22
Engineering Drawings: Geometric Tolerancing A short series of lectures on Engineering Drawing as Part of MECH2400 5400: Mechanical Design 1 By Paul Briozzo

Engineering Drawings Lecture Linear Geometric Tolerancing.pdf

  • Upload
    ijabi

  • View
    47

  • Download
    0

Embed Size (px)

Citation preview

  • EngineeringDrawings:GeometricTolerancing

    AshortseriesoflecturesonEngineeringDrawingasPartofMECH24005400:MechanicalDesign1ByPaulBriozzo

  • DistortedObjectsbySuzyLelievre

    ScaleTransformSALOMEGeometryUsersGuide:ScaleTransform

    GeometricTolerancing

  • GeometricTolerancingWhatisit?

  • GeometricTolerancing UnlikeDimensionalTolerancethatconcernsitselfwithsizecontrol,

    GeometricTolerancing concernsitselfwithshapecontrol

    GeometricTolerancing influencesthemanufacturingandinspectionprocesschosen

    GeometricTolerancing isrequiredinfeaturesinindustriessuchas Aerospacecomponentmanufacture Automobilecomponentmanufacture Precisionmachinerymanufacture Biomedicalcomponentmanufacture

    GeometricTolerancing isusedwherehighinterchangeofpartsisrequired

    GeometricTolerancing andDimensionalTolerancing arelinked

  • BasicConceptsofGeometryTolerancing

    GeometryTolerancesarespecifiedaccordingtofunctionalrequirements:Useitifitisneeded,ifnotDONOTasitaddstotheexpenseofthemanufacture,inspectionofacomponentandclarityofanengineeringdrawing.

    Dependingonthefeaturetobetoleranced andthewayinwhichitisdimensioned,thetolerancezonewillbeoneof: Thespacebetweentwoparallellines Thespacewithinacircle Thespacebetweentwoconcentriccircles Thespacewithinacylinder Thespacebetweentwocoaxialcylinders Thespacebetweentwoequidistantsurfaces Thespacewithinasphere

  • GeometryTolerancing SymbolicStructure

  • InterpretationofGeometryTolerancingFlatness

    AFlatnesstoleranceisusedtocontroltheflatnessofasurface.Thetolerancezoneisaspecifiedspaceseparatingtwoparallelplanesbetweenwhichthesurfacetobecontrolledmustlie.

  • Straightness Astraightnesstolerancemaybeusedtocontrol:

    1.Straightnessofaline 2.Straightnessofanaxisinasingleplane 3.Straightnessoftheaxesofsolidsofrevolution

  • Perpendicularity Aperpendicularity toleranceisusedtocontrol:

    1.alinewithrespecttoadatumline 2.anaxiswithrespecttoadatumplane

  • 3.asurfacewithrespecttoadatumaxis 4.asurfacewithrespecttoadatumplane

  • Position Apositiontoleranceisusedtocontrolthelocationofafeatureby

    limitingitsdeviationfromaspecifiedtrueposition. 1.aholeaxis 2.asurface

  • Position(Concentricity) Aconcentricitytoleranceisusedtocontrolaconditioninwhich

    twoormorefeaturessuchascircles,spherescylinders,conesorhexagonsarerequiredtoshareacommoncentreoraxis

  • CaseStudy QantasA380OilStubPipeLatein2010,aQantasA380sufferedacatastrophicfailureofoneofitsfourmainRollsRoyceengines.Investigationspointtoafailureinanoilstubpipecausedbyamanufacturingdefect.

  • Position(Symmetry) Asymmetrytoleranceisusedtocontrolaconditioninwhichoneormore

    featuresaresymmetricallydisposedeithersideofacentreline(axis)orcentreplane(median)ofanotherfeaturewhichisspecifiedasthedatum.

  • Cylindricity Acylindricity tolerancespecifiesatolerancezoneconsistingofanannularspacebetween

    twocoaxialcylindershavingadifferenceinradiiequaltothespecifiedtolerance.

  • Angularity Anangularitytoleranceisusedtocontrolangularrelationshipsofanyanglebetween

    straightline(axes)orsurfaceswithstraightlineelementssuchasflatorcylindricalsurfaces

  • Circularity Acircularitytolerancespecifiesthewidthofanannulartolerancezone,boundedbytwo

    concentriccirclesinthesameplanewithinwhichthecircumferenceofthefeaturemustlie.

  • Parallelism Aparallelismtoleranceisusedtocontroltheorientationoffeaturesrelatedtooneanother

    byanangleofzerodegrees.

  • Example(ABadOne)

  • EffectsofCombiningLinearandGeometricTolerances

    Intolerancing featuresofsizeonmatingcomponentswhereeaseofassemblyisimportant,itshouldberealisedthattheleastfavourableconditionforassemblyoccurswhenmatingsizesarethemaximummaterialsizeallowablebytheindividualtoleranceofeachcomponent.

    Greatervariationsinshapegeometrycanbeacceptedasthematingsizesapproachtheirleastmaterialsize.

  • VirtualSize Virtualsizereferstothedimensionoftheoverallenvelopeofperfectformwhichtouchesthe

    highestpointsofafeature.

    Forashaft,itisthemaximummeasuredsizeplustheactualeffectofformvariationssuchasflatness,straightness,roundness,cylindricity andprofile.

    Forahole,itistheminimummeasuredsizeminustheactualeffectofformvariationssuchasflatness,straightness,roundness,cylindricity andprofile.

  • InterpretthisExampleofGeometricTolerancing