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Author Topic:   Gage R&R Study
David Drue Stauffer
Forum Contributor

Posts: 25
From:St. Louis, MO63132United States
Registered: Feb 2000

posted 09 February 2000 12:07 PM     Click Here to See the Profile for David Drue Stauffer   Click Here to Email David Drue Stauffer     Edit/Delete Message   Reply w/Quote
I recently embarked upon a journey to write a course (ppt pres.) to teach fledgling companies how to perform Gage R&R Studies.
In my endeavor to do so, I consulted the chat rooms of net. I pulled off a discussion that said,
"A typical Gage R&R study involves three operators taking two measurements of ten "identical" parts. The unlabeled parts should be passed to the operator in random order so that there is no bias when performing the measurements. It is important that the operator is not aware of which part they are measuring so that no attempt can be made to try to replicate the previous measurement.
After all of the measurements have been made, a series of calculations is performed to determine the % R&R. This value reflects how effective the measurement system is. A % R&R of less than 30% is considered to be acceptable by most industry standards."

When I learned to do R&R studies, I believe in accordance with AIAG, I understood that ten parts that were selected from a manufacturing process were to "labeled" 1-10, and a spot marked on each part as to the location the measurement was to take place in order to isolate gage system error from part process error!
It seems that if the parts were measured at random in random order from operator to operator, that this would introduce a sizable amount of variation into the equation that would make the grand average numbers quite high causing the resulting percentages to escalate! Also, 10% is the acceptable limit, not 30. 11-30 is acceptable ONLY based upon the application, in other words it has to be monitored closely. 31% and above would be unnacceptable under any conditions.
The above mentioned excerpt was from Ingersoll-Rand's Athens, PA plant that produces power tools.
If you have any comments or solution to either my or their understanding of how the R&R is to be conducted, please comment!
Dave S. davids@bcmac.com

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Dave S.

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Dawn
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Posts: 245
From:St. Marys, PA
Registered: Sep 98

posted 09 February 2000 10:24 PM     Click Here to See the Profile for Dawn   Click Here to Email Dawn     Edit/Delete Message   Reply w/Quote
I believe you both are correct, as the parts are to be checked at random, but also must be identified (marked). Mark the parts with a black marker in one spot on the part; number the back of the parts; then mix them up for each operator while someone else writes them down. They are still being checked at random, but they are also being checked in the exact spot. This will give you true readings.

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Laura M
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Posts: 299
From:Rochester, NY US
Registered: Aug 1999

posted 10 February 2000 09:07 AM     Click Here to See the Profile for Laura M   Click Here to Email Laura M     Edit/Delete Message   Reply w/Quote
I would add that the "measurement system" is being evaluated. If the parts can't be measured in the "exact same spot" when the gage is used in production, then you shouldn't specify where to measure for gage error. You may want to do that for diagnostic purposes...is it the gage or the process, but don't fool yourself. "Measurement System Analysis" isn't getting a gage to pass R&R.

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Marc Smith
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From:West Chester, OH, USA
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posted 10 February 2000 11:43 AM     Click Here to See the Profile for Marc Smith   Click Here to Email Marc Smith     Edit/Delete Message   Reply w/Quote
I've moved this to the Cal forum: https://elsmar.com/ubb/Forum4/HTML/000152.html

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