# Interpreting and Improving a Measurement System

## Which component dominates?

| Dominant component | Typical causes | Fixes |
|--------------------|----------------|-------|
| Repeatability (EV) | Gauge wear or play, poor fixturing, part positioning, resolution, temperature, dirty surfaces | Fixture, repair or replace gauge, better resolution, clean, control temperature, average several readings |
| Reproducibility (AV) | Different methods, training, reading technique (parallax), force on hand gauges | Standardise method in a WI with photos, train, fixture to remove technique, digital readout |
| Interaction (operator x part) | Some operators struggle with some parts (size, shape, access) | Find the parts; improve access or method for them |
| Part variation too small (low ndc) | Parts chosen from a narrow range | Re-run with parts spanning the process range |

## Resolution rule

Gauge resolution should be 1/10 of the tolerance or better. A gauge reading to 0.01 mm on a 0.018 mm tolerance
gives at most 2 distinct readings across the tolerance: no study can rescue it.

## Attribute systems

| Problem | Fix |
|---------|-----|
| High miss rate (bad parts accepted) | Boundary samples (limit samples) at the station, better lighting / magnification, go/no-go fixture, automatic inspection |
| High false alarm (good parts rejected) | Clear acceptance criteria with photos, training on boundary samples |
| Low within-appraiser agreement | Fatigue, unclear criteria, too-fast pace: shorten inspection periods, define criteria |
| One appraiser poor | Retrain and re-qualify before inspecting again |

## After improvement

Re-run the study with the same design and compare. Record MSA results for each gauge used in the control plan
(IATF 7.1.5.1.1) and repeat them after gauge repair, relocation or a change in method.