In the process of plastic mold processing, if various parameters cannot be well controlled, plastic products will easily shrink after shaping, which will affect the accuracy of plastic processing.

In the process of plastic mold processing, if various parameters cannot be well controlled, plastic products will easily shrink after shaping, which will affect the accuracy of plastic processing. So, what adverse effects will shrinkage have on plastic processing? Let us understand together.

1. Shrinkage after processing:

Plastic shrinkage can be divided into two types: molding shrinkage and shrinkage after processing. The shrinkage after processing is the shrinkage of the product within a period of time after demolding. Compared with the molding shrinkage, the post shrinkage is generally smaller. The first cause of post-shrinkage is the relaxation of the internal stress of the product. For polymers with rigid molecular chains, the post-shrinkage of the product is relatively large; this is mainly due to the slow movement of rigid molecular chains, and the transformation of the molecular chains from one state to another requires a long time to rearrange Therefore, the post-shrinkage time is relatively long, and the post-shrinkage rate is relatively large. On the other hand, rigid molecular chains are prone to internal stress and will gradually undergo stress relaxation after molding. The second cause of post-shrinkage is continued crystallization. For crystalline polymers, when plastics are processed and molded, they have not reached complete crystallization, and they can continue to crystallize at room temperature, causing slight shrinkage of products.

2. Average shrinkage rate:

Since the shrinkage of plastic injection processing is greatly affected by the molding conditions, the shrinkage rate is not a fixed value, but a range. In the specific processing process, various processing conditions can increase the molding shrinkage rate, you can choose 4 % Is the specific shrinkage rate; if the specific molding conditions are conducive to the reduction of the molding shrinkage rate, 2.5% can be selected as the specific shrinkage rate. Of course, the latter selection method is more difficult.