Interpretation of the Graphs:
Step 1: Measurement Stability
A stable measurement system shows no out of control points or "non-random" patterns or trends in the range chart
Step 2: Resolution/Discrimination
Adequate resolution or discrimination means that the measurement units (inches, tenths of inches, thousandths of inches,…) are sufficiently small enough to be able to "see" variation.
- Stratification on a range chart is a good indication that there is a problem with inadequate resolution.
- The number of stratified levels on the Range Chart is an indicator of the degree of the problem.
- Fewer "levels" means less adequate resolution:
- A rule of thumb: There should be approximately 5 levels of resolution between the control limits on the Range Chart and less than 25% of the ranges equal to zero to be considered adequate.
Step 3: Bias
Bias in a measurement study is a "shift" in the pattern on the X-bar chart between operators (i.e., the same part pattern is evident, but one operator reads consistently higher or lower than the others).
Step 4: Measurement Capability
Measurement capability is the comparison of Measurement Variation to Product Variation to determine whether the current measurement process can see part to part differences. More than 50% of the part measurements should be out-of-control to be considered marginally acceptable.
Step 5: Operator Bias
Operator Bias is the comparison of Between-Operator variation to Within-Operator variation. The difference from operator to operator should be less than the variation within operator
Step 6: Operator Inconsistency
Operator Inconsistency is the comparison of Within-Operator variation for a specific operator to the overall Within-Operator variation. Interpretation of the Session Window
What will the gage be used for?
If for Inspection, look at the %Tol
If for Process Improvement, look at the % Study Var
If for SPC, look at ndc
in addition to the % Study Var results.
The Total Gage R&R results are ideally less than 10%, but may be accepted up to 30% depending on the criticality of the characteristic.
ndc should be 5 or greater.
There is additional information that may be gleaned from the results, but these are the important results.