My EVOP story
My first co-op job way back in the early 80’s was at a mine. I had an entry level job tending an on stream process analyzer. I had no idea what the thing did, so after a few weeks I followed the wires up to a control room.
The guys there said the whole mineral processing plant was run by computer. Teletypes and PDP-11s! My device sent information on the content of Lead and Zinc, and then the computer did EVOP to improve the yield.
They gave me the best description ever of how EVOP works.
If you were blindfolded and placed on the side of a hill, how could you most quickly get to the top? What you would do is plant you left foot (the origin) and step with right foot four times at 90 degrees. One direction would be up (increased yield). Now move your left foot to the new highest point and test with your right foot again. You only need to do this 3 times since you came from the low point. Continue on until you get to the top of the hill.
You are mapping out the hill topology or response surface.
The fun becomes when you apply it to more than one variable. It still works, but can no longer be easily described in words.
They had data that showed that starting Friday night and ending Monday morning the EVOP computer system continually improved things. When the process engineers got to work Monday morning “improving things” yields got worse.
Being a dumb student at the time I only now realize what an incredible thing they had set up.
I saw EVOP again 15 years later at a die cast shop. They ran 0% scrap, had tapped out SPC, (Cpks > 20 on key process parameters) and now had the operators running EVOP to decrease cycle times.
A very cool tool, one I hope to use some day.