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What is Shrinkage and Warpage of Plastic
Mold shrinkage is the shrinkage of the polymer as it cools after the molding process. It is typically used to properly machine injection molds so that final part dimensions are as desired. Mold shrinkage can be Dependant upon the molding parameters used - often the extremes of the processing range for the material plus a midrange value are tested.
we can use standard test ASTM D955, ISO 294, ISO 2577 for shrinkage test methods, Part shrinkage may be thought of as a geometric reduction in the size of the part. If the shrinkage is uniform, the part does not deform and change its shape, it simply becomes smaller.

then what is warpage? , Warpage results when shrinkage is not uniform. If regions of the part shrink unequally, stresses are created within the part which, depending on part stiffness, may cause the part to deform or even crack in the long term. (moldflow.pte.ltd )

Relation Between Injection parameter setting and shrinkage
All mold engineer or plastic engineer know that shrinkage and consequently warpage is affected by processing conditions such us injection machine parameter setting.
picture below shown relation between shrinkage and injection machine parameter.

click the picture to enlarge