In the process of injection mold, the quality of the finished product of the mold and whether the accuracy meets the requirements is the most important thing, the molding mold should meet the requirements of size, accuracy and shape, but the injection molding process will be inconsistent because of the difference in heat and shrinkage, so this process should be carefully handled.

Improper injection mold or design will directly affect the shrinkage rate of plastics, because the size of the plastic product plus the estimated size of the shrinkage rate obtained, and the shrinkage of the injection mold cavity is generated within the range of the numerical treatment or plastic recommended by plastic injection molding, which not only forms the injection mold, but involves the distribution, shape and orientation of the crystalline engineering plastic (anisotropy). Plastic product, size and distance to gate at gate position in relation to gate position. The role of plastic shrinkage is mainly heat resistance shrinkage, shrinkage phase, shrinkage direction, shrinkage of the compression coefficient of elastic recovery, and these factors and molding conditions or related items precision injection parts operating conditions.

Because injection molding is the process of changing the raw material from powder or another form, it will go through multiple steps, and it needs to melt and fuse at high temperature. In the case of mutual advancement of these steps, the resulting shape of the material will be changed, and all those who need to go through this step can affect the physical properties, size, quality and appearance.