SMED
Quick changeovers
for less downtimes

SMED Single Minute Exchange of Die

Once well aware about the causes of the waste of time, the Toyota engineers worked to eliminate waste and built the SMED quick changeover method.

Single Minute Exchange of Die = Exchange dies in less than 10 minutes.

Single Minute Means: setup time is reduced to be counted on a single digit.

Four steps to SMED

The first obvious thing noticed by the engineers was that during changeovers and setup the machine was stopped, even for operations that were totaly independent of the machine itself, like preparing tools, dies or various supplies. This led to a first step of the SMED approach:

Discriminate operations that MUST be done while machine is stopped, called internal setup (IS), from those possibly done while machine runs, called external setup (ES), and useless operations.

By hunting down all causes of time waste, the SMED team finally came up with a sequence of four steps to reduce changeovers:

1. Suppress useless operations, convert IS operations into ES
2. Simplify fittings and tightenings
3. Work together!
4. Suppress adjustments and trials

External setup tasks

The first quick wins are brought by reconing external setup tasks and treat them like that: do them before the changeover, before stopping the machine. External setups are typically preparations of prerequisites:

• tools, parts
• instructions
• lifting material
• pre-assemblies

Besides, take opportunity to unify parts storage, boxes, crates, feeders size and types.

Internal setup tasks reduction

Some operations seen at first glance as "internal" can be converted into "external" with significant reduction of machine stoppage. These operations can be: presets and pre heating (in external owen, with external connection...)

Once conversions done, simplify fittings and tightenings

When all operations that can be done without stopping the machine have been identified and converted, the next potential for setup time reduction lays in the reduction of the "internal" operations. Among them, fittings and tightenings are a major category. The target is to:

• suppress fittings and tightenings partially or even totally
• minimize " turning " movements: they request several grasp-release motions!
• fit at once, in a single motion
• use blocks, jigs, templates
• standardize tools, types and size of screws, nuts...

Adjustments

Once the die, fixture or template for the new batch is set, it is usual to have several adjustments to do.
These adjustments are also time consuming and extending the duration of machine stoppage. Adjustments can be considered as waste. Would the setting be done properly the adjustments wouldn't be necessary.

• fix standard values
• find out adjustment-less methods through physical means, like stoppers, guides, blocks...
• design custom made tools if necessary

Work together!

If a critical machine stop is to be reduced to the very minimum, it is meaningful to have a team caring about. This team is made of the operators and techies from the workcell or workshop that temporarly let their current task down to help to perform a quick changeover on the critical machine. This setup would act like the racing pit team, each team mate being assigned a special operation he knows well and performs flawlessly in a very short time.

Trials

Trials are like adjustments, to be considered as waste as all should be organized and done to make it good at once, without any need for trials.

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