CTP--New Tools, Old Theories
One of the serious criticisms of the utilization rate is that you should not dedicate resources (staff) to operating a machine that is running 100 percent of the time, if that machine is not a bottleneck. The reason is that you are wasting some of your capacity (staff), which may be better used to address a bottleneck.
One of the main tenets of the Theory of Constraint is that you need to move the resources (staff) to the areas that are bottlenecks. And if that means leaving a piece of equipment idle, while resources are focused on the bottleneck, then that is better use of resources. Running a non-bottlenecked resource continuously to create a high utilization rate for that one piece of equipment can result in lower overall throughput.
There are two possible scenarios: The bottleneck could be before or the bottleneck could be after the resource with excess capacity. Often these theoretical discussions can become difficult to understand. Therefore, let's look at some case histories that may make this a bit easier to understand.
For example, let's take a printer whose platesetter requires a dedicated person, and the bottleneck is upstream, that is, before this resource (operator). In other words, the bottleneck is not in the platemaking area but in the digital proofing area. In this example, if the proof is made before the plates, then we have an example of a bottleneck (proofing) in front of the resource (operator) with excess capacity (platemaking).
A useful strategy to think about bottlenecks and how they move is to think about taking "snap shots" of how busy each department (another resource) is during different times of the day. In doing this, we would find minutes, hours or days in which there is work waiting to be done in one area—while someone else has nothing to do in another area. In this snap shot, the platemaking department has nothing to do, while the proofing area has too much work.