The Die Casting Process

The die casting process involves the following four steps:

Step 1: Melting the Metal

First, the metal to be used is melted in a heated cauldron. The cauldron may be located inside the equipment in a hot chamber casting process or outside the equipment in a cold chamber casting process. Since the process is continuous, a constant supply of molten metal is required, so metal must be added to the melt during production.

Step 2: Measuring the Shot and Preparing the Mold

Next, a precise and predetermined amount of molten metal is drawn into a "shot" or pressure chamber. This shot or amount of metal is then injected into the mold.

The mold itself (or die) consists of two halves: the cover mold and the ejector mold. The cover mold (one half of the mold) is held in place by a stationary platen, which is a heavy, non-movable steel block that holds the cover mold in place during the casting process. The ejector mold (the other half of the mold) is mounted on a movable platen that slides back and forth. This half of the mold contains a hole through which the molten metal is injected.

Step 3: Close the mold and inject metal

To start the molding cycle, the mobile platen holding the ejector mold slides forward and presses against the cover mold. The two mold halves are then brought together under high pressure—up to 1,900 tons.

As the two halves of the mold are squeezed together, the molten metal in the shot chamber is injected into the mold with tremendous force. This step must be done quickly to prevent the cast metal from solidifying before the mold is filled.

Step 4: Open the mold and remove the casting

The platens press the two halves of the mold together until the metal solidifies. Once the casting is in a solid state, the movable platens retract, taking the ejector half of the mold away with the finished product.

A clamp (usually a robot) holds the finished part, while the ejector pins on the ejector half of the mold push the finished part out of the mold. The part is then held in place while excess material (called flash and sprues) is removed. In many cases, this excess material can be remelted and reused. The part then moves to the finishing stage.