How often do you have to repeat a Gage R&R study?

Bev D

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#11
I do have R&R repeated when operators change for those sytems that are effected by operator technique/skill. These include visual inspection and NDE or destruct testing where sample prep and/or instrument operation are critical. For those systems that are heavily effected by operator technique annual or semi-annual R&Rs are conducted to maintain operator qualification similar to calibration studies on hardware.

I also have MSAs repeated when a part of the system is changed such as a holding fixture.
 
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Stijloor

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#12
Just for clarity and for the benefit of our Members:

Are we talking about MSA in general (which is comprised of various studies) OR Gage R&R specifically??
 

bobdoering

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#13
Re: Gauge R&R studies - How often do you have to repeat a gage R&R study?

Bob, I would think the time to perform a revised R & R is when the system has changed enough that the previous results are no longer valid. Most common, enough turnover in personnel that the user group has changed a lot. What are your thoughts?
If you performed the original test correctly, that is the participants represent the skill levels of those that you expect to use the gage, then it is still valid without periodic recertification. If the workforce skill set has diminished, such as you now use temps when before you had a steady workforce with established skills, then it will not be valid. But, gage R&R will be the least of your worries....

Still, that is still not a time function, as are the other MSA functions mentioned above. Think of it more as a special cause (like dropping the gage).
 

Bev D

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#14
good question. many people tend to use the phrase "Gage R&R" as a generic term to for all measurement systems analyses...

In my answer R&R is restricted to repeatability and reproducibility as appropriate for the situation. MSA is meant to encompass assessments such as method comparison as well as repeatability as appropriate.

For example I have a visual system that has substantial interaction with some inspectors at a certain range of results. Whenever a revision to the part of the system that effects the visual display is made we repeat our repeatability studies to ensure that all operators are repeatable across the range of results AND we perorm method comparison to ensure that the revised system is at least as effective as it was prior to the revision.
 
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bobdoering

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#15
Just for clarity and for the benefit of our Members:

Are we talking about MSA in general (which is comprised of various studies) OR Gage R&R specifically??
Good point. It always irritates me when people casually call gage R&R "MSA", when MSA the the full array of measurement analysis tools. By using the terms correctly, this confusion is avoided.
 

bobdoering

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#16
Re: Gauge R&R studies - How often do you have to repeat a gage R&R study?

Gauge R&R studies can be repeated based upon the frequency of the usage of instrument ,measurement criticality and equipment running cost
That may be true for calibration, but there is no justification to use this approach for gage R&R.
 

Bev D

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#17
Having burned my AIAG manuals in a Wiccan ceremony when I left the automotive industry, I now use the term MSA almost exclusively. I do this simply because I want people in my organization to recognize and utilize all of the appropriate analyses. We do have a detailed guidance document that describes each analysis and when each is appropriate or required to use.

Even when performing a Repeatability and Reproducibility, there are many study designs and analysis approaches beyond the 10 parts X 3 readings X 3 people with the incomprehensible table of statistical output accompanied by the mathematically invalid %tolerance thing. It isn't cookbook, the strudy designer must think about the situation and select the appropriate analyses.
 

Ninja

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#18
Re: Gauge R&R studies - How often do you have to repeat a gage R&R study?

Ever read through a thread as an outsider and see clearly that people are talking about two different topics? This seems to be the case here (though Bob and Bev are trying well to point this out too).

Gage R&R is a test to see if a measurement method (Gage and use of that gage) is appropriate for measuring a particular feature/characteristic.
It either is appropriate or is not appropriate...period.
Three years of waiting will not chage its appropriateness. Heavy use will not change its appropriateness.
A new customer will not change its appropriateness.
Based on this alone, Gage R&R is a one time proof.

When operators change, it may be worthwhile to verify that the new ones are using the same method. This does not require Gage R&R, though you may choose to use that tool.

When a gage is used heavily and may drift, it may be worthwhile to verify that the gage is still accurate and repeatable. This does not require Gage R&R, though you may choose to use that tool.

Bottom line is that Gage R&R does not have to be run again...the test method is appropriate for that which is being tested.
You may choose to run it again for some other purpose...but there is no need to check for appropriateness again.
 

Bev D

Heretical Statistician
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#19
Ninja - what exactly do you mean by "Gage R&R"?

AIAG uses a repeatability and reproducibility study design that they call Gage R&R. Many Customers require this Gage R&R to performed to qualify the appropriateness of the gage system. However, this is a very restrictive subset of the use of repeatability and reproducibility.

Simply because a term has a common or popular meaning doesn't mean that it is correct.
 
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