Imagine putting on the suit you last wore to a wedding after a long time. You notice that the trousers have been looser in the past, but buying a new suit is out of the question for you. You pull your stomach in a little, fasten the trousers and think: "I'll be fine for a few hours, just don't move (too much), then I'll be able to cope with the slight pressure around my stomach. You'll look good in the suit.
During injection moulding, the hot plastic is injected very quickly into the cooled tool geometry of the subsequent plastic moulded part. Then comes the big shock: cooling! The material, which has just been quick-fixed, solidifies with fright during the movement and everything quickly becomes too tight due to the onset of shrinkage. With Reprint and holding pressure the missing plastic molecules are pressed into the mould. When there is no more movement, the component is demoulded and looks good on the outside despite the frozen internal stresses.
Everything looks good on the outside for both components and people. But inside, the mood is oppressively bad. Finally out of your trousers - what a relief. If the component is later subjected to stress, heated or comes into contact with certain chemical agents, these hidden, frozen tensions can be released. The part is then deformed, it gets Stress cracks or breaks.