Single-Minute Exchange of Die (SMED) is a lean production method for reducing waste in a manufacturing process. It provides a rapid and efficient way of converting a manufacturing process from one product to the next. SMED is also often referred to as Quick Changeover (QCO). Performing faster changeovers is important in manufacturing, or any process, because they make low-cost, flexible operations possible.
The term “Single-Minute” refers to the objective of reducing startups and changeovers to single digit minutes (in other words, less than 10 minutes). The closely related yet more challenging concept of One-Touch Exchange of Die (OTED) states that changeovers can and should take less than 100 seconds.
SMED was developed in Japan during the 1950s and 1960s by industrial engineer Shigeo Shingo, to help Toyota and other manufacturing firms reduce costly inventories and improve efficiency. At the time, almost all changeover work was performed while machines were down (i.e. not running). Shigeo Shingo made a distinction between changeover work that occurs while a machine is down, Internal Setup, and preparatory work that can occur while a machine is running, called External Setup.
The SMED philosophy breaks setup down further, into four stages:
- In the preliminary stage there is no distinction between internal and external work, and all setup work is combined.
- In the second stage, external setup and internal setup are identified and separated.
- In the third stage, work that was previously included in the internal setup is transferred to external setup.
- The fourth stagespecifies continuous improvement of all internal and external setup work.
Shigeo Shingo’s data from between 1975 and 1985 documents reductions in changeover times averaging over 90%, for a range of manufacturing companies. However, SMED provides additional improvements that stem from a systematic examination of operations, including:
- A reduction in the footprint of processes, with reduced inventory freeing floor space
- Productivity increases/reduced production time
- Increased machine work rates from reduced setup times, even when the number of changeovers increases
- Reduced defect rates due to the elimination of setup errors and trial runs
- Improved quality stemming from fully regulated operating conditions
- Increased safety due to simpler setups
- Simplified housekeeping due to fewer tools and better organization
- Reduced setup expense
- Elimination of unusable stock from model changeovers and demand estimate errors