Co Ordinate Measuring Machine

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  • CoordinateMeasuringMachine(CMM)

    ME0403MetrologyandQualityControl

  • ComplexJobstobemeasured

  • ComplexJobstobemeasured

  • ComplexJobstobemeasured

  • Tomeasuretheactualsizeofw/pcomparisonwithdesiredshapeandevaluationofmetrologicalinformationsuchas

    Size Form Location Position

    Actualsizeisobtainedbyprobingthesurfaceatdiscretemeasuringpoints.Everyptisexpressedintermsofitsx,y,z coordinates

    FunctionsofCMM

  • MechanicalSetupwith3axesmovement&thedisplacementtransducer

    Probeheadtoprobetheworkpieceinaspatialdirection

    ControlUnit Computerwithsoftwaretocalculate&representtheresults

    CMMsystemcomponents

  • MechanicalSetup

  • Beingnoncontact,airbearingsavoidthetraditionalbearingrelatedproblemsoffriction,wear,andlubricanthandling,andofferdistinctadvantagesinprecisionpositioningandhighspeedapplications.

    AirBearing

  • Thefluidfilmofthebearingisachievedbysupplyingaflowofairthroughthebearingitselftothebearingsurface.

    Numerousbearingdesignsexisttoensureuniformpressureisdistributedacrosstheentirebearingarea.

    Thedesignoftheairbearingissuchthat,althoughtheairconstantlydissipatesfromthebearingsite,thecontinualflowofpressurizedairthroughthebearingissufficienttosupporttheworkingloads.

    AirBearing

  • ProbesandProbeHead

  • TouchTriggerprobe

  • ProbeChangingSystem

  • Step1:HometheCMM establishesglobalcoordinatesystem(Xm,Ym,Zm)

    Step2:QualifytheTip(Calibrationofprobetipwithrespecttoprobehead) compensatesfortipdiameter

    Step3:AlignthePart establishesalocalcoordinatesystemonthepart(Xw,Yw,Zw)

    Step4:MeasurethePart Step5:Representationofmeasurementresultsaftercoordinatetransformationintow/prelatedcoordinatessystem

    Programming/MeasurementwiththeCMM

  • Movingbridge Fixedbridge Cantilever Gantry

    TypesofCMM

  • CantileverCMM(Manual)

  • FixedBridgeCMM

  • MovingBridgeCMM(ComputerControlled)

  • GantryTypeCMM

  • MeasuringRanges

    18.11"x18.11"x11.81"(460x460x300mm)40.20"x32.20"x24.21"(1021x818x615mm)

  • SourcesoferrorsinCMMmeasurementsspatialerrorscomputationalerrors.

    Spatialerrors areerrorsinthemeasuredpositionofapointonthesurfaceoftheWorkpiece

    Computationalerrors aretheerrorsintheestimateddimensionsandformdeviationsoftheworkpiece

    PotentialSourcesofCMMError

    http://coordinate-measuring-machine.net/cmm-sources-of-error-e/13/
  • TheaccuracyofthecomponentsoftheCMM theguideways,thescales,theprobesystemandthequalificationsphere.

    TheenvironmentinwhichtheCMMoperates theambienttemperature,temperaturegradients,humidityandvibration.

    Theprobingstrategyused themagnitudeanddirectionoftheprobeforce,thetypeofprobestylususedandthemeasuringspeedoftheprobe.

    Thecharacteristicsoftheworkpiece elasticity,surfaceroughness,hardnessandthemassofthecomponent.

    SpatialErrors

  • TheCMMsoftwareusedtoestimatethegeometryoftheworkpiece.

    TheprecisionofthecomputerusedontheCMM.

    Thenumberandrelativepositionofthemeasuredpoints.

    Theextenttowhichthegeometrydepartsfromtheidealgeometricform.

    Computationalerrors

    Co ordinate Measuring Machine(CMM)Complex Jobs to be measured Complex Jobs to be measured Complex Jobs to be measured Functions of CMMCMM system componentsMechanical Set upAir BearingAir BearingProbes and Probe HeadTouch Trigger probeProbe Changing SystemProgramming/Measurement with the CMMTypes of CMMCantilever CMM( Manual)Fixed Bridge CMMMoving Bridge CMM( Computer Controlled)Gantry Type CMMMeasuring RangesPotential Sources of CMM ErrorSpatial ErrorsComputational errors