RC Metrology Consulting

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# RC Metrology Consulting - PowerPoint PPT Presentation

RC Metrology Consulting. [email protected] What does it measure?. Know the un certainty of your CMM using a \$10 calculator…. Outside the Box. “So we fix our eyes not on what is seen, but on what is unseen. For what is seen is temporary, but what is unseen is eternal…”. Outside the Box.

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### RC Metrology Consulting

[email protected]

### What does it measure?

Know the uncertainty of your CMM using a \$10 calculator…

Outside the Box
• “So we fix our eyes not on what is seen, but on what is unseen. For what is seen is temporary, but what is unseen is eternal…”
Outside the Box
• 1 + 3 = 2²
• 1 + 3 + 5 = 3²
• 1 + 3 + 5 + 7 = 4²
• 1 + 3 + 5 + 7 + 9 = 5²
• 1 + 3 + 5 + 7 + 9 + 11 = 6²
• 1 + 3 + 5 + 7 + 9 + 11 + 13 = 7²
• 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 = 8²
• 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 = 9²
• 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 = 10²
CMM game plan
• Order it up…
• We will establish a strategic, easy to implement, statistical system to learn the certainty of any given CMM application
• Plan, Do, Check, Action…
Our Goal
• To improve the measurement capability of our CMM by increasing the certainty of the measurements we are making.
• This improvement may seem to be very small.
Small Improvements
• The difference between a career in the Minor Leagues and the Baseball Hall of Fame is only 1 more hit per week.
• A Baseball season is played April – September = 26 weeks
The Minor Leagues
• In a normal season a player will encounter 500 at-bats.
• 125 hits in 500 at-bats…
• 125 / 500 = .250 batting average.
• Toledo Mudhens
Imagine if ???
• If a player could get just 1 more hit per week…
• 151 hits in 500 at-bats…
• 151 / 500 = .302 batting average.
• The Hall of Fame
Uncertainty???
• ISO-9000, QS-9000:1994, state: “Inspection measurement and test equipment shall be used in a manner which ensures that the measurement uncertainty is known and consistent with the required measurement capability.”
Uncertainty???
• TS-16949: Recommends internal inspection labs comply with ISO/IEC17025…“When estimating the uncertainty of a measurement, all uncertainty components which are of importance in the given situation shall be taken into account using appropriate statistical methods of analysis.”
Uncertainty???
• Doesn’t it?
• Can’t we?
• Right???
• Isn’t it?
• Don’t they?
Uncertainty is:
• The upper estimated limit of how wrong a given reading (or value) can be.
• Kerry 53% Bush 47% (±4%)
• Kerry 57% Bush 43%
• Bush 51% Kerry 49%
The True Value is:
• Always unknown and unknowable (MSA 3rd edition)
• Average value taken from an infinite number of readings.
• Tell me what it measures: Outside Diameter.
• Caliper (.001”)
• Micrometer (.0001”)
• Bench micrometer (.00005”)
• Where do we measure? (on the end or in the center)
• What if it’s not round (and it won’t be)
• Diameter ????????
• Because the measurement definition was not clearly defined we will never be certain of our measured result.
Measurement Definition
• Micrometer .0001”
• 3 readings each end and middle (Total n=9)
Standard Deviation
• Sigma
Sample Data Collection
• Must be RANDOM
• Attempt to represent the entire population
• The sample will always be a sample and display less variation than the population
Sample and Population
• Clock cars in a designated 45mph speed limit zone
• 6 hours / 1 week = Ave, min, and max
• 24 hrs / 4 weeks = Ave, min, and max
• 120 hrs / 26 weeks = Wow!
Probe calibration controversy
• Define the measurement
• Probe 9 points on 1” master sphere: 8 points around equator and 1 point on north pole
• 3 measurements / 25 days
1” Sphere results
• 75 reading ave = .999878”
• 1 Sigma = .000088”
• 68% .999790” – .999966”
• 95% .999702 – 1.000054”
• 99.97% .999614 – 1.000142”
CMM game plan
• Before we start measuring our parts we can measure the 1” master sphere 3 times and compare our results to our Histogram.
• Do we want to order it up?
Define the Measurement
• 5 point XY Baseplane
• 12 point Cylinder as Z axis
• 9 point Circle (bottom) as XY origin and Datum
• 9 point Circle (top) as feature
• 3 measurements / 25 days
Ring gage concentricity
• 75 reading ave = .00015”
• 1 Sigma = .00009”
• 47.5% of the time (or + 2 sigma) it measured worse than .00015” (or as high as .00024”)
Uncertainty???
• Can’t we just??? and then just say…
• Dropped parts
• Can’t we just ignore gravity????
Define the Measurement
• 7 point XY Baseplane
• 5 point X axis line
• 5 Point Y axis line
• XY origin at intersection
• 9 point circle (Z -.100”)
• 3 measurements / 25 days
Where is the center???
• Average .00092”
• 1 sigma of .00030”
• 68% of the time our value obtained was between .0006” and .0012” (.0006”)
• 95% of the time our value obtained was between .0003” and .0015“ (.0012”)
.0015”

95%

95%

.0003”

References and Acknowledgements
• MSA 3rd Edition by AIAG
• Mitutoyo of America
• Cliff’s Quick Review - Algebra, Statistics, and Geometry
• ASME Y14.5-1994 Geometric Dimensioning and Tolerancing
• H.E.S. Honda Engineering Specifications
• DCC CMM Programming - Part Alignment and Vector Points by Scott Beavers
References and Acknowledgements
• Technical Shop Math by John G. Anderson
• Tooling and Production Magazine
• Modern Machine Shop Magazine
• Cybermetrics: GAGEtrak software
• NWCI Calibration and Inspection
• Nelson Precision - A Mitutoyo Company
• Qualtech Tool and Engineering
• Hower Tool - Ossian, Indiana
References and Acknowledgements
• NWE/Foxconn - Santa Clara, CA
• Mitutoyo of America
• SFC (Retired) Thomas J. Ravenell, Ft. Bragg, NC
• Dave Schwab - Nelson Precision
• Terry Davis - Mitutoyo
• Mike Dukehart - Mitutoyo
• Jerry Guffy - Mitutoyo
• James Vannoy - CMM Technology, Inc.
References and Acknowledgements
• Scott Beavers - CMM Resources
• Travis East - Geometry 2.8 Freeware
• Dr. Bill McNeese
• Dr. Henrik S. Nielsen
• Gordan Skattum
• My Wife, Ramona