现代数控机床原理与结构.ppt

现代数控机床原理与结构.ppt

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书名：

现代数控机床原理与结构（双语）ISBN：

978-7-111-42403-1作者：

郁元正出版社：

机械工业出版社本书配有电子课件,现代数控机床原理与结构（双语）ppt课件,Chapter2Motions&coordinatesystemofMachinetools,2.1Motionsofmachinetool2.2Machinetooldrive2.3Coordinatesystems,现代数控机床原理与结构（双语）ppt课件,2.1Motionsofmachinetool,2.1.1PurposeofmotionsThepurposeofmachinetoolmotionsistoremovematerialsfromworkpiecestoobtainrequiredshapes,dimensionsandsurfacequality.Motionessentialsaretoolmotions,workpiecemotions,andcuttingmotions.2.1.2SurfaceformingmotionSurfaceformingmotionistherelativecuttingmotionbetweentoolandworkpiece.Typesandquantityofsurfaceformingmotiondetermineshapeofworkpiece,machiningmethodandtoolconstructions,现代数控机床原理与结构（双语）ppt课件,Outercircularsurfaceturning,Surfaceformingmotionconsistsof:

PrimarymotionFeedingmotion,现代数控机床原理与结构（双语）ppt课件,1）PrimarymotionPrimarymotioncausesrelativemotionbetweencuttingtoolandworkpiece,andremovematerialfromworkpiece.Examplesofprimarymotions:

Rotarymotionofworkpiece（turning）Rotarymotionofcuttingtools（drilling,milling,boring）Reciprocatingmotionofcuttingtools（broaching,planing）,Everymachiningprocessmusthave,andonlyhasaprimarymotion.,现代数控机床原理与结构（双语）ppt课件,2）FeedingmotionFeedingmotioncausesansecondaryrelativemotionbetweencuttingtoolandworkpiece,andenablestoolcancontinuouslyremovematerialfromworkpiecetoformadesiredshape.ExamplesoffeedingmotionAxialandradialmotionsofcuttingtool（turning）Stepmotionsofcuttingtoolorworkpiece（planing）,Note:

Feedingmotioncanbeperformedbybothcuttingtoolsorworkpieces;Twoormorefeedingmotionscanco-exist（gearhobbing）;Zerofeedingmotionispossible（broaching）.,现代数控机床原理与结构（双语）ppt课件,Thinking,Identifyprimarymotionsandfeedingmotions.,Planing,Broaching,Milling,现代数控机床原理与结构（双语）ppt课件,2.1.3AssistantmotionsAllmotionsotherthansurfaceformingmotions,includingplungemotion,indexingmotion,alignmentmotion,fastmoving,andotheractions.1）PlungemotionPlungecuttingtoolintoworkpiecetoobtainacertaindimension2）IndexingmotionPeriodicalmoving,rotatingofworktableortoolposttomachiningeachsurfacesofworkpiece,e.g.multi-threadscrewsturning,polygonmachining,etc.,现代数控机床原理与结构（双语）ppt课件,3）AlignmentmotionItisusedtoobtaincorrectrelativepositionsbetweencuttingtoolandworkpiece,e.g.aligningdrilltoholecenterbymovingrockerarmofthedriller.4）FastmovingandotheractionsFastmovingimprovesmachiningefficiency.Otheractionsincludedirectionchange,clamping,releasing,etc.,现代数控机床原理与结构（双语）ppt课件,2.2MachinetooldriveTorealizethosenecessarymotionsformachining,eachNCmachinetoolshouldhavethreebasicunits:

（1）Actuators,e.g.spindle,toolpost,worktable,etc.Theydirectperformmachining

（2）Drivesystem,e.g.AC/DCmotors,stepmotors,etc.Theyproducemechanicalmotionforactuators.,（3）Transmissions.Theytransfermotionandpowerfromdrivesystemtoactuators.Transmissionscanbeinmechanical,electric,hydraulicandpneumatic,现代数控机床原理与结构（双语）ppt课件,2.2.1TransmissionconnectionConnectionbetweenactuatorandpowerorbetweenactuatorsbytransmissioncomponents.,TransmissiondiagramofCA6140horizontallathe,2.2.2TransmissionchainAseriesoftransmissioncomponentsthatconsistatransmissionconnectionisknownastransmissionchain.TwoformsoftransmissionConstantratioanddirection.Variableanddirection.,Gears,wormgears-shaft,ballscrew-nut,Adjustinggears,clashgears,clutchgearshift,Transmissionchainsincludeexternalandinternalrelations:

1）ExternalrelationConnectingpowerunitandactuatorsDrivingactuatorsrunningatdesignedspeedDeterminingmachiningefficiencyandsurfaceroughnessratherthanshapeofworkpiece.,2）InternalrelationConnectingandregulatingmotionsbetweenactuators;Precisetransmissionratioisimportant.Frictionaltransmission（e.g.clutch）orinstantaneousvariableratio（chaindrive）isunacceptable;,Screwturningrequiresstringenttransmissionratiobetweenspindlerotationandtoolpostmovingtoensureprecisethreadpitch.,2.2.3TransmissiondiagramTransmissiondiagrambrieflyrepresentsrelativemotionpathsofsurfaceforming.,Symbolsfortransmissiondiagram,Transmissiondiagramofscrewturning,FromNCmachinetools,spindleandtoolpostmaybedrivenbytheirownmotors.,2.2.4Transmissionsystemdiagram:

XKA5750millingmachine,Cartesiancoordinate（Righthandrules）,Descartes（1596-1690）Frenchphilosopher,mathematician,2.3.1Standardcoordinatesystemanddirection1.ISOcoordinatesystem,2.3CoordinatesystemforNCmachinetools,2.Directionsofaxes

（1）Allaxesassumethattoolsmovewhileworktablesrest;Whenworktablemoves,itmovesalonganaxismarkedwith“;,Notes:

Worktablemotiononlybeconsideredduringmachinetooldesignstage.,

（2）Positivedirection-Themotionthatmakestoolandworkpieceapart.（3）Positiverotation-Spindlescrewsintoworkpieceinrighthandthread.,3.Axes1）Z-axisDefinition:

Paralleltotheaxisofspindle,orforthosemachinetoolsthathasnospindle（e.g.planers）,verticaltoclampingplane;Positivedirection:

toolmovesawayfromworkpiece,2）X-axisDefinition:

Usuallybehorizontal,paralleltoclampingplane,andparalleltomaincuttingdirection;,Positivedirection:

ForhorizontalZ-axis,positiveX-axispointingrightwardswhenlookingfromspindletoworkpiece.ForverticalZ-axis,positiveX-axispointingrightwardswhenlookingfromspindletocolumn.Formachinetoolsthathavenorotarycutting,X-axisparalleltothedirectionofmaincuttingforce,andthedirectionisalsodefinedaspositiveX-axis.,DefinitionsofX,Y,Z-axis,3）Y-axis-axisisverticaltobothZ,X-axisPositivedirectioncanbedefinedbyrighthandrulewithknownZ,X-axis.,DefinitionsofX,Y,Z-axis,4.AdditionalaxesForcomplexmachinetools,additionalaxesareintroducedsometimes.Secondarylinearaxes:

U,V,W-axis,more,P,Q,R-axisSecondaryrotaryaxes:

D,E,F-axis,DoublecolumnNCverticallathe,2.3.2Coordinatesystemsonmachinetools1.MachineoriginAlsoknownasabsoluteoriginorhomeposition;Aphysicalpositiononthemachinetoolsetbymanufacturer;LocatesatultimatepositivepositionsofX,Y,Z-axis.,2.ReferencepointDeterminedbystrokelimiters;Constantrelativepositiontomachineorigin（usuallyarenotsuperposed）;Preciselymeasuredbeforeleavingfactory;Formostmachiningcenters,automatictoolchangingisperformedatreferencepoint.,Coordinatesystemsonmachinetools,Verticalaxis,Horizontalaxis,2.3.3Workpiececoordinatesystem.WorkpiececoordinatesystemKnownasprogramcoordinate.Itgivesareferencepositionofeachpointofaworkpiece.Oncetheworkpiececoordinateisdetermined,positionoftheworkpieceontheworktableisdeterminedaswell.,2.WorkpieceoriginAlsoknowasprogramorigin.Itisusuallythedatumpointoftheworkpiece.UsinginstructionG92orG54G59tosetworkpieceorigin.,2.3.4ClampingoriginClampingoriginisusuallyaconstantpointonworktable.TheoffsetbetweenclampingoriginandmachineorigincanbepreciselymeasuredandstoredinCNCsystem.Forconvenient,clampingoriginsometimeslocatesonfixture.,