Changeover reduction is one of the pillars of lean manufacturing. The difference between setup and changeover time is that the latter is the time from the last piece of the previous batch to the first good piece in the next batch. It is this that should be minimised.

Reducing changeover time will enable us to produce in smaller, more frequent batches with the following advantages:

• Levelled production flow and output
• Improved flexibility (for the customer)
• Elimination of waste
• Reduced inventory
• Reduced leadtime

The late Shigeo Shingo has produced the classic work on "SMED" (Single Minute Exchange of Dies). SMED means being able to changeover within a single digit of minutes (ie less than 10 minutes).

Traditional thinking on Changeovers needs to be challenged in order to achieve reduced changeover times. Typical pre-conceptions include:

• Effective and efficient changeovers require lots of practice and experience.
• The effect of long set-up times is counter-acted by running larger batch sizes.
• The increased costs of stock-holding large batches is balanced out by running long runs to economic batch sizes.

By adopting the SMED methods defined, it is possible to make remarkable reductions in changeover time. An interesting analogy is the Grand Prix pit stop tyre change.