SMED - How Did It Come About?

SMED or Single Minute Exchange of Dies was developed in around the late 1950's early 1960's by Shigeo Shingo. Shigeo was working as a consultant for various companies at the time including Toyota at this time. Toyota Recognised that the EBQ (Economic Batch Quantity) of their products was too high, this was due to long changeover times.

Toyota realised that the most difficult and time consuming task involved in a changeover was the changing of the dies on transfer stamping machines used to mould car bodies. These dies are different for each model and very heavy (weighing many tonnes) and must be assembled to a tolerance of a couple of mm's to assure the quality of the panel.

The current process was to stop the production line, let down the die by crane, position the new die by eye and then to run test pieces adjusting after each failed piece by crowbar. This took anything from 12 hours to 3 days to complete.

Toyota then took the following steps to reduce this time..

1. Placed precision measuring equipment to measure the setting distance of the dies rather than doing this by eye, and recording the measure for each body so that it could be obtained first time every time.
2. Made it so that the dies were always changed in the same sequence every time.
3. Dedicating tools to the operation so that the required tools were available and nearby every time a changeover occurred.
4. Scheduling the use of the overhead crane so that the new die was nearby and ready to be assembled as soon as the old one was removed.

Using this system Toyota were able to reduce the changeover time from the old time to 10 minutes. This gave them an EBQ of less than one car per run.

Shigeo claimed that the average setup he dealt with was reduced to 2.5% its original duration, this is a 40 times improvement.

SMED describes two types of activity during a changeover. Internal activities are unable to be carried out with production or the line carried out. whereas external can be carried out along side production or the line.

Shigeo Shingo recognises eight techniques that should be considered in implementing SMED.

1. Separate internal from external setup operations
2. Convert internal to external setup
3. Standardise function, not shape
4. Use functional clamps or eliminate fasteners altogether
5. Use intermediate jigs
6. Adopt parallel operations
7. Eliminate adjustments
8. Mechanization

How dividing Internal and External activities and then reducing the duration of these activities reduces setup time 

SMED is now classed as one of the most benificial areas of improvement in production, and is a vital part of running a lean organisation. With many case studies on the internet of successful SMED the reasons that companies use SMED are obvious.

Formula 1 Pit crews use SMED to carry out the
 changing of  4 tires in under 3 seconds, whereas it
 would take one person around 15 minutes or more.