# Gage R&R and Capability - Between 10% and 30% and cannot be improved

M

Question:

I have once read (I think) that if the gage R&R is between 10% and 30% and cannot be improved, a correction of the capability indices has to be done. Does anyone know the formula to how the Cp, k and Cpk are corrected?

Thanks.

#### Marc

##### Hunkered Down for the Duration
Staff member
Any ideas, folks? I'm lost with this one.

M

For those interested, I found it (with no small effort I might add).

It is in the word file attached since I couldn't paste the image directly. It is only applicable to the Cp since % R&R is not dependent on the target.

I am intoducing into our Cp, Cpk, k policy that if a measuring equipment has a gage R&R between 10% and 30%, the equipment can be used but the Cp has to be corrected until the measuring equipment can be corrected.

Cpo is the measured Cp where Cp is the process capability once the measurement equipment uncertanty is removed. You will notice that for % R&R values of less than 10%, Cpp and Cpo are practically the same. It is for values of 20 to 30% that the formula is usefull.

Hope it helps.

#### Attachments

• 14.5 KB Views: 372

#### Marc

##### Hunkered Down for the Duration
Staff member
Thanks, Michel! The contribution is appreciated. I'm sorry no one here knew the answer. :thedeal:

#### Atul Khandekar

##### Quite Involved in Discussions
R&R to Cpk

This one I had downloaded from pdf zone or from dWizard's (I dont remember correctly). Its a small article on relationship between R&R and Proces Capability.

Hope this helps.

- Atul.

#### Attachments

• 17 KB Views: 410
Capability or Gage R&R Study for Leak Tester? Reliability Analysis - Predictions, Testing and Standards 15
Capability or Gage R&R Study for Leak Tester Reliability Analysis - Predictions, Testing and Standards 11
V Supplier Capability and 100% Sort causing Gage Wear APQP and PPAP 1
D AIAG 4th Edition Capability Study and Gage R&R Requirements Document Control Systems, Procedures, Forms and Templates 8
E Capability of Gage (Cg & Cgk) for New and Repaired Gages Capability, Accuracy and Stability - Processes, Machines, etc. 10
B MSA (Gage R&R) vs. Capability Cpk Study - Helium Leak Check Station Statistical Analysis Tools, Techniques and SPC 2
T Machine GR&R (Gage R&R) - Capability Study Capability, Accuracy and Stability - Processes, Machines, etc. 5
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Operator Capability - Gage R&R Poor Repeatability Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 8
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