measurement systems analysis€¦ · reproducibility: consistency of measurement results from...

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© 2014 Institute of Industrial Engineers

Chapter 2-5

Measurement Systems

Analysis

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ANALYZE

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MEASURE

2-5-1

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© 2014 Institute of Industrial Engineers 2-5-2

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Less Sophisticated Measures?

2-5-3

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Measurement System Error

Data must be accurate.

All data have measurement errors.

Measurement errors come from primarily two sources:

Measurement equipment (Repeatability)

Measurement individual (Reproducibility)

Gage Repeatability and Reproducibility

(Gage R & R)

Can multiple data collectors using multiple measurement

equipment get the “same” results every time? And if not, is the

difference due to the equipment, the people, or error?

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Measurement Variation Control

Determine variation components.

1. Product variation

2. Equipment variation

3. Appraiser variation

Analyze results.

Specify corrective action.

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Precision vs Accuracy

Accuracy Problems – Not Centered on

Target

Calibration problem

Precision Problems – Too Much

Variation

Equipment Problem

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Accurate & Precise

2-5-7

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Accurate but not Precise

2-5-8

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Precise but Not Accurate

2-5-9

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Neither Accurate nor Precise

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Gage R & R assumes that neither of the last 2 conditions exist in the system being studied (Precise but not accurate and Neither accurate nor precise).

That is, Gage R & R Assumes Gage is Calibrated

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Precision components of Gage R & R:

Repeatability: Ability of the same measurement individual to get consistent measurements

Reproducibility: Consistency of measurement results from person to person when measuring the same part.

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General Suggestions for the Gage Study

Study involves using the gage to measure multiple parts by multiple appraisers in multiple randomized part sequence trials.

10 parts, 2 or 3 appraisers and two or three trials is considered optimal

Analysis of variance can be

performed. SPC XL uses

ANOVA

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Gage Study Example

Data collected for 5 gages (1,2,3,4,5) measured 3 times(Trial 1, Trial 2 and Trial 3) by two appraisers (A,B).

Trial 1 Sequence=4,5,2,1,3



Randomized

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Gage Study Data Example

Appraiser 1 Appraiser 2

Trial 1 Trial 2 Trial 3 Trial 1 Trial 2 Trial 3

Gage 1 0.34 0.42 0.38 0.28 0.32 0.24

Gage 2 0.50 0.56 0.48 0.54 0.48 0.44

Gage 3 0.42 0.46 0.40 0.38 0.42 0.34

Gage 4 0.44 0.48 0.38 0.46 0.44 0.40

Gage 5 0.26 0.30 0.28 0.30 0.28 0.36

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Use SPC XL, MSA (gage capability),

Create MSA Template


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Enter the Data in the SPC XL MSA Template


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Use SPC XL, MSA (gage capability), ANOVA Analysis on the completed MSA Template


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Completed ANOVA for MSA


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Explore Additional Analyses on the Excel

Tabs

MSA- Operator by Part

MSA- Sig Product by Sig Total

MSA- Measurement Pareto

MSA- Xbar Chart

MSA- Range Chart


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Homework Assignments

Project

Problem Set 2 on the class web

site


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