Appraiser Out of Control

Hello,
I'm fairly new to this Gage R&R and we used a sheet that we found online. However, the sheet is telling me that we have an appraiser "Out of Control" when they are making very accurate and precise measurements. Based on the math, it looks like if each appraiser had a wider range (instead of being exact or having a smaller range of 3 separate measurements), then there would be no appraisers out of control. I can't wrap my head around the concept that if all the appraisers had less precise measurements, then the appraiser would NOT be out of control. Is this true? Thanks,
Terry

Terry.

That's the R&R we use!

It's saying Appraiser C is out of control because everyone else and every other measurement has no variance. So since Appraiser C has found slight variance in one measurement they need to be beaten over the head with a blunt object, sent back to metrology school and be judged on their incompetence. Perhaps a written warning is needed. First in line for downsizing when business slows down. It's quite logical really and very handy when the formulas do the thinking for you.

On a serious note, that is why they are judged "out of control". A fix would be to get a sample of parts which reflect the total expected variation (start up, mid run, shut off, tool wear, etc etc) but perhaps even that would not be enough depending on your process and run the R&R again. Another would be that your measurement tool is not sensitive enough and in the eyes of the R&R and perhaps your customer it is unacceptable; so budget and common sense permitting you could retry the R&R using a CMM. But, looking at your data and assuming this is the expected variation of the process and assuming you are using the measurement tool not for SPC purposes, why would you? Getting more resolution would not be of interest to you, the observed variation is tiny and all appraisers are in agreement that part 7 is a little smaller than the rest.

I'm not a fan of R&R's as they either suggest that the appraisers or the measurement system needs a blunt object combined with gravity but I must due to automotive requirements. I tend to do an R&R and plug that data into Wheelers Honest Gauge Study and use that to supplement thinking and decision making. This thread may be of interest to you.

Best of luck.

Hi,

Your study has 10 parts, 3 Operators with each part measured 3 times, this makes 90 measurements which are organised in sets of 3 repeated measurements per operator per part. The R (Range) referred to in rows 5, 10 and 15 indicates how well the measurement process repeats for the constituent part against the operator.

All your Ranges are 0 except for part 7 where Operator C has an apparent observation which differs from not only theirs but everyone else. The reason that the sheet flags up that appraiser is that it thinks that there is effectively no variation in the process therefore its set an upper range control limit to 0.

What you have to ask yourself is whether you believe that a 0-150 mm calliper (presumably digital) can repeat at that level for over 89 observations over 3 operators. The resolution of such instruments is usually around 0.010 mm so anything from 0 - 0.010 mm is in the noise.

The variation shown for part 7 and operator 3 is consistent with the resolution. Based on my experience using these instruments, measuring standard features and a 10 x 3 x 3 study I would expect the UCLR in row 19 to be around 0.026 mm ( 0.01 x D4 (2.574) thus comfortably enveloping a working resolution of around 0.01 or even 0.02 mm for this instrument.

Hope this helps

Did you ensure that the appraisers doesn't have access to their previous readings while doing this study?

Johnny, Welshwizard, thanks for your replies. Makes me feel better that the result is... the result.
Amit - No, I did not. The measurements were performed by our supplier.

Sorry @umctkim , but the measurements seems doubtful to me. Only one reading in total 90 readings is showing variation, which I didn't come across in any practical MSA study.
Better do the MSA study with the supplier physically.

Hey guys, is it possible for someone to send a link or the attachment for the GR&R form OP used? Thank you!

umctkim said:

Hello,
I'm fairly new to this Gage R&R and we used a sheet that we found online. However, the sheet is telling me that we have an appraiser "Out of Control" when they are making very accurate and precise measurements. Based on the math, it looks like if each appraiser had a wider range (instead of being exact or having a smaller range of 3 separate measurements), then there would be no appraisers out of control. I can't wrap my head around the concept that if all the appraisers had less precise measurements, then the appraiser would NOT be out of control. Is this true? Thanks,
Terry
View attachment 27869

Click to expand...

In my humble opinion this study looks like a manipulated Gauge R&R. Think about it that way - is the process of your supplier so capable and accurate that the output of it is capable of producing 78 parts exactly 25.370? This study almost eliminates factors such as part-to-part variation, operator-to-part variation or operator-to-operator variation or within gauge variation.

sbailey020 said:

Hey guys, is it possible for someone to send a link or the attachment for the GR&R form OP used? Thank you!

Click to expand...

@Johnny Quality Can you help with this request?

Sorry but I no longer work where we used that template.

It was a free template I found online, I'll do some digging in the hope I find it