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外文翻译---五轴磨床加工工具运动链的设计和分析 英文版.pdf

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外文翻译---五轴磨床加工工具运动链的设计和分析 英文版.pdf

InternationalJournalofMachineToolsManufacture422002505–520FiveaxismillingmachinetoolkinematicchaindesignandanalysisE.L.J.BohezDepartmentofDesignandManufacturingEngineering,AsianInstituteofTechnology,P.O.Box4,KlongLuang,12120Pathumthani,ThailandReceived23May2000receivedinrevisedform12September2001accepted13September2001AbstractFiveaxisCNCmachiningcentershavebecomequitecommontoday.ThekinematicsofmostofthemachinesarebasedonarectangularCartesiancoordinatesystem.Thispaperclassifiesthepossibleconceptualdesignsandactualexistingimplementationsbasedonthetheoreticallypossiblecombinationsofthedegreesoffreedom.Someusefulquantitativeparameters,suchastheworkspaceutilizationfactor,machinetoolspaceefficiency,orientationspaceindexandorientationangleindexaredefined.Theadvantagesanddisadvantagesofeachconceptareanalyzed.Criteriaforselectionanddesignofamachineconfigurationaregiven.NewconceptsbasedontheStewartplatformhavebeenintroducedrecentlyinindustryandarealsobrieflydiscussed.2002ElsevierScienceLtd.Allrightsreserved.KeywordsFiveaxisMachinetoolKinematicchainWorkspaceCNCRotaryaxis1.IntroductionThemaindesignspecificationsofamachinetoolcanbededucedfromthefollowingprinciplesL50539Thekinematicsshouldprovidesufficientflexibilityinorientationandpositionoftoolandpart.L50539Orientationandpositioningwiththehighestpossiblespeed.L50539Orientationandpositioningwiththehighestpossibleaccuracy.L50539Fastchangeoftoolandworkpiece.L50539Savefortheenvironment.L50539Highestpossiblematerialremovalrate.Thenumberofaxesofamachinetoolnormallyreferstothenumberofdegreesoffreedomorthenumberofindependentcontrollablemotionsonthemachineslides.TheISOaxesnomenclaturerecommendstheuseofarighthandedcoordinatesystem,withthetoolaxiscorrespondingtotheZaxis.AthreeaxismillingmachinehasthreelinearslidesX,YandZwhichcanbepositionedeverywherewithinthetravellimitofeachslide.Thetoolaxisdirectionstaysfixedduringmachining.ThislimitsTel.6625245687fax6625245697.Emailaddressbohezait.ac.thE.L.J.Bohez.08906955/02/seefrontmatter2002ElsevierScienceLtd.Allrightsreserved.PIIS0890695501001341theflexibilityofthetoolorientationrelativetotheworkpieceandresultsinanumberofdifferentsetups.Toincreasetheflexibilityinpossibletoolworkpieceorientations,withoutneedofresetup,moredegreesoffreedommustbeadded.Foraconventionalthreelinearaxesmachinethiscanbeachievedbyprovidingrotationalslides.Fig.1givesanexampleofafiveaxismillingmachine.Fig.1.Fiveaxismachinetool.506E.L.J.Bohez/InternationalJournalofMachineToolsManufacture422002505–5202.KinematicchaindiagramToanalyzethemachineitisveryusefultomakeakinematicdiagramofthemachine.Fromthiskinematicchaindiagramtwogroupsofaxescanimmediatelybedistinguishedtheworkpiececarryingaxesandthetoolcarryingaxes.Fig.2givesthekinematicdiagramofthefiveaxismachineinFig.1.Ascanbeseentheworkpieceiscarriedbyfouraxesandthetoolonlybyoneaxis.Thefiveaxismachineissimilartotwocooperatingrobots,onerobotcarryingtheworkpieceandonerobotcarryingthetool.Fivedegreesoffreedomaretheminimumrequiredtoobtainmaximumflexibilityintoolworkpieceorientation,thismeansthatthetoolandworkpiececanbeorientedrelativetoeachotherunderanyangle.Theminimumrequirednumberofaxescanalsobeunderstoodfromarigidbodykinematicspointofview.Toorienttworigidbodiesinspacerelativetoeachother6degreesoffreedomareneededforeachbodytoolandworkpieceor12degrees.Howeveranycommontranslationandrotationwhichdoesnotchangetherelativeorientationispermittedreducingthenumberofdegreesby6.Thedistancebetweenthebodiesisprescribedbythetoolpathandallowseliminationofanadditionaldegreeoffreedom,resultinginaminimumrequirementof5degrees.3.LiteraturereviewOneoftheearliest1970andstillveryusefulintroductionstofiveaxismillingwasgivenbyBaughman1clearlystatingtheapplications.TheAPTlanguagewasthentheonlytooltoprogramfiveaxiscontouringapplications.TheproblemsinpostprocessingwerealsoFig.2.Kinematicchaindiagram.clearlystatedbySim2inthoseearlierdaysofnumericalcontrolandmostissuesarestillvalid.BoydinRef.3wasalsooneoftheearlyintroductions.Beziersbook4isalsostillaveryusefulintroduction.Held5givesaverybriefbutenlighteningdefinitionofmultiaxismachininginhisbookonpocketmilling.ArecentpaperapplicabletotheproblemoffiveaxismachineworkspacecomputationisthemultiplesweepingusingtheDenawitHartenbergrepresentationmethoddevelopedbyAbdelMalekandOthman6.ManytypesanddesignconceptsofmachinetoolswhichcanbeappliedtofiveaxismachinesarediscussedinRef.7butnotspecificallyforthefiveaxismachine.ThenumberofsetupsandtheoptimalorientationofthepartonthemachinetableisdiscussedinRef.8.AreviewaboutthestateoftheartandnewrequirementsfortoolpathgenerationisgivenbyB.K.Choietal.9.GraphicsimulationoftheinteractionofthetoolandworkpieceisalsoaveryactiveareaofresearchandagoodintroductioncanbefoundinRef.10.4.ClassificationoffiveaxismachineskinematicstructureStartingfromRotaryRandTranslatoryTaxesfourmaingroupscanbedistinguishedithreeTaxesandtwoRaxesiitwoTaxesandthreeRaxesiiioneTaxisandfourRaxesandivfiveRaxes.Nearlyallexistingfiveaxismachinetoolsareingroupi.Alsoanumberofweldingrobots,filamentwindingmachinesandlasermachiningcentersfallinthisgroup.Onlylimitedinstancesoffiveaxismachinetoolsingroupiiexistforthemachiningofshippropellers.Groupsiiiandivareusedinthedesignofrobotsusuallywithmoredegreesoffreedomadded.Thefiveaxescanbedistributedbetweentheworkpieceortoolinseveralcombinations.Afirstclassificationcanbemadebasedonthenumberofworkpieceandtoolcarryingaxesandthesequenceofeachaxisinthekinematicchain.Anotherclassificationcanbebasedonwheretherotaryaxesarelocated,ontheworkpiecesideortoolside.ThefivedegreesoffreedominaCartesiancoordinatesbasedmachinearethreetranslatorymovementsX,Y,ZingeneralrepresentedasTTTandtworotationalmovementsAB,ACorBCingeneralrepresentedasRR.CombinationsofthreerotaryaxesRRRandtwolinearaxesTTarerare.Ifanaxisisbearingtheworkpieceitisthehabitofnotingitwithanadditionalaccent.ThefiveaxismachineinFig.1canbecharacterizedbyXH11032YH11032AH11032BH11032Z.TheXYABaxescarrytheworkpieceandtheZaxiscarriesthetool.Fig.3showsamachineofthetypeXYZAH11032BH11032,thethreelinearaxescarrythetoolandthetworotaryaxescarrytheworkpiece.507E.L.J.Bohez/InternationalJournalofMachineToolsManufacture422002505–520Fig.3.XYZAH11032BH11032machinery.4.1.ClassificationbasedonthesequenceofworkpieceandtoolcarryingaxesTheoreticallythenumberofpossibleconfigurationsisquitelargeiftheorderoftheaxesinthetwokinematicchainsofthetoolandworkpiececarryingaxesiscountedasadifferentconfiguration.Alsothecombinationswithonlytwolinearaxesandthreerotaryaxesareincluded.OnetoolcarryingaxisandfourworkpiececarryingaxescanbecombinedinafiveaxismachineasfollowsforeachpossibletoolcarryingaxisX,Y,Z,A,B,Ctheotherfourworkpiececarryingaxescanbeselectedfromthefiveremainingaxes.Sothenumberofcombinationsoffouraxesoutoffivewithconsideringdifferentpermutationasanotherconfigurationis54120foreachpossibletoolaxisselection1outof6or6possibilities.Sotheoreticallythereare6120720possiblefiveaxismachineswithonetoolcarryingaxis.Thesameanalysiscanbedoneforallothercombinations.Withtthenumberoftoolcarryingaxesandwthenumberofworkpiececarryingaxeswt5thetotalnumberofcombinationsisasfollows.NcombH208736tH20874tH208736−twH20874wtH113493,tw51NcombH208736wH20874wH208736−wtH20874ttH110223,tw52Thevalueofthisequationisalwaysequalto6or720whenwt5.Someofthese720combinationswillbecontainingonlytwolinearaxis.Ifonlyfiveaxismachineswiththreelinearaxesareconsidered,only35360combinationsarestillpossible.ThesetGtofcombinationsischaracterizedbyafixedvalueoft.ThissetisidenticaltothesetGH11032wcharacterizedbyafixedvalueofw,w5H11002t.UsingabovedefinitionsfollowingsubgroupsoffiveaxismachinesexistiGroupG0/GH110325iiGroupG1/GH110324iiiGroupG2/GH110323ivGroupG3/GH110322vGroupG4/GH110321viGroupG5/GH110320.4.1.1.G5/G0H11032machineAllaxescarrythetoolandtheworkpieceisfixedonafixedtable.Fig.4showsamachinewithallthefiveaxescarryingthetool.ThekinematicchainisXBYAZTRTRT.Thismachinewasoneoftheearliestmodelsoffiveaxismachinestohandleveryheavyworkpieces.Astherearemanylinksinthetoolcarryingkinematicchain,therecanbeaconsiderableerrorduetoelasticdeformationsandbacklashintheslides.4.1.2.G0/G5H11032machineAllaxescarrytheworkpieceandthetoolisfixedinspace.ThisconstructionisbestusedforverysmallworkpiecesseeSection6.3.Fig.4.XBYAZmachine.508E.L.J.Bohez/InternationalJournalofMachineToolsManufacture422002505–5204.1.3.G4/G1H11032machineFouraxescarrythetoolandoneaxiscarriestheworkpiece.Therearebasicallytwopossibilities,theworkpiececarryingaxiscanbeRH11032orTH11032.4.1.4.G1/G4H11032machineOneaxiscarriesthetoolandtheotherfouraxescarrytheworkpiece.Therearebasicallytwopossibilities,thesingleaxiskinematicchaincanbeRorT.Fig.1isanexampleofsuchamachine,withthesingletoolcarryingaxisT.4.1.5.G3/G2H11032machineThreeaxescarrythetoolandtwoaxescarrytheworkpiece.Therearebasicallythreepossibilities,theworkpiececarryingaxescanbebothlinearTH11032TH11032bothrotationalRH11032RH11032ormixedTH11032RH11032.Fig.5givesanexampleofamachinewiththetoolcarriedbytworotaryaxesandonelinearaxis.Thismachineallowsprocessingoflargeworkpiecesbuttheconstructionofthetoolsideiscomplicated.ThemostcommonconfigurationistheworkpiececarriedbythetworotaryaxessuchastheonegiveninFigs.3,6and8.4.1.6.G2/G3H11032machineTwoaxescarrythetoolandthreeaxescarrytheworkpiece.Therearebasicallythreepossibilities,thetoolcarryingaxiscanbebothlinearTTbothrotationalRRormixedTR.Fig.7showsthemixedconstruction.Fig.8showstwolinearaxescarryingthetool.4.2.ClassificationbasedonthelocationofrotaryaxesThemachinescanbeclassifieddependingontheplacewheretherotationaxesareimplemented.Fig.5.XH11032ZH11032CAYmachine.Fig.6.BH11032CH11032ZYXmachine.Fig.7.ZH11032XH11032CH11032BYmachine.

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