Intro to MSA. Basic purpose and guidelines on qualifying and testing measurement systems typically used in manufacturing and R&D.

1. By Mark Harrison for ASQ Section 1112 20 April 2021

2. What is MSA / Gage R & R
 An objective process used to quantify a measurement
system for the primary components of:
Accuracy – is the measurement the correct value?
Precision – what is the smallest resolution obtained?
Stability – how consistent are the values over time?

3. Metrology Accuracy and Precision
9/23/2021 Author: Mark D. Harrison 3
Best
Worst

4. Measurements Affect Processes
 Measurement variability contributes to process
variability
 Process Capability indexes are reduced
 Alpha and Beta risks are increased
Alpha : Risk of Scrapping a Good Part
Beta : Risk of Accepting a Bad Part

5. Alpha and Beta Risks
Part Good Part Bad
Scrap Good Part
Pass Bad Part

6. Measurements Affect Processes

7. When is MSA / Gage R & R Used ?
 Initial instrument installation and qualification
 Determination of use with a current/new process
 Qualification of the instrument after repair/upgrade
 Replacement or introduction of new standard

8. MSA Parameters
 Accuracy – Value vs Standard
 Bias – difference between Value and Observed Average
 Stability – change in Value over Time
 Linearity – difference of Bias thru operation range
 Precision – variations from gages, people, conditions…
 Repeatability – “within appraiser/system”
 Reproducibility – “between appraiser/system”

9. MSA Parameters
Gage R&R

10. Gage R & R
 Gage R & R looks at a subset of MSA
 Repeatability - “within appraiser”
One instrument used several times
One appraiser
One part
 Reproducibility “between appraisers”
One instrument used several times
Different appraisers
Same part

11. What makes a good Gage?

12. Gage Performance Curves

13. Process Capability Due to Gage R&R
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10% or better Gage R&R is
accepted standard for performance
Common Cause
Variability Contributor

14. How is a Gage R&R Performed?
 Need:
One Instrument
2-3 Operators
5-10 Parts labeled/numbered clearly from the same
process/specs
 Perform/Record Measurements:
Operator 1 / Part 1
Operator 2 / Part 1
Operator 3 / Part 1
Operator 1 / Part 2
Operator 2 / Part 2
Operator 3 / Part 2 …

15. Gage R&R Performance
Operators are switched on each measurement so all variability is captured

16. Gage R&R Range Method
 Quick overall approximation of measurement
variability
 Repeatability and Reproducibility not determined
 Verifies that Gage R&R has not changed
 Typically 2 appraisers and 5 parts are used

17. Range Method - Data

18. Range Method - by Appraiser

19. Range Method - Range Chart

20. Range Method - Analysis

21. Gage R&R Avg and Range Method
 From AIAG
 Manual or Excel process
 Analysis similar to ANOVA outputs
 Most MSA / Gage R&R done on computers using
ANOVA methodology
 Worksheet shown as example

22. Gage R&R Avg and Range Method

23. Gage R&R Anova

24. Gage R&R ANOVA by Part

25. Gage R&R ANOVA by Operator

26. Gage R&R ANOVA by Data

27. Gage R&R ANOVA Xbar Chart

28. Gage R&R ANOVA Part*Oper

29. Modern and Older Measurement
System Characteristics
Modern Gages Older Gages
 Solid State (MEMS, Laser)
 Automated positioning
 Digital Computing/Output
 Operating Robustness
 Mechanical (Springs, Dials)
 Manual Positioning
 Manual Reading
 Affected by Environment

30. Common Gage Improvements
 Fixturing
Ensure part to be measured is located properly
 Vibration Table
Eliminate / reduce effects of nearby manufacturing equipment
 Environmental Controls
Temperature / Humidity / Measurement Room
 Operator Training / Resources
Procedures / Lights / Magnifying Glass, etc…
 Gage / Technology upgrade
New Technology more capable / Robust

31. MSA Documentation
 SixSigmaStudyGuide.com
 AIAG Measurement Systems Analysis Book