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A method developed by Shigeo Shingo to reduce changeover times (the time required to switch production equipment from one product to another) to less than ten minutes. The name refers to the goal of completing a changeover in a single-digit number of minutes: one through nine minutes, hence “single minute.”
Background
Japanese engineer Shigeo Shingo developed the fundamental insights behind SMED in the 1950s and 1960s, largely based on his work at Toyota and other Japanese manufacturers. His key breakthrough was a distinction that had rarely been explicitly made until then.
Internal versus External
Shingo distinguished between two types of changeover operations:
Internal operations can only be performed when the machine is at a standstill. For example, changing a die or reconfiguring a clamping setup.
External operations can be performed while the machine is still running. For example, preparing tools, preheating a mold, or retrieving materials.
In practice, these two types of operations were often performed interchangeably, resulting in unnecessarily long machine downtime.
1. Separate: Identify all changeover operations and clearly distinguish between internal and external ones.
2. Conversion: Convert as many internal operations as possible to external ones, so that they can take place while the machine is still in production. This is the step with the greatest impact on downtime.
3. Streamlining: Optimize the remaining steps. Consider standardizing fastening methods, using preset tools, or improving ergonomics and workstation layout.
Why SMED Is Central to Lean Long changeover times have traditionally been used to justify large production batches: the longer the changeover takes, the more you produce before the next changeover. SMED undermines that logic. When changeovers are fast and inexpensive, the need for large production runs disappears. This makes it possible to produce more frequently, in smaller batches, and based on actual customer demand—a prerequisite for flow and for reducing inventory as a form of waste.
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.)
Would you like to learn more about SMED (and other key Lean )? If so, we recommend our Lean Green Belt . SMED is a core component of our Lean Green Belt program.
