Die Casting

Die casting is a high-pressure, high-speed metal forming process. Its core principle is to inject liquid or semi-liquid metal into a precision mold cavity at extremely high speed under high pressure, and solidify it under pressure. The die casting machine is the core equipment that realizes this process. Through a set of precision mechanical, hydraulic, and electrical systems, it efficiently transforms molten metal into metal parts with complex shapes and precise dimensions.

The die casting machine mainly consists of four core parts: the clamping mechanism, the injection mechanism, the hydraulic system, and the electrical control system. The complete cycle of manufacturing a metal part begins with mold clamping. The clamping mechanism drives the moving platen toward the fixed platen, bringing the mold halves tightly together, and provides sufficient clamping force to ensure that the mold is not forced open during high-pressure injection. The clamping force is the primary parameter for measuring the size of a die casting machine, ranging from dozens of tons to several thousand tons, determining the maximum projected area of castings the machine can produce.

Once the mold is locked, the preparation and delivery of molten metal differ fundamentally depending on the type of die casting machine.

1. In a hot chamber die casting machine, the injection chamber is integrated with the melting furnace, and the injection plunger is directly immersed in the molten metal. The metal can flow into the chamber automatically without external pouring, resulting in an extremely fast cycle. However, this type is only suitable for low-melting-point alloys such as zinc alloys; otherwise, the high temperature would quickly corrode the injection components.

2. A cold chamber die casting machine separates the injection chamber from the melting furnace. Before each injection, a robotic arm or manual labor is required to scoop a measured amount of molten metal from the furnace into the chamber. This structure avoids prolonged thermal erosion of the injection mechanism by high-temperature molten metal, making it suitable for high-melting-point alloys such as aluminum and magnesium alloys.

The injection plunger pushes the molten metal in the chamber through the gating system and into the mold cavity at high speed. The high-pressure, high-speed characteristics enable die casting to produce precision parts with extremely complex shapes and very thin wall sections. After the molten metal fills the cavity, the injection plunger continues to maintain a certain pressure, which is the holding pressure phase. The purpose of holding pressure is to compensate for the volumetric shrinkage that occurs during solidification, thereby effectively improving the internal density of the casting and eliminating shrinkage porosity and voids.

However, the casting taken out of the die casting machine is not yet ready for direct delivery and use; it still requires post-processing steps such as removing gates, biscuits, and flash. Modern fully automated die casting cells have integrated part-taking robots, degating machines, conveyor belts, and other equipment. The removed biscuits can be automatically returned to the furnace for re-melting, achieving fully automated closed-loop production.