Die casting consists of three elements: alloy, the raw material, a die casting machine and die. It is a process to inject molten alloy (melt) into the die under high pressure, which is said to be the shortest one from the raw material to the product. On the die casting machine two die halves, fixed and movable, are mounted; when the injected melt solidifies quickly, the movable die opens and the casting is taken out. Since it enables a mass production of complex-configuration parts, having 1) precise dimension, 2) accurate finish, 3) fine surface and 4) excellent strength; its merit is highly evaluated, playing an important role in the metal processing industry.
Types of Die Casting Processes
The two die casting processes used industrially are hot chamber, and cold chamber dies casting. Each one has its peculiarities and is applicable in different scenarios.
The hot chamber die casting process is the perfect method for working with low melting point materials such as zinc, tin, lead, and magnesium alloys. It is not suitable for alloys with a higher melting point as it would damage the pump as the pump would directly contact the metal. It involves melting the metal and injecting it into the die using pressure from a hydraulic system.
The cold chamber die casting is the perfect method for working with high melting point materials such as aluminum. This process is ideal for such metal as the high temperature needed to melt the material can damage the pumping system.
The process involves ladling the melted material into a cold chamber before injection into the die. The hydraulic system used in a cold chamber process is similar to that of the hot chamber process. However, it might require a larger pressure ranging from 2000 to 20000 psi.
Steps of Die Casting Process
Whether hot or cold chamber die casting, the standard process involves injecting molten metal into a die mold under high pressure. Below are the intricate die casting process steps:
The first step in the die casting is clamping. However, before then, clean the die to remove any impurities and lubricate the die for better injection and removal of the solidified product. After cleaning and lubrication, clamp and close the die with high pressure.
Melt the metal you want to inject and pour into the shot chamber. The procedure depends on the process you are using. For example, the shot chamber is cold in the cold chamber die casting, while it is hot for the hot chamber die casting. After that, inject the metal into the die under high pressure generated by a hydraulic system.
While clamped, allow the metal to cool for solidification. The solidified material will have a shape similar to the design of the mold.
After unclamping the die mold, an ejection mechanism will push the solid casting out of the die. Ensure proper solidification before ejecting the final product.
This is the final step, and it involves the removal of the excess metal in the sprue and runner found on the finished product. Trimming is achievable using a trim die, saw, or other procedures. The removed metal parts are recyclable and reusable in the process.