Low-Pressure Casting
Low-pressure casting is a casting process that uses a combination of static and dynamic forces, such as pressure, time, and temperature, to shape solidified metal into desired shapes. The process most often utilized with aluminum, but can be used with other alloys such as magnesium, brass, and bronze. It is usually used to produce components in high volume with consistency and accurate dimensions.
The low-pressure casting process begins with the creation of a mold. Steel or ceramic molds are commonly used and consist of two parts: a cope and a drag. The drag is the top portion of the mold and the cope is the bottom. The two molds come together before molten metal is poured into the space between them. Pressure is then applied to push the molten metal into the “fill” part of the mold.
The pressure is generated by a pressure-vacuum system fed from a chamber filled with a low-boiling point liquid. This liquid is pumped up to the chamber, generating pressure in the casting chamber, which pushes the molten metal into the mold. The pressure continues to build, compressing the metal and creating a uniform distribution of air gaps and cast shapes.
Once the metal has been poured and under pressure for a specified time, the pressure is gradually released and the molten metal is then allowed to cool and solidify into its final shape. The mold is opened and the parts are removed from the completed casting. Additional processes, such as shot-peening, can also be employed to produce additional strength and improve surface finish.
Low-pressure casting offers many advantages over traditional casting methods. Its quick and repeated production capabilities result in shorter cycle times and lower unit costs, while its use of pressure ensures consistent quality and improved mechanical properties. Low-pressure casting also eliminates the need for machining of the casting, and produces components with good dimensional accuracy and high core strength.
Low-pressure casting is the ideal process for mass production of parts with exacting dimensional requirements. It is used extensively in the automotive and aerospace industries, and is becoming increasingly common in other industries, such as consumer products and medical equipment. With its consistent quality, accurate dimensions, and cost savings, low-pressure casting has become an industry standard for efficient production.
