Gage R&R (Repeatability and Reproducibility) for Dummies

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D

Don_Amaru_Sarma

#42
By the way I have a question. Why is the standard set at 10-30% Not a more stringent measure such as 5%. Because in the plastics industry usually we practice an error level of <5%.
 

bobdoering

Stop X-bar/R Madness!!
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#43
By the way I have a question. Why is the standard set at 10-30% Not a more stringent measure such as 5%. Because in the plastics industry usually we practice an error level of <5%.
Clearly the smaller the better. For some applications the investment in gaging to reach a lower gage error level is not justified. BUT...10-30% is abjectly inadequate for SPC use. In fact the error should be less than 10% of the control limit range, NOT the specification! Otherwise, your true process distribution will be masked by gage and measurement error (although you won't know it and be tickled to see a normal distribution - typical of measurement error!)
 
A

AmQC01

#44
Extremely confused when is comes to tolerance range/ total variation. For one are they the same? Is the total variation something that my form should be filling in. I was told that this should be the total difference between the tolerence. Is this true? Please help.
 
A

Avelar

#46
Hello all,

I got some questions, I would appreciate if you can help me. What is the difference between the total variation and the tolerence in the form to obtain the R&R? Other question, when I made the study for one gage, the variaton between operaters was 0,01 at maximum and the values were all within specification, why I got 22% of RR?

Many Thanks for your support
 

Jim Wynne

Staff member
Admin
#47
Welcome to the Cove :bigwave:
I got some questions, I would appreciate if you can help me. What is the difference between the total variation and the tolerence in the form to obtain the R&R?
GR&R results may be expressed as percentage of:
  • Total variation--the actual process variation, if it's known;
  • Within-study variation--as its name suggests, only the variation seen in the GR&R measurements is used;
  • Tolerance--the amount of the total tolerance being consumed by measurement error.
Generally speaking, the first two are used when a measurement system is used for process control--doing SPC, for example--and the third is used when the system is used for inspection.

Other question, when I made the study for one gage, the variaton between operaters was 0,01 at maximum and the values were all within specification, why I got 22% of RR?
The question can't be answered definitively without seeing the data, but one cause might be that the 0.01 variation comprises a significant amount of the tolerance, or that part variation (within and/or between parts) was high. If you could post the actual data we can give a better answer.
 
A

Avelar

#48
Hello Jim,

Many thanks for your support. I am new in this forum, I will try to introduce an exemple with the values, specification and the R&R result.
 

Jim Wynne

Staff member
Admin
#49
Hello Jim,

Many thanks for your support. I am new in this forum, I will try to introduce an exemple with the values, specification and the R&R result.
You're welcome. Our own MSA guru Miner has posted comprehensive MSA information in a series of blog posts here at the Cove. It's a treatment of the subject you're not likely to find anywhere else.
 
A

Avelar

#50
Good Morning,

Attached you can find an example of a RR study that I have performed. The specification is 11.2 and the tolerance is +0.2 to -0.45.
The study has 2 operatores, 3 trials. The difference between operators is very small but the result is too high. If it is possible can you explain this situation?

I thank you in advance.
 

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