INTERNAL GAS PRESSURE

Plastic components should be designed in such a way that mass accumulations are avoided. Sometimes this is due to the Component geometry not possible.

Here, the internal gas pressure technology known as GID or GIT can counteract this. Airmould is also a common name.

With gas injection technology, thick-walled areas in the component are blown free with nitrogen; this results in normal wall thicknesses. Sink marks are reduced or avoided. In addition, the component is lighter, stiffer and can be produced in shorter cycle times.

Essentially, a distinction must be made between the displacement technique, blow-out technique and blow-back technique.

The displacement technique is the most resource-saving variant.

Here the component is only partially filled with plastic. Immediately after injection, gassing takes place in the thick-walled area. The plastic that is displaced here fills the remaining cavity with plastic. The advantage is that there is no plastic as an overflow/waste piece. The disadvantages are possible markings on the component due to stagnation of the melt at the flow front and a limitation of the

"After pressure" because this can only be done by the internal gas pressure.

With blow-out technology, the component is manufactured as in a classic injection molding process. After a necessary holding pressure time, a secondary cavity is opened and gas is applied to the thick-walled area. The plastic from the plastic core is pressed into the secondary cavity by the introduced nitrogen. This creates a component with the desired advantages and low wall thicknesses.

The blow-out technology can be expanded with the option of gas cooling or gas flushing. For this purpose, the introduced nitrogen is constantly flushed while maintaining the necessary back pressure. As a result, the component is additionally cooled by the gas core, which shortens the cycle time.

The blowback technique is only secondary. Here the melt is transported through the hot runner into the Screw antechamber pushed back.

In the event of gas counter-pressure, nitrogen is introduced at the rear of heavily ribbed components. This compensates for the gas that usually occurs on the back and the plastic is pressed homogeneously against the cavity on the side of the bowl for even temperature dissipation.

This technology is mostly used in our tools for complex exterior mirror housings or door handles.