1. understand the plastic melt flow behavior, considering the resistance of plastics in runners and cavities of each flow velocity, check the maximum flow length. According to the plastic flow direction in the mold (namely filling order), consider re plastic in the mold cavity and the fusion of the original air export problem. 2. the problem of shrinkage and shrinkage of plastic during cooling is considered. 3. the mold is designed to control the crystallization of the plastic in the mold. The orientation and improvement of the internal stress of the product. 4. the choice of the typing surface. The problem of horizontal core pulling and ejecting of 5. parts. 6. the cooling or heating of the mold. 7. the relationship between the size of the mold and the injection machine used, including the maximum injection amount, the clamping force, the size of the mold part and so on.