SMED

In Production control, SMED is the abbreviation of English Single Minute Exchange off Die , literally “change of stamping tool in one minute”, expression which is generally translated into French by “fast change of tool”. With a little more precision individual minute corresponds to a time whose order of magnitude is the minute (either of a few minutes). This method was developed by Shigeo Shingo on behalf of the company Toyota.

Method SMED is used within the framework of changes of manufacture. It aims to reduce these times, and to thus make it possible to reduce the minimal size of batch. Indeed, if times of change of series become null, one can then consider a manufacture with the unit without increasing the costs.

During a change of manufacture, the part warming-up (MET) can represent a big part in manufacture. And the part warming-up is not productive. The goal is to decrease this time devoted to the adjustment, in order to obtain fast changes of tools or instantaneous adjustments.

One distinguishes two types of adjustment:

internal Adjustments/time : they correspond to operations which are made stopped machine, therefore except production.
external Adjustments/time : they correspond to operations which are made (or can be done) machine under operation, therefore in production.

The method proceeds in four stages.

Internal and external adjustments

It is a preliminary stage.

In the traditional adjustments, the internal and external adjustments are mixed: what could be made into external is made in internal adjustments. It is necessary to study the real conditions of the workshop in detail. A continuous analysis of production with a stop watch is a good approach. A more effective approach still is to use one or more video cameras, whose bands could be analyzed in the presence of the operators themselves.

It is necessary to identify the operations during the change of production:

preparation of the machine, the work station, the tools;
the checking of the matter and the measuring instruments;
disassembling/assembly of the tools;
adjustments of the dimensions of manufacture;
the realization and the control of the parts of test;
cleaning;
arrangement of the work station…

Separation of the internal adjustments and the external adjustments

It is the most important stage. Internal adjustments (or " time propres") are the operations which require obligatorily a stop of production (for example a change of tool). External adjustments (or " time externes") the operations gather which can take place during the production such (for example preparation of the tools and tools, presettings, or pre-heating, arrangement of the tools).

Transformation of internal adjustments into external adjustments

It is the second stage of the method.

The goal is to transform the internal adjustments into external adjustments. For example: pre-heating, préassemblage, use of a Bench of presetting, etc

Rationalization of all the aspects of the operation of adjustment

It is the third stage of the method. Its goal is to reduce the time of adjustment to the minimum.

Conversion into external adjustments made it possible to save time, but by rationalizing the adjustments, it is possible to reach the few minutes of réglage.
For example: use of split discs (attention, the hole must be larger than the nut).

External bonds

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