Newcomers to the world of plastic injection moulding are often met with a whole new vocabulary that can seem quite confusing and intimidating at times. That’s why we’ve compiled this three-part post of some of the more common terms to help ease some of that uncertainty.

Welcome to Part 2 of our post, where we look at some of the terms from C through to D


The part of the injection moulding machine that holds the part in place during the injection moulding process.

Cold slug

The first material to enter an injection mould. It’s called a cold slug because as it passes through the spruce orifice it is cooled below the effective moulding temperature.


A plastic compound which contains a high percentage of pigments, which is mixed in with the base resin to change the colour of the part/product.


This refers to the complete repeating sequence of operations required for injection moulding a part.


The momentary opening and closing of a mould during the early stages of the cycle to permit the escape of air or gas from the heated compound.


This occurs when the surface of a finished part separates. Strata or a fish-scale-type appearance may be visible where the layers are separated.


Weight per unit volume of a substance.

Differential cooling

This occurs when one area of the part cools at a different rate or when the mould is surfaces are at different temperatures.

Dimensional stability

This refers to the ability of a plastic part to retain the precise shape in which it was moulded.

Click here to read Part 3.

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