Single-Minute Exchange of Die

Single-Minute Exchange of Die (SMED) is one of the many lean production methods for reducing waste in a manufacturing process. It provides a rapid and efficient way of converting a manufacturing process from running the current product to running the next product. This rapid changeover is key to reducing production lot sizes and thereby improving flow (Mura), reducing production loss and output variability.

The phrase "single minute" does not mean that all changeovers and startups should take only one minute, but that they should take less than 10 minutes (in other words, "single-digit minute"). Closely associated is a yet more difficult concept, One-Touch Exchange of Die, (OTED), which says changeovers can and should take less than 100 seconds. A die is a tool used in manufacturing. However SMED's utility of is not limited to manufacturing (see value stream mapping).

Frederick Taylor analyzed non-value-adding parts of setups in his 1911 book, Shop Management (page 171). However, he did not create any method or structured approach around it.

Frank Gilbreth studied and improved working processes in many different industries, from bricklaying to surgery. As part of his work, he also looked into changeovers. His book Motion Study (also from 1911) described approaches to reduce setup time.

Even Henry Ford’s factories were using some setup reduction techniques. In the 1915 publication Ford Methods and Ford Shops, setup reduction approaches were clearly described. However, these approaches never became mainstream. For most parts during the 20th century, the economic order quantity was the gold standard for lot sizing.

The JIT workflow of Toyota had this problem of tools changeover took between two and eight hours, Toyota could neither afford the lost production time nor the enormous lot sizes suggested by the economic order quantity. Lot reduction and set up time reduction had actually been ongoing in TPS since 1945 when Taiichi Ohno became manager of the machine shops in Toyota. On a trip to the US in 1955, Taiichi Ohno observed Danly stamping presses with rapid die change capability. Subsequently, Toyota bought multiple Danly presses for the Motomachi plant. And Toyota started to work on improving the changeover time of their presses. This was known as Quick Die Change, or QDC for short. They developed a structured approach based on a framework from the US World War II Training within Industry (TWI) program, called ECRS – Eliminate, Combine, Rearrange, and Simplify.

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