% Gauge R&R or Precision-to-Tolerance ratio

caroljackson — Thu, 28 Feb 2019 02:28:08 GMT

When reporting the Gauge R&R in version 13.1.0 the below report is available. When I open help, the below does not specify which is the % Gauge R&R number for the guidelines.

Example of the Gauge R&R Report

Note: To generate the reduced Gauge R&R report, select File > Preferences > Platforms > Variability Chart > Reduced Gauge RR Report.

In this example, the values in the Variation column are the square roots of sums of variance components scaled by the value of k (6 in this example).

Acceptable Percent Measurement Variation shows guidelines for measurement variation, as suggested by Barrentine (1991).

Acceptable Percent Measurement Variation

< 10%	excellent
11% to 20%	adequate
21% to 30%	marginally acceptable
> 30%	unacceptable

Note the following:

• If you have provided a Tolerance Interval in the Enter/Verify Gauge R&R Specifications window, a % of Tolerance column appears in the Gauge R&R report. This column is computed as 100*(Variation/Tolerance). Also, a Precision-to-Tolerance ratio appears at the bottom of the report. This ratio represents the proportion of the tolerance or capability interval that is lost due to gauge variability.

• If you have provided a Historical Sigma in the Enter/Verify Gauge R&R Specifications window, a % Process column appears in the Gauge R&R report. This column is defined as follows: 100*(Variation/(K*Historical Sigma)).

• The Number of Distinct Categories (NDC) is defined as (1.41*(PV/RR)), rounded down to the nearest integer.

Below are my results. If I use the 3.4% Gauge R&R then I believe my MSA is Excellant.

But if I look at the .81 Precision to Tolerance Ratio my MSA is not good as I would read this as 81%. Which is the correct number to use for the above guidelines?

Gauge R&R (copied as Text)

Measurement Source Variation (6*StdDev) % of Tolerance which is 6*sqrt of
Repeatability (EV) 0.0779517 77.95 Equipment Variation V(Within)
Reproducibility (AV) 0.0221650 22.17 Appraiser Variation V(Technician)
Technician 0.0221650 22.17 V(Technician)
Gauge R&R (RR) 0.0810417 81.04 Measurement Variation V(Within) + V(Technician)
Part Variation (PV) 2.3527216 2352.7 Part Variation V(Part SN)
Total Variation (TV) 2.3541170 2354.1 Total Variation V(Within) + V(Technician) + V(Part SN)

6 k
3.44255 % Gauge R&R = 100*(RR/TV)
0.03445 Precision to Part Variation = RR/PV
40 Number of Distinct Categories = 1.41(PV/RR)
0.1 Tolerance = USL-LSL
0.81042 Precision/Tolerance Ratio = RR/(USL-LSL)

Using last column 'Part SN' for Part.

Variance Components for Gauge R&R

Component Var Component % of Total
Gauge R&R 0.00018244 0.12
Repeatability 0.00016879 0.11
Reproducibility 0.00001365 0.0089
Part-to-Part 0.15375831 99.88 +++++++++

Re: % Gauge R&R or Precision-to-Tolerance ratio

Byron_JMP — Wed, 15 Jun 2022 13:49:31 GMT

Dear @caroljackson ,

I would like too introduce you to my friend Donald Wheeler. (I think of him as a friend, he likely has not idea who I am).

I could restate the problem as he puts it, or just post the paper here: https://www.spcpress.com/pdf/DJW189.pdf

The proportions, following the AIAG procedure, which JMP follows exactly, aren't really proportions. So it's possible to have both good, marginal and acceptable results simultaneously.

I highly recommend reading the paper in the link; however, you can't un-know the problem after you understand it, so read it at the peril of your bliss.

Best regards,

Byron

Re: % Gauge R&R or Precision-to-Tolerance ratio

statman — Wed, 15 Jun 2022 14:13:38 GMT

And to add to Byron's suggestion, get Wheeler and Lyday's book Evaluating the Measurement Process.

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% Gauge R&R or Precision-to-Tolerance ratio

Re: % Gauge R&R or Precision-to-Tolerance ratio

Re: % Gauge R&R or Precision-to-Tolerance ratio