Switching production equipment from one type of part to another as quickly as possible. SMED refers to the goal of reducing changeover times to less than ten minutes. 

Shigeo Shingo's important insights on changeover time reduction, which he developed in the 1950s and 1960s, were that internal changeover operations - which can only be performed when a machine is idle (such as when a mold needs to be changed) - must be separated from external operations that can be performed while the machine is in operation (such as bringing the new mold to the machine). Then, as many internal changeover operations as possible should be turned into external operations. (Shingo 1985.)