There are many factors for the shrinkage of injection molded parts after demoulding, mainly including the following factors.

Glass transition temperature

The lower the transition temperature of the glass-like material, the more obvious the shrinkage of the injection molded part after demoulding. If the glass transition temperature of the plastic is higher than room temperature, the shrinkage rate of the product made of this material is low after demolding because the molecular motion energy is insufficient. For materials whose glass transition temperature is much higher than room temperature, such as PEEK, there is basically no problem of shrinkage after demolding.

Fillers and Additives

For plastics with fillers added, the presence of fillers can prevent the shrinkage of injection molded products. Therefore, the more filler added to the material, the less it will shrink after demolding.

Product thickness

Plastic injection molding manufacturers also play an important role in mold release and shrinkage. In general, thicker parts of the part will retain more heat and therefore cause additional post-release shrinkage. This can also cause warpage, which is caused by uneven cooling of the part. If one area of a part cools, while a thicker part of the same part is still cooling and shrinking a bit, the thicker part will affect the thinner part and drive the part in the direction of shrinkage, deforming and warping the part .