High-Pressure Die Casting
This casting process injects molten non-ferrous metal such as aluminum into the cavity of a mold – also known as a die – under very high pressure. The cavity, which will create the shape and details of the part, is produced using two hardened steel mold cavities which have been machined in the reverse image of the part.
The dies are prepared each cycle by spraying the mold cavity with lubricant, which helps control the temperature of the die and assists in the removal of the casting. The molten metal is then poured into a sleeve and injected into the mold with the use of a plunger connected to a hydraulic cylinder that operates at high speed and pressure. Once the mold is filled, the pressure is maintained until the casting solidifies. The dies are then opened, then the shot (which can be multiple castings) is ejected from the die. Since dies can be re-used multiple times, the process is repeated depending on how many final parts are needed. The type of metal being cast determines whether a hot-chamber or cold-chamber machine will be used. The cold chamber machine is normally used for aluminum alloys.
The casting equipment and metal dies require large capital costs, so this process is most appropriate for higher-volume production. While the equipment requires a significant investment, manufacturing of parts using this process is relatively simple and the die can last hundreds of thousands of cycles. This keeps the incremental cost per item low. High-pressure die casting is particularly well-suited for a large quantity of thin walled castings, from small-sized to large-sized, including parts which require greater detail and precision, near net final shape. This is why it’s the most used casting process. Die castings are characterized by a very good surface finish and dimensional consistency.