What is it?
Evolutionary operation (EVOP) was introduced in the 1950s by George Box and it is a methodology for process improvement based on the principle that processes generate products or services together with data useful for providing guidance for improvement. It use an operating full-scale process, therefore the information how to improve the process is generated from a simple experimental design while production is underway. To avoid unwanted changes in the product's characteristics, only small changes are made in the levels of the process variables. EVOP is designed for work of process operators on a full-scale manufacturing process while it continues to produce satisfactory products.
Why is it important?
Classic experimental design are methodologies which help us to set up an optimum combination of the design factors and their proper levels for the manufacturing process. They are very powerful tools; but they cost money, time, manpower and require special training to conduct the experiments. Very often they interrupt production. On the other side EVOP is a tool in which a continuous investigative routine becomes the basic mode of operation for the plant and replaces normal static operation. EVOP is a useful tool in the manufacturing and service process environment because it generates ideas for process improvement, helps establish cause-and-effect relationships, and if done properly, it all comes for free.
When to use it?
The basic idea is to replace the static operation of a process by a continuous and systematic scheme of slight deviations in the control variables. The effect of these deviations is evaluated and the process is moved in improvement's way.
How to use it?
There are one/two/three factor EVOP designs.
Single Factor EVOP Design:
- If X were to be current production level, usually it is aligned as the new center of specification and is identified for designed experiment.
- Decide which are acceptable levels, X-D and X+D (within the specification limits), when the OK products are still produced.
- Evaluate the quality of process in each level (X, X-D, X+D) and identify which level produces the products with the highest quality.
Two Factor EVOP Design:
- You have current production level and two factors (X is first, Y is second). If these are identified, evaluate the quality of the output at all different combinations of X and Y, do not forget to include D to set the conditions right. Your new center point is that combination of factors and D which produces the products with the highest quality.
- Repeat EVOP for the next cycle of continuous improvement.
Then there is the three-factor EVOP which goes on same lines as above but with three factors.
Author: Jana Loskotova