Casting

Summary

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 materials are usually metals or various time setting materials that cure after mixing two or more components together; examples are epoxy, concrete, plaster and clay. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods. Heavy equipment like machine tool beds, ships' propellers, etc. can be cast easily in the required size, rather than fabricating by joining several small pieces. Casting is a 7,000-year-old process. The oldest surviving casting is a copper frog from 3200 BC. Throughout history, metal casting has been used to make tools, weapons, and religious objects. Metal casting history and development can be traced back to Southern Asia (China, India, Pakistan, etc). Southern Asia traditions and religions relied heavily on statue and relic castings. These items were frequently made from a copper alloy laced with lead. Since the beginning of metallurgy the majority of castings were simple one to two piece molds fashioned from either stone or ceramics. However, there is evidence of lost wax castings in numerous ancient civilizations. The lost wax process originated in ancient Mesopotamia. The earliest known record of lost-wax casting is a clay tablet written in cuneiform in the ancient city of Sparta, Babylon, which specifically records how much wax is needed to cast a key. The earliest-known castings in the global archaeological record were made in open stone molds. There are two types of lost wax methods, direct lost wax method and indirect lost wax method. The direct molding method is to make the wax material into the same wax mold as the casting by hand or other tools; the indirect molding method is to make the wax mold through the mold.