Six Sigma Quality Engineering

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Six Sigma Quality Engineering

• Week 5
• Chapters 5 (Measure Phase)

Variable Gauge RR
Data is only as good as the system that measures
it. If you cant measure it, you cant manage
it.
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The Science of Measurement
I often say that when you measure what you are
speaking about and express it in numbers, you
know something about it. LORD KELVIN,
1891 He clearly stressed that little progress
is possible in any field of investigation without
the ability to measure. The progress of
measurement is, in fact, the progress of science.

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Objectives

• Measurement Systems Analysis
• Key Terminology
• Variable Gauge RR
• A tool for estimating measurement system error
• How to conduct a gauge RR
• Minitab Output
• Gauge R R Study Exercise

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Definitions

• Variable Data
• Continuous measurements such as length, voltage,
  viscosity
• Repeatability
• Variation in measurements obtained with one gage
  when used several times by one appraiser.
• Reproducibility
• Variation in the average of the measurements made
  by different appraisers using the same
  measurement system.

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What is GRR?

• Measurement Systems Analysis

How good is our measurement system?
?2T ?2p ?2m
?2T Total Variance ?2p Process
Variance ?2m Measurement Variance
GRRRRRRR!!!
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Possible Source of Variation
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Types of Measurement Error that Affect Location
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Types of Measurement Error that Affect Spread
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Gauge RR Allows Control of the Measurement System
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Variable Gauge RR - Whats Involved?
3 Appraisers
1 Gauge
10 Parts
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How to set up a Variable GRR Study

• Preparation Planning
• 1 Gauge
• 3 Operators (Appraisers)
• 10 Parts
• 3 Trials
• Randomize the readings
• Code the parts (blind study) if possible
• 3 Ops x 10 parts x 3 trails 90 Data Points
• 4 Ops x 10 parts x 3 trails 120 Data Points

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Minitab Gage RR Graphical Output
The number of distinct categories of parts that
the process is currently able to distinguish
(Must distinguish at least 5 types of parts)
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Acceptability Criteria

• RR Indices
• ? 10 Acceptable Measurement System
• 10 - 30 May be acceptable based upon
  application, cost of measurement device, cost
  of repair, etc.
• ? 30 Not acceptable. Measurement system
  needs improvement.
• Number of Distinct Categories Index
• 1 Unacceptable. One part cannot be
  distinguished form another.
• 2 -4 Generally unacceptable
• ? 5 Recommended

Module 0025
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Minitab Gage RR Graphical Output
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Minitab Gage RR Graphical Output
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Minitab Gage RR Graphical Output
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Minitab Gage RR Statistical Output
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Minitab Gage RR Statistical Output
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Questions? Comments?