CINPRES Gas Injection, represented in Australia by HBM Plastics Technologies , has tested the effectiveness of external gas moulding (EGM) for the removal of stress in plastic moulded parts.
When applying the film of gas between the mould and plastic surfaces EGM enables pressure to be applied more uniformly throughout the moulding. It prevents lamina flow and virtually eliminates moulded stress.
EGM is based on applying gas pressure via a micro-thin film of gas on one surface of the in-mould plastic in order to force the plastic against the opposite "A" surface while cooling. This improves the replication of the A surface. Sink marks and other blemishes can be eliminated along with moulded in stress.