Gauge R&R

Gauge R&R is a term used in MSA (Measurement System Analysis). It generates confidence in the overall measurement system. Confidence is required to establish that measurement system is capable enough in distinguishing Good and Bad parts.

What is Measurement System:

Major constituents of Measurement system are Inspector, Gauge/Instrument and Parts. All three plays a vital role in establishing the health of the system.

Why gauge R&R?

Gauge R&R results ensures that whatever Measurement system we are using is capable enough to capture even border line cases e.g. Checking a Diameter of 20.000 ± 0.008mm through Micrometer of L.C. 0.001mm. Can we be sure that part having diameter 20.009 will get captured by the system or   part having Diameter 19.992 will be accepted or rejected by Measurement system?

Variations in measurement system:

Appraiser variation is a major source of variation in a measurement system. Appraiser to appraiser observations varies and to minimise this and establishing the variation data Gauge R&R stuady is done.

How to do?

  1. Select 10 samples. Mark them 1 to 10. Check samples must represent whole tolerance band and must include reject parts also. Try to include border line accepted or rejected parts also.
  2. Take the instrument to be used for inspection. Check– Instrument must be calibrated.
  3. Minimum 2 appraisers required for study and one Study Driver. Check– None of the appraisers should know the measurement results of 10 parts taken.
  4. Give one part to appraiser 1 and note down the reading. Give all the parts randomly one by one. Check- keep Appraiser 2 out of this to eliminate the Bias in his measurement. Check- Always give parts randomly so that Appraiser do try to remember the readings.
  5. Repeat Step 4 with Appraiser 2.
  6. Repeat steps 4 & 5 two more times.
  7. Put the data in the Gauge R&R data sheet or Minitab.
  8. If R&R is <10% and ndc >5 measurement system is capable enough.
  9. If R&R is >10% and <20% and ndc >5 measurement system requires modifications. Like training of appraisers, Check instrument calibration etc..
  10. If R&R is >30% and ndc >5 measurement system is not capable enough and should be replaced.
  11. If ndc

 

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