The gas assist injection moulding
After mould closing, the plastic is injected to fill or nearly fill the mould cavity.
After a selected time delay, first phase is gas injected.
Second phase gas penetration to compensate for volumetric shrinkage of the plastic as it cools.
A uniform gas pressure is applied throughout the plastic.
Gas is exhausted to atmosphere or for recovery before mould opens.
Plastic refill commences after the nozzle valve is closed or after the plastic feed gate has solidified.
Gas Assist injection moulding advantages
Elimination of sink marks.
Avoidance of plastic packing from the moulding machine.
Reduced in-mould pressures by up to 60%, and therefore reduced press lock forces enabling larger
The use of the gas injection moulding as a means of transmitting pressure uniformly throughout the moulding.
mouldings on much smaller machines.
Reduced power consumption.
Introduction to the processing cycle of gas-assisted injection molding
Injection molding process
The quantitative plasticized plastic is filled into the cavity. The required amount of plastic is to be found through experiments to ensure that the gas does not break through the surface of the finished product during nitrogen filling and can have an ideal volume of nitrogen.
The gas may be injected at different times during or after the injection period, and the pressure of the gas injection must be greater than the injection pressure to achieve a hollow state.
Gas holding period---When the inside of the finished product is filled with gas, the pressure of the gas acting on the hollow part of the finished product becomes the holding pressure, which can greatly reduce the shrinkage and deformation rate of the finished product.
As the cooling cycle is completed, the gas pressure of the injection mold is reduced to atmospheric pressure, and the finished product is ejected from the cavity.
Remarks---With the requirements of different machine equipment and injection molding technology, the inflation period can be triggered by the screw stroke or contact.