What is SMED?
SMED (Single-Minute Exchange of Die), also called quick changeover, is a method to reduce the time a machine stands still between the last good part of one product and the first good part of the next. Shigeo Shingo developed it in the 1950s and 1960s, cutting die changes on large presses from hours to minutes. Short changeovers are the key to small batches, low inventory and levelled production, and they directly raise OEE.
The SMED stages
| Stage | What you do | Typical gain |
|---|---|---|
| 0. Observe | Record the current changeover step by step, with times (video helps) | Baseline |
| 1. Separate | Identify which elements are internal and which can be external | 30–50% |
| 2. Convert | Move internal work outside the stop: preparation, preheating, staging | Further 10–30% |
| 3. Streamline | Speed up what remains: quick clamps, no adjustments, parallel work | Down to single minutes |
| 4. Standardize | Write the new method as standard work and train every team | Holds the gain |
SMED example: press die change
A press die change takes 111 minutes with the press stopped. Finding the die and tools, bringing the die to the press and returning the old die can all be done while the press is running (converted to external). Hydraulic quick clamps replace eight bolts, locating pins and standard heights remove most of the alignment and trial hits, a go/no-go gauge speeds up first-piece inspection, and scanning the die in the MES eliminates the paperwork. The machine-stopped time falls to 31 minutes, 72% shorter. With ten changeovers a week, that frees about 13 hours of press time every week.
Practical SMED ideas
- Prepare everything first: a changeover cart with the die, tools and checklist, ready before the stop.
- Replace bolts: quick clamps, cam locks, one-turn fasteners or U-slots.
- Eliminate adjustments: locating pins, standard die heights, preset settings and stops.
- Work in parallel: two people with a clear sequence often halve internal time.
- Make it visual: colour-code tools and settings per product; error-proof with poka-yoke.
How to use this SMED tool
- Record the changeover. Film or observe a changeover and list every element in order with its duration in minutes.
- Separate internal and external. Mark each element as internal (machine stopped) or external (machine running).
- Choose improvements. Click an element and choose: convert to external, streamline (with the new time), eliminate or keep.
- Compare before and after. The timeline shows the machine-stopped time before and after, with the reduction and the machine hours freed per week.
- Record the ideas. Write how each improvement will be made (quick clamps, preset heights, cart, checklist).
- Export. Export the SMED analysis to PDF, PNG or Excel for the kaizen event or the changeover standard.
Frequently asked questions
What is SMED?
SMED (Single-Minute Exchange of Die) is a lean method for cutting changeover time, developed by Shigeo Shingo at Toyota. The goal is a changeover in single-digit minutes (under 10). It works by separating internal work (done with the machine stopped) from external work (done while it runs), converting internal work to external, and streamlining everything that remains.
What is the difference between internal and external setup?
Internal setup can only be done when the machine is stopped, such as removing and mounting a die. External setup can be done while the machine is still running the previous job or already running the next, such as fetching tools, preheating the die or filling in paperwork.
What are the steps of SMED?
1 Observe and record the current changeover with times. 2 Separate internal and external elements. 3 Convert internal elements to external where possible. 4 Streamline the remaining internal elements (quick clamps, standard heights, parallel work, no adjustments). 5 Streamline external elements. 6 Standardize the new method and train.
How is changeover time measured?
Changeover time runs from the last good part of the previous product to the first good part of the next one, at full speed. It includes setup, adjustment, trial runs and first-piece inspection, not only the mechanical die change.
What are the benefits of SMED?
Shorter changeovers free machine capacity (higher OEE), allow smaller batches and more frequent changeovers, which cut inventory and lead time and make production levelling (heijunka) possible. They also make changeovers safer and more repeatable.
What are typical SMED improvements?
Preparing tools and the next die before stopping, quick-release clamps instead of bolts, locating pins and standard die heights to remove adjustments, preset settings, intermediate jigs, parallel work by two people, and checklists so nothing is forgotten.