1 / 48

RC Metrology Consulting

RC Metrology Consulting. rcmetrology@yahoo.com. 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.

minty
Download Presentation

RC Metrology Consulting

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. RC Metrology Consulting rcmetrology@yahoo.com

  2. What does it measure? Know the uncertainty of your CMM using a $10 calculator…

  3. 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…”

  4. Outside the Box

  5. 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

  6. 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…

  7. 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.

  8. 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

  9. 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

  10. 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

  11. 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.”

  12. 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.”

  13. Uncertainty??? • Doesn’t it? • Can’t we? • Right??? • Isn’t it? • Don’t they?

  14. 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%

  15. The True Value is: • Always unknown and unknowable (MSA 3rd edition) • Average value taken from an infinite number of readings.

  16. The Plug Gage Paradox • Tell me what it measures: Outside Diameter. • Caliper (.001”) • Micrometer (.0001”) • Bench micrometer (.00005”) • How many readings (1,3,9,12)

  17. The Plug Gage Paradox • Where do we measure? (on the end or in the center) • What if it’s not round (and it won’t be) • Diameter ????????

  18. The Plug Gage Paradox • Because the measurement definition was not clearly defined we will never be certain of our measured result.

  19. Measurement Definition • Micrometer .0001” • 3 readings each end and middle (Total n=9) • Report 9 reading average, minimum reading, and maximum reading

  20. Standard Deviation • Sigma • Spread of measurement data

  21. Standard Deviation

  22. 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

  23. 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!

  24. 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

  25. 1” Sphere results • 75 reading ave = .999878” • 1 Sigma = .000088” • 68% .999790” – .999966” • 95% .999702 – 1.000054” • 99.97% .999614 – 1.000142”

  26. The Histogram

  27. Use the Histogram

  28. Play the Odds

  29. 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?

  30. Concentricity of a Perfect Part

  31. 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

  32. The Histogram

  33. 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”)

  34. Another Look !

  35. Uncertainty??? • Can’t we just??? and then just say… • Dropped parts • Can’t we just ignore gravity????

  36. The Myth of “True” Position

  37. The Myth of “True” Position

  38. The Myth of “True” Position

  39. Define the Measurement

  40. 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

  41. 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”)

  42. .00092”

  43. .0015” 95% 95% .0003”

  44. 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

  45. 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

  46. 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.

  47. 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

More Related