CTP--New Tools, Old Theories
For example, you discover that your platesetter is running 90 percent of the time during one shift. In other words, approximately eight out of 24 hours, resulting in a low, 30-percent utilization rate. Further research shows that your on-time delivery is 50 percent, because the presses on the second shift are running out of plates. Although you could conclude that you need another platesetter, a less expensive option would be to start a third shift.
On the other hand, if you find that the platesetter is being utilized 75 percent of the time across three shifts, and your press utilization rate is only 60 percent because they are waiting for plates, then it may mean it's time to buy another platesetter.
In summary, utilization rates are a traditional measurement that can be used to help assist in purchasing decisions. The utilization measurement is most useful when the resource measured is the bottleneck in a workflow.
However, a low utilization rate in a non-bottlenecked area requires further investigation. The resource may add value to the perception of your company, or it may be scheduled in a way to synchronize manufacturing. Either way, it does not mean that the resource (equipment) is not performing well or should be outsourced.
The drum-rope-barrel theory of scheduling is part of the Theory of Constraint philosophies discussed in the book "The Goal." In essence, the theory says it is better to turn off a resource for a period of time when its capacity exceeds demand.
Turning off the resource will result in a poor utilization rate. However, if this is not a bottleneck, it should not be interpreted to mean that the equipment should be sold or that the company should not consider replacing it. A low utilization rate, due to the drum-rope-barrel theory of scheduling, in a non-bottlenecked area could result in greater overall throughput.