaced by gas. Faster cooling of the moulded part and consequently shorter cycle times are achieved through a reduction in the wall thickness of the part and distortion is minimised as well as shrinkage reduced through more even pressure conditions in the cooling phase. Furthermore, GIT parts excel as a result of the improved weight/strength ratio of the moulded part. They also have a much higher surface quality than foamed parts.
With water injection technology, the cooling time can be reduced by up to 70 percent compared to GIT. Large parts with thin wall thicknesses and smooth surfaces on the inside of the part can also be realised using WIT. This process thus represents an attractive alternative and extension to gas injection moulding.