If you want to calculate the capability of the gauge :
- first you have to do a bias study and calculate the bias B and the standard deviation of the bias σb
-after that comes the R&R study and the calculation of the R&R (see the Excel GRR Form)
-you calculate the uncertainty Um as follows (in Excel)
Um = abs(B) + sqrt((5.15*σb)²+(R&R)²)
-finally you calculate the Capability as follows
Cp = T / Um , where T is the tolerance range
Criteria :
Cp>=4 acceptable
Cp<4 unacceptable
NOTE.Uncertainty Um may be available from the calibration report , so no bias study would be necessary.
If there are no data of a bias study or calibration , some estimate a capability as follows :
Cp = T / R&R
Criteria :
Cp>10 acceptable
3.33<= Cp <=10 acceptable depending on the importance of the application , costs of improvements
Cp<3.33 unacceptable
Regards.