Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods. Common casting materials include metals and various thermosetting and thermoplastic polymer resins.
Casting processes have been developed over thousands of years for manufacturing parts of various sizes. Metal molds have of course evolved along with humans’ understanding of metallurgy and production technology. Examples of casting processes used in the industry include green sand casting, investment casting, die casting, permanent mold casting, and centrifugal casting.
Green sand casting is the most common form of casting, in which sand is held in a mold with a pattern to create the desired shape. The sand is then soaked with specialbinders, such as resin, sodium silicate, or bentonite, and activated by heat or water to create the desired shape.
Investment casting is one of the most sophisticated casting methods. It is done by first making a wax pattern, which is sprued, burned out, and then filled with a ceramic slurry. When the slurry hardens, the wax is melted or boiled away and the metal is poured into the remaining cavity. This is a very accurate process, but is limited due to its labor intensity and relatively high cost.
Die casting processes involve forcing molten metal under high pressure into a mold cavity. The mold is usually machined into two halves made out of steel, aluminum, or iron. The molten metal is injected into the mold at a pressure of 10-210 MPa. This type of casting is usually limited to non-ferrous metals.
Permanent mold casting involves the use of metal molds that produce metal parts that can be used in both high and low volume production. The metal molds are typically made out of cast iron, steel, or aluminum and can be used over and over again to create the same metal parts.
Centrifugal casting is used to produce hollow parts. It involves pouring molten metal into a spinning mold which causes the metal to be evenly distributed throughout the mold. This is a very effective process for creating hollow parts with a uniform wall thickness.
Casting is an important manufacturing process because it allows manufacturers to produce parts with complex shapes that would otherwise be difficult or impossible to make using conventional methods. It is also one of the oldest and most widely used processes in metal processing because of its effectiveness and relative ease.
