OEE improvement strategy using a machine monitoring system
Your OEE improvement strategy needs a method of tracking downtime, rejections and cycle times 24/7. OEE, or Overall Equipment Effectiveness, is a brilliant invention that, in a single number, tells you how much waste there is on your shop floor. It is merely the ratio of what you produced to what you could have produced – the actual output to the theoretical maximum capacity. It is a direct measure of your profitability and return on investment. OEE improvement directly translates to profitability improvement.
Availability: Is the machine operating or not? The ratio of the time that the machine was running, to the time that it could have actually run. The difference is because of idle time caused by breakdowns, setup, shift-change, etc.
Performance: How fast is the machine running? The ratio of the number of parts produced to the number of parts that theoretically could have been produced in the time that the machine was running. The difference could be because of inspection, insert changes, tool breakage, etc. between the start and end of a cycle. On a CNC machine, the difference could be due to using the feed rate or spindle speed override.
Quality: How many good parts were made? The ratio of the number of parts that pass quality inspection to the total number of parts made. The difference is the number of parts rejected. OEE allows you to measure and reduce waste (of available time, machine capacity, raw material) on the shop floor. It is a single number that you can communicate to, and is understood by, everybody from the machine operator to the President. It can be tracked month-on-month, improved upon.
Available time in a day = 20 hours (minus meal breaks and shift changes).
Running time = 16 hours (4 hours lost due to breakdowns, setup change).
Theoretical production=200 parts
parts Good production=160 parts Availability= 16/20 = 0.8
Performance= 180/200 = 0.9
Quality=160/180=0.88 OEE = A x P x Q = 0.8 x 0.9 x 0.88 = 0.63
Notice how fast we go from “Ah, those are great numbers for A, P and Q” to “Oh man, this OEE kind of sucks” ? This number means that only 63 % of the available capacity is being used, and there’s a 37 % wastage. That’s awful, but it’s way better than the number in an average shop floor. In terms of return on investment, 63 % OEE is like paying for a banana, and getting only 2/3 of it.
You cannot improve your OEE unless you continuously measure and track it and its components A, P and Q. Your OEE improvement strategy must include a machine monitoring system that automatically tracks production, machine downtime and rejections.
‘Mix’ on the Deccan Queen
On the Deccan Queen (lovely name for a train, isn’t it ?) from Pune to Mumbai recently, I had a new food experience. The train has a nice dining car, something that I haven’t come across in any train in India. There’s also an attached kitchen where everything is cooked fresh, instead of cold food being loaded from a wayside station.
Mix (sorry, the pic. was taken when the train shook rather violently – note the ripples on the surface) After a breakfast of Sabudana vada, I heard someone ordering something called ‘Mix’, was intrigued and asked the waiter what it was. It turned out to be a mix of coffee and tea, and since I have a mental problem that makes me any order any food that is new and unusual, I ordered the Mix instead of one of the two beverages separately. I was given a cup of coffee with a tea bag sitting in it, and the taste was (obviously) a hybrid. I thought it was interesting but not great, although my fellow travellers in the dining car seemed to be quite addicted to it.
An occupational hazard of being a ‘eat anything that looks new and interesting’ guy is that I sometimes end up with truly ghastly tasting stuff. This experience thankfully wasn’t one of those.