Often, air or gasses are produced during the injection moulding process that must not be trapped in the cavity under any circumstances. Otherwise, cavities are created which are detrimental to the moulded part. To avoid quality defects in the plastic part, the excess air must be released from the closed system.
Sufficient venting has always been considered one of the demanding tasks in plastic injection moulding. Traditionally, this requirement has been met with ground surfaces on the ejector pin, for example. This undoubtedly achieves satisfactory results with regard to venting – but other risks such as burr formation or poorer guiding behaviour and thus significantly more wear have to be accepted.