Gage R&R with only one operator using JMP
Gage R&R with only one operator using JMP
(OP)
For example, I measure the width 3 gage blocks, 1.000", 2.000", and 3.000". I measure them 10 times each and repeat it once as the same operator. I would like to know the amount of the tolerance that is being taken up in my measurement? I would calculate the P/T ratio. Do I have to repeat my measurement twice, or since I am the only operator can I do it only once? The JMP manual does not help in this regard. If you could point me to a good book for reference on Gage R&R's that would be great as well I could not find any.
Thanks.





RE: Gage R&R with only one operator using JMP
As far as references on GR&R, you should be able to search the net. There are LOTS of good references out there.
RE: Gage R&R with only one operator using JMP
I am aware of the 3-10-3 idea. Our application involves a CMM machine that is automatically doing the measurement. Only one operator will be running the machine. Could JMP calculate the Repeatability section using only 1 operator? I know this has been encountered in industry before.
RE: Gage R&R with only one operator using JMP
RE: Gage R&R with only one operator using JMP
Also, when performing your repeat measurements, it is CRITICAL that you redo your setup. That is to say, you MUST tear down your fixturing and set it all back up. (Moving your fixture to another location on the actual CMM would be another operator....). Ideally, you would tear down your setup in between every measurement, but his often proves too time consuming. Therefore, I have always torn down my setup in between trials, i.e.
1) Measure units 1-10 in ascending order
2) Tear down and build up my fixture (if using fixturing blocks)
3) Calibrate the CMM to my fixture
4) Measure units 1-10 in descending order
5) Repeat 2 & 3
6) Measure units 1-10 in random order.
With a CMM, there usually isn't a dependency on measurement order, but it is a fairly trivial step to remove all doubt.
Hope this helps!
RE: Gage R&R with only one operator using JMP
Also, have you heard of a gage verification study? I was reading a new paperbook titled, "all about six sigma" about the authors opinion about how a gage verification study may be a good option versus a gage R&R. The biggest difference is you use a known standard part instead of actual production parts, and you find the total variation by 3 people each measuring the known standard 7 times. You find the average and standard deviation of all 21 measurements, and to find the P/T ratio, all you do is:
P/T = ((5.15*StDev)+ ABS(Known Standard - AVG)) / (USL-LSL)
The author of this book feels that anything from 10 to 30 percent is good, and anything >30 percent needs to be improved. It seems much simplier in some cases. What is you opinion on that. The 5.15 refers to 99% of the variation of a normal distribution. A known standard could be a gage block or a sample part that a lab with greater measurement equipment has agreed upon. I am very interested in this area. Any feedback would be appreciated.