SMED is a systematic approach to quick changeovers in order to minimize machine downtime.
To explain what SMED is good for to non-specialists discovering it, I use the laundry example.
Let’s imagine the mundane washing machine is a very precious resource and it should wash (add value) as much as possible in 24 hours a day.
The machine stops at the end of a washing cycle and there’s no choice but swapping washed laundry with a new batch to-be-washed laundry. This exchange is equivalent to production changeover. In order to minimize the washing machine stoppage, the laundry swap has to be as swift as possible.
But before designing a laundry cannon to shoot the clothes high velocity into machine’s drum, let us observe how a laundry swap is done (go see).
The usual changeover cycle
When the machine stops at the end of a cycle, the “operator” has to notice it and be ready for action. If the machine does not signal itself and/or the operator is not waiting for this moment, the reaction time until noticing and acting is wasted.
The first thing to do is to remove the washed laundry from the drum. This clean laundry should be protected against stains and put in a clean empty basket for example.
Ah! Empty basket? Where is the empty basket? The time searching for the empty basket with arms full of clean laundry is lost for washing as the machine sits idle waiting to be fed another batch.
When the clean laundry is eventually dropped into a clean empty basket, and assuming the “operator” does not waste additional washing machine time to further take care of clean laundry, he’ll has to come back to the machine to load it with the next batch of laundry to be washed.
At this point boys have to understand to their amazement that delicate, white, dark and light laundry have to be sorted and washed separately, except for those who like their white shirt turn light pink thanks their daughter/sister/wife’s blouse. Girls usually know this.
If the to-be-washed laundry was not sorted beforehand, the time to sort it lets the machine idle and wasting more time.
Finally, one part of the sorted laundry is thrown into the drum, a gesture that could have be done in a softer manner, as the violent acceleration of clothes does not compensate much of the time lost until that point.
The changeover is not finished as long as the machine is not restarted. And before restarting, it should be refilled with detergent.
Detergent? Where’s the detergent?
While searching for detergent, the machine… sits idle.
When detergent is filled and machine started, the changeover is done.
Instead of washing machine we’ll find machine tools or any production or test equipment. Instead of laundry it’s raw material or parts and instead of detergent, operators may look for tools, templates, jigs, plans or whatever should be handy and is not.
In the next post of this series, we’ll see how the washing machine downtime can be drastically reduced!