Gage R&R Study (Expanded)

Gage R&R - Variability

  

The Gage R&R output shows how the total variability is divided among the following sources:

·    Total Gage R&R, which can be broken into

-    Repeatability, which is the variability in measurements obtained when the same part is measured multiple times by the same operator.

-    Reproducibility, (which can be divided further into Operator, Operator*Part and other main and interaction effects), which is the variability in measurements obtained when the same part is measured by different operators at the various conditions defined by the factors in the model.

·    Part-To-Part, which is the variability in measurements across different parts. In addition to Part, there may be other factors used to calculate part-to-part variation.

Ideally, little of the variability should be due to repeatability and reproducibility. Instead, differences between parts (Part-to-Part) should account for most of the variability. This would be shown by:

·    A small %Contribution for the sources Repeatability and Reproducibility.

·    A large %Contribution for the source Part-to-Part.

The most important information is found in the %Contribution, %Study Var, %Tolerance, and %Process columns. These columns show the sources of variation. Typically, the Total Gage R&R should equal less than 30% of the study variation, and less than 10% would be ideal.

If you entered a process tolerance, an upper or lower specification limit, or a historical standard deviation, then either the %Tolerance or the %Process column may be more important than %Study Var.

Example Output

Variance Components

 

                            %Contribution

Source             VarComp   (of VarComp)

Total Gage R&R      7.0890          49.04

  Repeatability     6.8109          47.11

  Reproducibility   0.2781           1.92

    Operator        0.2109           1.46

    Station         0.0672           0.46

Part-To-Part        7.3672          50.96

  Part              7.3672          50.96

Total Variation    14.4563         100.00

 

 

Process tolerance = 10

 

 

Gage Evaluation

 

                                Study Var  %Study Var  %Tolerance

Source             StdDev (SD)   (6 × SD)       (%SV)  (SV/Toler)

Total Gage R&R         2.66252    15.9751       70.03      159.75

  Repeatability        2.60978    15.6587       68.64      156.59

  Reproducibility      0.52733     3.1640       13.87       31.64

    Operator           0.45921     2.7552       12.08       27.55

    Station            0.25925     1.5555        6.82       15.55

Part-To-Part           2.71427    16.2856       71.39      162.86

  Part                 2.71427    16.2856       71.39      162.86

Total Variation        3.80214    22.8128      100.00      228.13

Interpretation

For the refraction data, the Total Gage R&R %Contribution (49.04%) indicates that the measurement system accounts for as much variability as the Part-to-Part variability (50.96%). Furthermore, the Total Gage R&R equals 70.03% of the study variation. Repeatability specifically (68.64%) accounts for a large proportion indicating that the measurement system does not measure the same part consistently.