AAOM Handbook

A Stable Process will produce some variation in its outputs, however these variations will be distributed in a random pattern. The average of the output values, and the range of deviation of individual output values from the average, will be consistent. The benefit of having a Stable Process is that it is not changing, therefore its future performance should be the same as its past performance – ie performance in a Stable Process is predictable. Producing a stable Process requires that the all elements of the Process occur in the same sequence, and in the same way, each and every cycle. Machines, robots and computers are very good at doing exactly the same thing over and over, whereas people are very poor at this. This is the underlying reason that process automation and computer controlled robots and machines have yielded such enormous productivity and quality improvements in industry. However, since many elements of our work processes must continue to be performed by people, a fundamental challenge in achieving stable Process performance is to establish appropriately standardised completion of the work people perform. The Business Process Framework (BPF) is a system designed to help achieve this. Excessive variation in output is waste produced by the Process. If you increase the output of a wasteful Process you will also increase the waste produced. Therefore the logical steps to improving the capability of a stable Process are firstly to reduce the variation to less than the specification limits, and then to look for a change that will move the output to the desired target. A good analogy from target shooting is; if your shooting is producing a very wide pattern of hits, trying to adjust the sights will not produce any improvement. You have to focus on achieving a tight pattern first, by improving the consistency of the position/aim/fire process. When you have a tight pattern that is consistently displaced from the target you can get on target by adjusting the sights. A Capable Process is one that is Stable and delivers the customer’s expectations (ie it meets the specifications).