RC Metrology Consulting [email protected]. What does it measure? Know the uncertainty of your...

RC Metrology RC Metrology ConsultingConsulting

[email protected]@yahoo.com

What What does it does it

measure?measure?Know the Know the ununcertainty of your certainty of your CMM using a $10 calculator…CMM using a $10 calculator…

Outside the BoxOutside the Box““So we fix our eyes So we fix our eyes not on what is seen, not on what is seen, but on what is unseen. but on what is unseen. For what is seen is For what is seen is temporary, but what temporary, but what is unseen is eternal…”is unseen is eternal…”

Outside the BoxOutside the Box

Outside the BoxOutside 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 planCMM game planOrder it up…Order it up…We will establish a strategic, We will establish a strategic,

easy to implement, statistical easy to implement, statistical system to learn the certainty system to learn the certainty of any given CMM applicationof any given CMM application

Plan, Do, Check, Action…Plan, Do, Check, Action…

Our Goal Our Goal To improve the measurement To improve the measurement

capability of our CMM by capability of our CMM by increasing the certainty of the increasing the certainty of the measurements we are measurements we are making.making.

This improvement may seem This improvement may seem to be very small.to be very small.

Small Improvements Small Improvements The difference between a The difference between a

career in the Minor Leagues career in the Minor Leagues and the Baseball Hall of Fame and the Baseball Hall of Fame is only 1 more hit per week.is only 1 more hit per week.

A Baseball season is played A Baseball season is played April – September = 26 weeksApril – September = 26 weeks

The Minor Leagues The Minor Leagues In a normal season a player In a normal season a player

will encounter 500 at-bats.will encounter 500 at-bats.125 hits in 500 at-bats…125 hits in 500 at-bats…125 / 500 = .250 batting 125 / 500 = .250 batting

average.average.Toledo MudhensToledo Mudhens

Imagine if ??? Imagine if ??? If a player could get just 1 If a player could get just 1

more hit per week…more hit per week…151 hits in 500 at-bats…151 hits in 500 at-bats…151 / 500 = .302 batting 151 / 500 = .302 batting

average.average.The Hall of FameThe Hall of Fame

Uncertainty???Uncertainty??? ISO-9000, QS-9000:1994, state: ISO-9000, QS-9000:1994, state:

“Inspection measurement and test “Inspection measurement and test equipment shall be used in a equipment shall be used in a manner which ensures that the manner which ensures that the measurement uncertainty is known measurement uncertainty is known and consistent with the required and consistent with the required measurement capabilitymeasurement capability.”.”

Uncertainty???Uncertainty??? TS-16949: Recommends internal TS-16949: Recommends internal

inspection labs comply with ISO/IECinspection labs comply with ISO/IEC 17025…17025… “When estimating the “When estimating the uncertainty of a measurement, uncertainty of a measurement, all all uncertainty components which are uncertainty components which are of importance in the given situation of importance in the given situation shall be taken into accountshall be taken into account using using appropriate statistical methods of appropriate statistical methods of analysis.”analysis.”

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

Uncertainty is:Uncertainty is:The upper estimated limit of The upper estimated limit of

how wrong a given reading how wrong a given reading (or value) can be.(or value) can be.

Kerry 53% Bush 47% (±4%)Kerry 53% Bush 47% (±4%)Kerry 57% Bush 43%Kerry 57% Bush 43%Bush 51% Kerry 49%Bush 51% Kerry 49%

The The TrueTrue Value is: Value is:Always unknown and Always unknown and

unknowable unknowable (MSA 3(MSA 3rdrd edition) edition)

Average value taken from an Average value taken from an infinite number of readings.infinite number of readings.

The Plug Gage The Plug Gage ParadoxParadox

Tell me what it measures: Tell me what it measures: Outside Diameter.Outside Diameter.

Caliper (.001”)Caliper (.001”) Micrometer (.0001”)Micrometer (.0001”) Bench micrometer (.00005”)Bench micrometer (.00005”) How many readings (1,3,9,12)How many readings (1,3,9,12)


Where do we measure? (on Where do we measure? (on the end or in the center)the end or in the center)

What if it’s not round (and it What if it’s not round (and it won’t be)won’t be)

Diameter ????????Diameter ????????


Because the measurement Because the measurement definition was not clearly definition was not clearly defined we will never be defined we will never be certain of our measured certain of our measured result.result.

Measurement Measurement DefinitionDefinition

Micrometer .0001”Micrometer .0001”3 readings each end and 3 readings each end and

middle (Total n=9)middle (Total n=9)Report 9 reading average, Report 9 reading average,

minimum reading, and minimum reading, and maximum readingmaximum reading

Standard DeviationStandard DeviationSigmaSigmaSpread of measurement dataSpread of measurement data

Standard DeviationStandard Deviation

Sample Data Sample Data CollectionCollection

Must be RANDOMMust be RANDOMAttempt to represent the Attempt to represent the

entire populationentire populationThe sample will always be a The sample will always be a

sample and display less sample and display less variation than the populationvariation than the population

Sample and Sample and PopulationPopulationClock cars in a designated Clock cars in a designated

45mph speed limit zone45mph speed limit zone6 hours / 1 week = Ave, min, 6 hours / 1 week = Ave, min,

and maxand max24 hrs / 4 weeks = Ave, min, 24 hrs / 4 weeks = Ave, min,

and maxand max120 hrs / 26 weeks = Wow!120 hrs / 26 weeks = Wow!

Probe calibration Probe calibration controversycontroversy

Define the measurementDefine the measurementProbe 9 points on 1” master Probe 9 points on 1” master

sphere: 8 points around sphere: 8 points around equator and 1 point on north equator and 1 point on north polepole

3 measurements / 25 days3 measurements / 25 days

1” Sphere results1” Sphere results75 reading ave = .999878”75 reading ave = .999878”1 Sigma = .000088”1 Sigma = .000088”68% .999790” – .999966”68% .999790” – .999966”95% .999702 – 1.000054”95% .999702 – 1.000054”99.97% .999614 – 1.000142”99.97% .999614 – 1.000142”

The HistogramThe Histogram

0

2

4

6

8

10

12

14

16

18

20

0.99950 0.99960 0.99970 0.99980 0.99990 1.00000 1.00010 1.00020

Measurement

Use the HistogramUse the Histogram

0

2

4

6

8

10

12

14

16

18

20

0.99950 0.99960 0.99970 0.99980 0.99990 1.00000 1.00010 1.00020

Measurement

Play the OddsPlay the Odds

0

2

4

6

8

10

12

14

16

18

20

0.99950 0.99960 0.99970 0.99980 0.99990 1.00000 1.00010 1.00020

Measurement

CMM game planCMM game planBefore we start measuring Before we start measuring

our parts we can measure our parts we can measure the 1” master sphere 3 times the 1” master sphere 3 times and compare our results to and compare our results to our Histogram.our Histogram.

Do we want to Do we want to order it up?order it up?

Concentricity of a Perfect Concentricity of a Perfect PartPart

Define the MeasurementDefine the Measurement5 point XY Baseplane5 point XY Baseplane12 point Cylinder as Z axis12 point Cylinder as Z axis9 point Circle (bottom) as XY 9 point Circle (bottom) as XY

origin and Datumorigin and Datum9 point Circle (top) as feature9 point Circle (top) as feature3 measurements / 25 days3 measurements / 25 days

The HistogramThe Histogram

Ring gage concentricityRing gage concentricity75 reading ave = .00015”75 reading ave = .00015”1 Sigma = .00009” 1 Sigma = .00009” 47.5% of the time (or + 2 47.5% of the time (or + 2

sigma) it measured worse sigma) it measured worse than .00015” (or as high than .00015” (or as high as .00024”)as .00024”)

Another Look !Another Look !

Uncertainty???Uncertainty???Can’t we just??? Can’t we just??? and then just say…and then just say…

Dropped partsDropped partsCan’t we just Can’t we just ignore gravity????ignore gravity????

The Myth of “True” The Myth of “True” PositionPosition

Define the MeasurementDefine the Measurement

Define the MeasurementDefine the Measurement7 point XY Baseplane7 point XY Baseplane5 point X axis line5 point X axis line5 Point Y axis line5 Point Y axis lineXY origin at intersectionXY origin at intersection9 point circle (Z -.100”)9 point circle (Z -.100”)3 measurements / 25 days3 measurements / 25 days

Where is the center???Where is the center??? Average .00092”Average .00092” 1 sigma of .00030”1 sigma of .00030” 68% of the time our value 68% of the time our value

obtained was between .0006” obtained was between .0006” and .0012” (.0006”)and .0012” (.0006”)

95% of the time our value 95% of the time our value obtained was between .0003” obtained was between .0003” and .0015“ (.0012”)and .0015“ (.0012”)

.00092”

95%95%

.0003”

.0015”

References and References and AcknowledgementsAcknowledgements

MSA 3rd Edition MSA 3rd Edition by AIAGby AIAG

Mitutoyo of AmericaMitutoyo of America Cliff’s Quick Review - Algebra, Statistics, Cliff’s Quick Review - Algebra, Statistics,

and Geometryand Geometry ASME Y14.5-1994 ASME Y14.5-1994 Geometric Dimensioning Geometric Dimensioning

and Tolerancingand Tolerancing

H.E.S. Honda Engineering SpecificationsH.E.S. Honda Engineering Specifications DCC CMM Programming - Part Alignment DCC CMM Programming - Part Alignment

and Vector Points and Vector Points by Scott Beaversby Scott Beavers


Technical Shop Math Technical Shop Math by John G. Andersonby John G. Anderson

Tooling and Production MagazineTooling and Production Magazine Modern Machine Shop MagazineModern Machine Shop Magazine Cybermetrics: GAGEtrak softwareCybermetrics: GAGEtrak software NWCI Calibration and InspectionNWCI Calibration and Inspection Nelson Precision - Nelson Precision - A Mitutoyo CompanyA Mitutoyo Company

Qualtech Tool and EngineeringQualtech Tool and Engineering Hower Tool - Ossian, IndianaHower Tool - Ossian, Indiana


NWE/Foxconn - Santa Clara, CANWE/Foxconn - Santa Clara, CA Mitutoyo of AmericaMitutoyo of America SFC (Retired) Thomas J. Ravenell, SFC (Retired) Thomas J. Ravenell,

Ft. Bragg, NCFt. Bragg, NC

Dave Schwab - Dave Schwab - Nelson PrecisionNelson Precision

Terry Davis - Terry Davis - MitutoyoMitutoyo

Mike Dukehart - Mike Dukehart - MitutoyoMitutoyo

Jerry Guffy - Jerry Guffy - MitutoyoMitutoyo

James Vannoy - James Vannoy - CMM Technology, Inc.CMM Technology, Inc.


Scott BeaversScott Beavers - CMM Resources - CMM Resources

Travis East - Travis East - Geometry 2.8 FreewareGeometry 2.8 Freeware

Dr. Bill McNeeseDr. Bill McNeese Dr. Henrik S. NielsenDr. Henrik S. Nielsen Gordan SkattumGordan Skattum My Wife, RamonaMy Wife, Ramona

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