Die casting is the manufacturing process that makes geometrically complex metal parts, making use of molds that are reusable. These molds are called dies and the process involves a furnace, metal, die casting machine, and a die. Metals used in the die cast process are usually non-ferrous alloys, such as Zinc or Aluminum.
Die Casting Process Cycle
The die-casting process involves five different stages, but the total cycle time is short and will be between two seconds and a minute, typically. The various stages involved in the process are explained below.
Clamping
The first step in die-casting is the preparation and clamping of both halves of the die. Before clamping, each of the die halves is cleaned and lubricated properly. The lubrication time will increase with the size of parts, number of side cores, and cavities. Additionally, you may need to lubricate after each cycle, or after two or three cycles, depending on the material. The two halves are then attached inside the machine, and securely clamped and closed.
Injection
Molten metal, maintained at a set temperature is transferred to a chamber and then injected to the die. The transferring method will depend on the type of die casting machine. After transferring the molten metal, it is injected into the die at high pressures. This high pressure holds the molten metal in the die and the metal solidifies inside the die. The amount of metal that is injected into the die is referred to as shot.
Cooling
When the molten metal enters the die cavity, it will start to cool and solidify. When the complete cavity of the die is filled and the metal solidifies, the casting is formed. The die will not be opened before the stipulated cooling time, because the casting needs time to solidify properly. Cooling time of the molten metal is estimated considering various factors like thermodynamic properties of the metal, the complexity of the die, and the maximum wall thickness of the casting.
Ejection
After cooling time has passed, the die halves are opened and an ejection mechanism pushes the casting out of the die cavity. The ejection time can be determined by the size of the envelope of the casting. This time should include time for the casting to fall off the die.
Trimming
While cooling, the material in the channels of the die will attach to the casting. This metal, together with any flash, should be trimmed from the casting. This can be done by a trimming press or manually with a cutter or saw.