During the die-casting process of aluminum alloy die-casting machine, only one speed of the pressure-feed metal liquid enters its mold, and its injection speed is only 1m ~ 2m / s during operation. With this process, there are many internal pores in the casting, and the structure is loose. It was soon improved to a two-stage injection. The injection process was simply decomposed into two stages, slow and fast, but the fast speed was only 3m / s. Increasing the compactness of the die-casting parts, and adding a stage of pressure increase after slow and fast, become three stages of slow injection, fast injection and promotion, which is the classic three-stage injection.
