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Shrinkage of raw plastic &. problems caused by it.
- Sep 09, 2017 -

Shrinkage  Of Raw Plastic

Causes of excessive part shrinkage 
Excessive shrinkage, beyond the acceptable level, can be caused by the following factors. The relationship of shrinkage to several processing parameters.

· low injection pressure

· short pack-hold time or cooling time

· high melt temperature

· high mold temperature

· low holding pressure.


Problems caused by part shrinkage. 
Uncompensated volumetric contraction leads to either 
sink marks or voids in the molding interior. Controlling part shrinkage is important in part, mold, and process designs, particularly in applications requiring tight tolerances. Shrinkage that leads to sink marks or voids can be reduced or eliminated by packing the cavity after filling. Also, the mold design should take shrinkage into account in order to conform to the part dimension. Part shrinkage predicted by C-MOLD offers a useful guideline for proper mold design.