It’s important to have some adhesion so the part is properly formed; however a part sticking too long to the mould wall can be damaged or ruined so it needs to separate easily from the mould at exactly the right.
Types of releases include permanent systems that are added to the mould by specially treating it reactive & conventional chemical systems and hybrid systems.
Release systems may work for only one cycle or for many cycles at a time and they can affect the shrinkage rate of the part and the quality of the finish. Release agents build up over time and the rate of the build-up depends on the type of release being used. Moulds need to be regularly cleaned to remove all trace of build up when using temporary systems.