SMED – Single Minute Exchange of Die

SMED is the acronym for Single Minute Exchange of Die and was invented by the Japanese Shigeo Shingō within the Toyota Production System (TPS). The focus at first was on the exchange of especial big, hardly to be used compression moulds but later it was applied in general to the exchange of tools.[1]

The basic idea of SMED is to accomplish as many steps as possible of the machine setup while it is working. This comprehensive approach leads to a considerable shortening of tool exchange and setup times. Through lowering these times the Single Minute Exchange of Die method provides the company with higher flexibility in the production. Therefore it’s possible to produce smaller batches and concurrently lower the costs and the lead time.[2]

The activities which have to be accomplished during a Single Minute Exchange of Die procedure are shown below:

Separating Internal and External Setup

The most important step by implementing SMED is distinguishing between internal and external setup.[3]

  • “Internal setup (IED), such as mounting or removing dies, that can be performed only when a machine is stopped”[4]
  • “External setup (OED), such as transporting old dies to storage or conveying new dies to the machine, that can be conducted while a machine is in operation”[5]

It is obvious that preparation of parts, maintenance and so forth should not be done while the machines are stopped. Nonetheless this is often the case. Thus mastering the distinction between internal and external setup is the passport to achieving SMED.

Converting Internal to External Setup

This stage can be divided into two important notions:

  • Re-examining operations to see whether any steps are wrongly assumed to be internal
  • Finding ways to convert these steps to external setup

Operations that are now performed as internal setup can often be converted to external setup by re-examining their true function. This requires the adoption of new perspectives which are not bound to old habits.[6]

Further improvements can be achieved with the implementation of standardisation into all setup processes, the introduction of quick releases, mechanisation and the parallelisation of setup processes.[7]

A passage which underscores the impact of setup time reductions on the improvement of production activities as a whole is given by Taiichi Ohno:

“Until some ten years ago, production in our firm took place as much as possible during regular working hours. Changes of cutters, drills and the like were relegated to the noon break or the evening. We had a policy of replacing the cutters after every fifty items. Yet as production has risen over the past decade or so, machine operators have often begrudged the time needed for these changes. For the multigrinder in particular, replacing the numerous cutters and drills took half a day. Since afternoon production would stop whenever a replacement was made on a weekday, workers were forced to work temporary shifts on the following Sunday. This was uneconomical and therefore unacceptable. Since we also wanted maintenance to be done during working hours, we began to study the question of how setup changes could be performed in a very short period of time. Shigeo Shingō, of the Japan Management Association, was advocating “single-minute setup changes” and we felt that this concept could be of great service to us. It used to be that after spending half a day on setup, the machine might be used for only ten minutes. Now, one might think that since the setup took half a day, production ought to continue for at least that long. This, however, would have left us with a lot of finished products we could never sell. We are now looking into cutting setup times down to a matter of seconds. Of course this is easier said than done. Somehow, thought, we must reduce the amount of time needed for setup changes.” [8]

[1] Kamiske, Brauer (2007), Qualitätsmanagement von A bis Z, p.299ff.

[2] Cf. Ibid.

[3] Shingō (1985), A Revolution in Manufacturing, p.29.

[4] Cf. Ibid, p.22.

[5] Shingō (1985), A Revolution in Manufacturing, p.22.

[6] Shingō (1985), A Revolution in Manufacturing, p.22. and Sheldon (2007), Lean Materials Planning and Execution, p.34.

[7] Kamiske, Brauer (2007), Qualitätsmanagement von A bis Z, p.300ff.

[8] Shingō (1985), A Revolution in Manufacturing, p.25f.


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