Injection mold shrinkage

Injection mold shrinkage has always been an important part of mold development. This has a huge impact on the size of the plastic. After the mold structure is determined, each part of the mold can be designed in detail, that is, the size of each template and part, the size of the cavity and core, etc. At this time, major design parameters such as material shrinkage will be involved. Therefore, the size of each part of the cavity can only be determined by specifically grasping the shrinkage rate of the molded plastic.

The shrinkage rate of different plastics is different. For example, PP, the shrinkage rate is between 1-2.5, which is better, some PP even reaches about 5, the larger the shrinkage rate proves that the plastic is very soft and feels very good.

For example, nylon, the search rate of this material is between 0.3-1. The product strength is very high. It feels very hard, nylon is mainly used in various machinery, and the accuracy of the product will be very high.

Because the shrinkage rate still affects the deformation of the product. The higher the shrinkage of the product, the greater deformation the product will have. During production, we must take good care of the structure of the product or check the deformation of the product and make appropriate adjustments to ensure the appearance and size requirements of the product.

For example, for the wall thickness of the formed part, the cooling time of the thick wall is generally longer, so the shrinkage rate is also larger. Therefore, we must moderate the wall thickness of the product, and the pressure loss of the part away from the gate is large. So the shrinkage rate of the plastic at this place is also greater than that near the gate. Shapes such as ribs, holes, bosses and carvings have shrinkage resistance, so the shrinkage rate of these parts is small. It can be adjusted appropriately to reduce product distortion.