The design of plastic mold mold before the ball is mainly to plastic ball mold cavity size calculation, as everyone knows, plastic ball other plastic products, products from the mold out after cooling, the actual measurement of the size of plastic balls and other plastic products is smaller than the size of the mold cavity, the original is mainly plastic products shrink, plastic products and other products have the same physical characteristics of a thermal expansion and contraction, so the shrinkage of plastic ball mold cavity size set must be reference to design of plastic raw materials, plastic raw materials and different shrinkage rate of water is not the same as the most common plastic shrinkage is about 1000 5, but like PP POM plastic ball, plastic ball, plastic ball theory PA shrinkage rate is 15/1000 to 20/1000, so the plastic mold ball point size design To fully consider the production of plastic ball is what raw materials, then according to the shrinkage of raw material to design the plastic ball cavity size, there is a need to pay attention to is that ordinary small plastic ball is below 6mm plastic ball can shrinkage with reference to the production of plastic raw materials to the design of plastic ball ball mold. But if you want to produce plastic ball diameter 6mm, it should consider increasing the cavity size, because the characteristics of plastic products is a gum thicker, shrinkage is bigger, if when the production of more than 12mm of plastic ball design of the cavity size, shrinkage rate than plastic shrinkage increase more than doubled, is the actual needs of the mold cavity size.