Intro to Measurement System Analysis (MSA)

Intro to Measurement System Analysis (MSA)

• 1.
  By Mark Harrisonfor 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 andPrecision 9/23/2021 Author: Mark D. Harrison 3 Best Worst
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  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
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  Alpha and BetaRisks Part Good Part Bad Scrap Good Part Pass Bad Part
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  Measurements Affect Processes
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  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
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  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”
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  MSA Parameters Gage R&R
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  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
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  What makes agood Gage?
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  Gage Performance Curves
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  Process Capability Dueto Gage R&R 9/23/2021 Author: Mark D. Harrison 13 10% or better Gage R&R is accepted standard for performance Common Cause Variability Contributor
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  How is aGage 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 …
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  Gage R&R Performance Operatorsare switched on each measurement so all variability is captured
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  Gage R&R RangeMethod  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
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  Range Method -Data
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  Range Method -by Appraiser
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  Range Method -Range Chart
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  Range Method -Analysis
• 21.
  Gage R&R Avgand 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
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  Gage R&R Avgand Range Method
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  Gage R&R Anova
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  Gage R&R ANOVAby Part
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  Gage R&R ANOVAby Operator
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  Gage R&R ANOVAby Data
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  Gage R&R ANOVAXbar Chart
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  Gage R&R ANOVAPart*Oper
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  Modern and OlderMeasurement 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