Die Casting Processes
The hot-chamber die casting process is only used for zinc and other low-melting-point alloys that do not readily attack and erode metal pots, cylinders and plungers. Development of this technology, through the use of advanced materials, allows this process to be used for some magnesium alloys. The basic components of a hot-chamber die casting machine and die are illustrated below.
During the hot-chamber process, the plunger and cylinder, which constitute the injection mechanism, are submerged in the molten metal in the crucible (or pot), which is integral to the machine. The operation sequence for the hot-chamber cycle is illustrated below.
Operating Sequence of the Hot-Chamber Die Casting Process
- The die is closed and the piston rises, opening the port and allowing molten metal to fill the cylinder.
- The plunger moves down and seals the port pushing the molten metal through the gooseneck and nozzle into the die cavity, where it is held under pressure until it solidifies.
- The die opens and the cores, if any, retract. The casting remains in only one die half, the ejector side. The plunger returns, allowing residual molten metal to flow back through the nozzle and gooseneck.
- Ejector pins push the casting out of the ejector die. As the plunger uncovers the filling hole, molten metal flows through the inlet to refill the gooseneck, as in step (1).