Casting is a process in which molten metal is poured or injected into a cavity and allowed to solidify taking on the shape of the cavity. After solidification, the part is removed from the mold and then processed for delivery. Casting processes vary from simple to complex. Material and process selection depends on the part’s complexity, function, depends on the part’s complexity, function, quality specifications, and the projected cost level. Green-sand casting and shell molding are two processes where patterns can be used repeatedly. Shell molding offers a higher degree of accuracy and surface finish than sand casting, although it cannot match the accuracy of the permanent-mold process or the precision of investment-casting methods. There are some processes where both the pattern and mold can only be used once. Two of these are investment casting and evaporative (lost foam) casting. Two general types of metal injection mechanismsfor die-casting machines are the hot-chamber type and the cold-chamber type.