Q: We are slitting coils into steel bands. How should the time needed to change coils be integrated into the cycle time of the slitting machine?
Situation: A large coil of steel-foil is placed in the slitting machine. The steel-foil is un-winded and slitted in several steel bands. At the end of the coil a new coil must be placed in the machine and the process goes on.
Arno Koch • The goal of OEE is to visualize ALL losses. When the machine is not slitting although there would be a demand, this is a loss. Even if (you think) you cannot avoid it. This loss can be visualized in two manners:
- As waiting-time in the availability or
- as a performance loss (it would be considered to be a minor stop).
Make losses visible!
When the changeover time would be settled in a (reduced) cycle time, the loss would not become visible, and probably changeover time reduction will hardly become a subject of improvement activities.
As a rule of thumb, usually a waiting time larger than 1 to 5 minutes is to be considered as an availability loss. Since a coil-change normally takes longer than a minute, I would suggest to register this as ‘coil changeover time’ and visualize it in the category ‘waiting time‘. (Meaning: The machine is waiting until the coil is being changed). In that way it is possible to see how many times we change a coil and how many minutes of potential production time is being lost. By applying SMED or eventually modifying the equipment, this loss might be minimized.
Cycle time slitting machine – Conclusion:
The cycle time of the slitting machine should be base on slitting and slitting alone. This is it’s sole purpose!