1、to understand the flow behavior of plastic melt, considering the flow of plastic flow in the flow channel and the cavity, the flow velocity and the maximum flow length. 2、taking into account the cooling process of plastic shrinkage and shrinkage problem. 3、to control the crystallization of plastic in the mold. 4、the choice of the feed point. 5、parts of the horizontal core pulling and the top of the problem. 6、die cooling or heating problem. 7、the relationship between the size of the mold and the injection machine, including the maximum injection amount of the injection machine, the clamping force.