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The basic process of injection moulding involves cooling the heated plastic, allowing the resin to set into the desired shape of the product being manufactured. This can be undertaken by running channels through the mould which extract heat, allowing the materials to cool. This process naturally causes the resin to shrink away from the surface which, if excessive, can cause issues with the quality control of the final product. In order to compensate for this, a larger amount of resin is pumped into the mould than is actually required for production, allowing the mould to shrink and all parameters to match the original specifications.

Gas Assisted Injection Moulding injects gas into the cavity of the mould during Internal Gas Assisted Moulding or around the outside surface of the mould during External Gas Assisted Moulding. Usually, the most common form of Gas Assisted Moulding is the Internal variety, with the External method used for improving the surface definition of the finished part.

How does it work? Inert gas is used in order to mitigate any risk of combustion during the moulding process – with this usually being Nitrogen. The basis for doing this, is that the gas acts as a natural ‘barrier’, allowing the shape of the part to be kept during cooling without the associated issues caused by shrinkage, such as warpage and deformation.

There are, of course, costs benefits to using Gas Assisted Moulding, with one of the main plus points being the reduced cycle times and lower wastage of parts that fail quality control checks due to excessive shrinkage. This negates the slightly higher cost of the initial production process and also allows a hollower and, therefore, lighter mould to be used initially, further reducing total per unit production costs.

In conclusion, it can be seen that there are many benefits to using Gas Assisted Moulding and if you would like to consider this technique for your next project, please discuss it with one of our experienced engineers today!