SMED — quick changeover between production orders
How to deliver quality to the customer every time
When a machine must switch from one production order to the next—new tools, new setup, new materials—production typically stops. That time is called setup time, and one of the most common methods to shorten it is called SMED, Single Minute Exchange of Die. The method was developed by Japanese engineer Shigeo Shingo, who showed that changeovers that normally took several hours could be cut to just a few minutes.
§What does the name mean?
"Single minute" does not mean that every changeover must take exactly one minute — it means changeover time should be reduced to a single-digit minute figure, i.e. under 10 minutes. The target is not always achievable for every machine, but the principle of the method is widely used to significantly reduce changeover time, often by around 20-40 percent with good SMED effort.
§Internal and external activities
The core of SMED is to distinguish between internal activities that can only be performed while the machine is stopped and external activities that can be prepared or completed while the machine is still running. By moving as much as possible from internal to external time — for example by getting tools, materials and instructions ready in advance — downtime can often be halved without changing the work itself.
- 01Internal activity: tool change in the machine while it's at a standstill
- 02External activity: fetch the next tool and material while the machine still runs the previous order.
- 03External activity: prepare and check the new tool before the machine stops.
- 04Internal activity: setup and trial run, which can only occur when the machine is ready for the new order
§Your role as a producer during a transition
As a manufacturer you are often the one who performs the changeover and your preparation has a direct impact on how long it takes. By having tools materials and a clear checklist ready before the machine stops you directly contribute to moving time from internal to external — and thus to shorter downtime and more production time.
| Before SMED thinking | With SMED thinking |
|---|---|
| Tool is fetched after the machine is stopped | Tool is retrieved and prepared before the machine is stopped |
| Errors and missing parts are discovered during changeover | Parts and instructions are checked beforehand |
| The transition time varies greatly from time to time | The transition follows a fixed, practised sequence |
§Why it matters for production
Shorter changeover time gives more flexibility: the company can run smaller batches without losing much time to changeover, making it easier to keep up with changing orders and customer wishes. For you as a producer, a good changeover routine also means less stress and fewer surprises, because the process is familiar and practiced.
“The time the machine stands idle to change over is time when nothing is being produced — that is why changeover time is one of the first things lean work directs its attention to.”