To compensate the shrinkage, it is necessary to inject more material after 100% filling of the part.
The length of packing time (green line in the time-pressure diagram below) must be selected in such a way that the gate freeze time is reached.
A short packing time leads to a higher risk of sink marks and voids.
Similar things will happen, if there is still molten material within the part but the gate is already frozen.
Injection Molding Process: The packing time is the time between 100% filling and gate freeze time.
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This glossary of plastic industry is provided by PLEXPERT Canada Inc.
