What is Mould Shrinkage?


Shrinkage is a characteristic of resin which occurs during plastic injection molding process. Different resins have different mold shrinkages. Crystalline and semi-crystalline materials exhibit higher shrinkage than amorphous materials. Unreinforced plastics have higher shrinkage than

reinforced grades. It is important that the grade of material be selected before the injection mold tooling is constructed and that the proper mold shrinkage be specified.


Mold shrinkage rate can vary with part and tool design: thick walls will have higher shrinkage rates than thin, variation in section thickness can cause differential shrinkage and warpage;flow direction will effect shrinkage,particularly with glass fiber-reinforced grades





Shrinkage in mould is also influenced by process conditions. As cavity pressure increases,shrinkage typically will decrease. The plastic injection mold and melt temperature will also influence shrinkage. Cooler molds will reduce shrinkage while hotter melt temperatures will increase shrinkage especially with semi-crystalline materials.


Contact HS Mold Company for shrinkage recommendations on any of plastic injection molded products. We are one of the leading plastic injection mold builders based in China.



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