GAUGE R&R STUDY

  

Measurement System Analysis

Chapter 10

Gauge Repeatability and Reproducibility ( GRR )

* GRR is Gauge Repeatability and Reproducibility.

 
* GRR, Repeatability and Reproducibility follows Pythogoras theorem.

* Equipment Variation ( EV ) :

                                                  Equipment variation is Repeatability.

* Appraiser Variation ( AV ) : 

                                                 Appraiser variation is Reproducibility.

* Part to Part Variation ( PV ) : 

                                                  Variation from part to part in the process.

* Total Variation ( TV ) :

                                            Cumulative variation due to PV and GRR.

* % EV = 100 ( EV/TV )

* % AV = 100 ( AV/TV )

* % GRR = 100 ( GRR/TV )

* % PV = 100 ( PV/TV )

* NUMBER OF DISTINCT CATEGORIES ( NDC )

NDC = 1.41( PV/GRR)

When SPC not used , ndc >=2

When SPC is used , ndc >= 5

* ACCEPTANCE CRITERIA

1) If % GRR < 10 %

          Gage system is acceptable.

2) If 10 % < % GRR < 30 %

          Gage system may be acceptable ( Based on importance of application , cost of gage , cost of repair etc. )

3) If % GRR > 30 %

          Gage system needs improvement.

Elements of Total Variation in Observed Data :