In part one I explained SMED is a systematic approach to quick changeovers in order to minimize machine downtime.
In order to explain what SMED is good for to non-specialists, I used the laundry example, in which the mundane washing machine is a very precious resource and it should wash (add value) as much as possible in 24 hours a day. Conversely, such a precious resource should be protected from any downtime, especially when changing (laundry) batch.
After describing a typical lengthy and far from efficient changeover, this second episode will show how to drastically improve the performance by reducing the changeover duration.
Distinguish internal and external setup
The very first thing to understand when striving to reduce changeover duration is to distinguish internal and external setup operations.
Internal Setup (IS) operations are done within the machine or so close to it that safety requires to have it stopped to achieve them. Typically changing a tool fixed on a machine or adjustment inside the machine.
External Setup (ES) operations either have nothing to do with the machine itself, like filling a tracking record form or bringing raw material from warehouse near to the machine, either can be achieved without endangering oneself. ES operation can be achieved while the machine keeps running.
Many times, some operations and task are first seen as External Setups, but after closer analysis are totally unnecessary. This happens often when countermeasures to some old problem have not been suppressed after the problem was settled.
Internal and external setup with laundry
Back to our laundry problem; what are internal and external setups?
Considering the chart of a typical changeover as displayed hereunder,
“Searching for empty clean basket” to receive the washed laundry and “searching for detergent” and “sorting laundry” should not happen at the expense of machine time. These operations should be included in preparation prior to changeover, which is External Setup.
If work environment, here laundry room, is well organized and tidy, searching for items like basket and detergent should be unnecessary. Even so in preparation – External Setup – this time is not impeding the washing machine performance, it can be saved for more valuable occupation.
The changeover duration after separating ES and IS should be drastically reduced to almost bare minimum. Almost, because the remaining IS operation are likely to be optimized (reduced).
The changeover process after improvement should look like this:
This simplified laundry example is very similar to the changeover duration optimization done in production lines, machining cells, etc.
When working to reduce the machine downtime during changeovers, most of people try to improve some technical aspect like fittings, fastenings, jigs and so on. As this fictional example shows, most of the improvement potential is found in organization.