Gage R&R for every gauge? Or is it only every type of gauge? MSA 3rd Edition

G

ginn68

Per the MSA 3rd edition and QS-9000 is every gauge in the system required to have a GR&R on it?? Or is it only every type of gauge in the system needs a GR&R? I am confused on this matter!

Thanks for the help! :thanx:
 
D

D.Scott

MSA is done on "types" or "families" of gages. It isn't necessary to do an R&R on each of 50 digital calipers.

Dave
 

Jim Wynne

Leader
Admin
ginn68 said:
Per the MSA 3rd edition and QS-9000 is every gauge in the system required to have a GR&R on it?? Or is it only every type of gauge in the system needs a GR&R? I am confused on this matter!

Thanks for the help!

QS9000 4.11.4 says in part, Appropriate statistical studies shall be conducted to analyze the variation present in each typeof measuring and test equipment system. This requirement shall apply to measurement systems referenced in the control plan... (Emphasis added).

First, it is assumed that devices have been duly calibrated. If they have, there is no point in doing GR&R (for example) unless the study is specific to the part and feature in question. Having said that, and in recognition of the use of the word "type" in the standard, it is usually considered prudent and acceptable to qualify devices by type. If you have a feature for which you have sound statistical evidence that measurement with a (calibrated) 6-inch dial caliper is efficacious, it is not necessary to do GR&R for all calibrated 6-inch dial calipers on the same feature. Likewise, if the same device (or "system") has been shown to be efficacious in measuring a feature that is obviously analogous to one that has been previously qualified, it's not necessary to do MSA for that particular device, part and feature.
 
K

Kevin H

Several short comments - I agree that the GR & R should be done by family of gauges. At my last employer, we found different capabilities based upon manufacturer and decided that for given measurements you needed to group gauges by manufacturer and range. So for example, I could group Fowler digital electronic calipers, 0 - 6" range as a family. If I had also used Mitutoyo 0-6" digital electronic calipers, I would have had to do a separate GR & R for them, or if I had used Fowler 0-12" digital electronic calipers I would have had to do a separate GR & R for them. We also found that the human factor varied department to department making measurements in the same ranges, with similar but different brands of measuring devices, primarily calipers and micrometers.
 

Jim Wynne

Leader
Admin
Kevin H said:
Several short comments - I agree that the GR & R should be done by family of gauges. At my last employer, we found different capabilities based upon manufacturer and decided that for given measurements you needed to group gauges by manufacturer and range..

Part of the purpose of MSA was thus realized, but what happened next? If you found significant and statistically reliable differences between analagous devices from different manufacturers, one or both (of a set of two) had to have been wrong.

Kevin H said:
So for example, I could group Fowler digital electronic calipers, 0 - 6" range as a family. If I had also used Mitutoyo 0-6" digital electronic calipers, I would have had to do a separate GR & R for them, or if I had used Fowler 0-12" digital electronic calipers I would have had to do a separate GR & R for them.

I'm still puzzled; how often did you find a significant difference? I'm assuming that there were differences in repeatability, which is not all that unusual with digital devices, but did you find that one make was more repeatable than another in a linear and predicatable way?

Kevin H said:
We also found that the human factor varied department to department making measurements in the same ranges, with similar but different brands of measuring devices, primarily calipers and micrometers.

Now I'm really confused. Do you mean you had repeatability and reproducibility errors that you ascribed to differences in manufacturers? Operators were more likely to have problems with devices from certain manufacturers? If so, how did you manage to isolate the two types of errors?
 
K

Kevin H

Additional information re GR & R - I was managing a mechanical testing laboratory & our requirements for measurement acuracy were more rigorous than in other areas of the mill. Device repeatibility was in proportion to cost of the device - the "cheapy" digital micrometers were not as repeatable as the more expensive ones. Fowler was good, Starret was good, offbrands were not as good. (Both Starret & Fowler met our requirements in the lab for required total accuracy.) Actually, I should probably not have used calipers as an example - we didn't do the comparison on calipers we did it on micrometers & then extended the conclusions across the board.

The devices were used in different parts of the mill, for the similar purpose of measuring sheet thickness, but environmental conditions under which the test were performed were very different - I got stuck doing additional GR & R's because I was the lab, and because other departments had run similar studies and had shown more measurement issues. The question arose as to whether the instruments used had something to do with the different results from the different departments. I received 2 additional brands of micrometers (1 Starret & 1 off-brand) from other sections of the mill and used the same samples and operators with the new instruments to run the additional GR & R studies. The Starret gave similar repeatibility to the Fowler I used initially. The off-brand was not as repeatible. Operator reproducibility was similar for all 3 brands with the lab operators.

We used the average & range method, with 1 instrument, 10 samples & 3 appraisers - this permits breaking down the results into repeatibility and reproducibility. Under lab conditions reproducibility was better than under process conditions in the mill - we didn't delve deeper, but it wasn't surprising - considering environment, training, etc. differences between the 2 locations & sets of employees making the measurements.

Hope this clarifies matters somewhat.
 
G

ginn68

Thanks for the input!
I agree that every type of gauge should have a GR&R! If you go back to the standard (4.11.4) " This requirement shall apply to measurement systems referenced in the control plan" does this mean if an auditor comes and audits to the control plan, and wants to referance a gauge for the part # they are auditing it will be ok not have a GR&R for that certain gauge? But you do have a GR&R for another gauge of the same type?
 
L

lee01

With regards to the above:

What we have decided to instigate to control and understand our Measurement System is to conduct an initial GRR on Measurement Type (Laser Trackers, CMM & Various hand held devices) per product.

Then we measure a known artefact such as the SRS system from Metronom every week to create an understanding or trends etc.

We then re-do the GRR every year just to make sure people do not forget how to do it.

Calibration is based on errors found during the weekly artefact check.

With regards to our CMM, we have cut the cost by a huge amount simply by not calibrating it every year, but calibrating it as and when required from the NAMAS traceable SRS artefact.

We now understand calibration requirements clearly, understand GRR results etc.
 
R

Ramon Montoya

MSA For each Type?

My company just undergo the TS16949 certification, we passed the audit.

WE explain the auditor that we did the studies for each type mentioned on the control plan and to those that only measures a critical dimension of the assembly.

This was accepted, however MSA and his judgement will vary from person to person and auditor to auditor.

If your read the very first pages of the MSA manual you will see some comments that say that the studies referred on this manual should be implemented based on common sence... If I get the exact pages I will give it to you, this note allows it.

Regards...
 
Top Bottom