SMED: Quick changeover for maximum flexibility

SMED stands for Single Minute Exchange of Die, a Lean that focuses on minimizing the time required to convert production equipment from one product to another. The goal is to reduce these changeover times to less than ten minutes (hence "single minute").

The core of the SMED method

Japanese engineer Shigeo Shingo developed the fundamental insights behind SMED in the 1950s and 1960s. His most important breakthrough was the distinction between two types of redirection operations:

1. Internal changeovers: Tasks that can only be performed when the machine is stationary (for example, changing a die).
2. External changeovers: Tasks that can be performed while the machine is still in operation (for example, preparing the new tools).

The SMED strategy consists of the following steps:

1. Separate: Identify and separate internal from external operations.
2. Convert: Convert as many internal operations as possible to external operations so that they can be done in advance while the machine is still producing.
3. Streamline: Optimize and simplify both internal and external operations that remain.

This approach drastically reduces changeover times. Not only does this increase productivity, but it also allows small batches to be produced more frequently, significantly increasing flexibility and the ability to respond quickly to customer requests.

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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.)