Single Minute Exchange of Die (SMED)
SMED was developed by Shigeo Shingo in Japan in the sixties and early seventies at Toyota and other Japanese firms. The impetus was to reduce costly inventories and improve efficiency.
An important foundation to the SMED system is the distinction between changeover work that occurs while the machine is not running, called Internal Setup, and preparatory work that occurs while the machine is running, called External Setup. At the point in time when SMED was developed, almost all changeover work was performed while the machine (press) was down.
The SMED philosophy breaks down into four stages:
1.In the preliminary stage, all setup work is combined. There is no distinction between internal and external work.
2.In the second stage, external setup and internal setup are identified and separated.
3.In the third stage, work that was previously included in the internal setup is transferred to external setup.
4.The fourth stage requires relentless and continuous improvement of all work elements within the internal and external setup (Kaizen).
A useful comparison is the pit crew of a racing team changing tires.
If the tools and parts are not prepared until the car enters the pit, then the pit stop will be lengthy. If the parts and tools are prepared beforehand (External Setup), the crew's every move is choreographed for efficiency, and special tools and fittings are used to increase speed, then the pit stop will be short.