While plastic injection molds are required to have the functions for producing molded parts with the desired quality, at the same time it is also required that production be possible at the lowest possible production cost.

The cycle of plastic injection molding is defined as follows.

Among the factors determining the molding cycle, the one that is the most important is the cooling time t2. Cooling time is the time from filling the inside of the cavity with molten plastic to the sealing of the gate until the plastic solidifies. From experience, it is known that the cooling time varies depending on the cooling capacity of the cavity of the mold. In addition, it also varies depending on the type of molding material and the wall thickness of the molded product. Predicting what the optimum cooling time is during the mold design stage is a very important matter in estimating the production cost of the molded product. While recently software products have come on the market that predict the cooling time by CAE, in general, the following experimental equation is used for predicting the cooling time.