外文翻译---机床主轴单元

附录A英文原文MachinetoolspindleunitsA.1IntroductionMachinetoolspindlesbasicallyfulfilltwotasks:rotatethetools(drilling,millingandgrinding)orworkpiece(turning)preciselyinspacetransmittherequiredenergytothecuttingzoneformetalremovalObviouslyspindleshaveastronginfluenceonmetalremovalratesandqualityofthemachinedparts.Thispaperreviewsthecurrentstate.andpresentsresearchchallengesofspindletechnology.A.1.1.HistoricalreviewClassically,mainspindlesweredrivenbybeltsorgearsandtherotationalspeedscouldonlybevariedbychangingeitherthetransmissionratioorthenumberofdrivenpolesbyelectricalswitches.Latersimpleelectricalorhydrauliccontrollersweredevelopedandtherotationalspeedofthespindlecouldbechangedbymeansofinfinitelyadjustablerotatingtransformers(WardLeonardsystemofmotorcontrol).Theneedforincreasedproductivityledtohigherspeedmachiningrequirementswhichledtothedevelopmentofnewbearings,powerelectronicsandinvertersystems.Theprogressinthefieldofthepowerelectronics(staticfrequencyconverter)ledtothedevelopmentofcompactdriveswithlow-costmaintenanceusinghighfrequencythree-phaseasynchronousmotors.Throughtheearly1980’shighspindlespeedswereachievableonlybyusingactivemagneticbearings.Continuousdevelopmentsinbearings,lubrication,therollingelementmaterialsanddrivesystems(motorsandconverters)haveallowedtheconstructionofdirectdrivemotorspindleswhichcurrentlyfulfillawiderangeofrequirements.A.1.2.PrincipalsetupToday,theoverwhelmingmajorityofmachinetoolsareequippedwithmotorizedspindles.Unlikeexternallydrivenspindles,themotorizedspindlesdonotrequiremechanicaltransmissionelementslikegearsandcouplings.Thespindleshaveatleasttwosetsofmainlyballbearingsystems.Thebearingsystemisthecomponentwiththegreatestinfluenceonthelifetimeofaspindle.Mostcommonlythemotorisarrangedbetweenthetwobearingsystems.Duetohighratioof‘powertovolume’activecoolingisoftenrequired,whichisgenerallyimplementedthroughwaterbasedcooling.Thecoolantflowsthroughacoolingsleevearoundthestatorofthemotorandoftentheouterbearingrings.Sealsatthetoolendofthespindlepreventtheintrusionofchipsandcuttingfluid.Oftenthisisdonewithpurgeairandalabyrinthseal.AstandardizedtoolinterfacesuchasHSKandSKisplacedatthespindlesfrontend.Aclampingsystemisusedforfastautomatictoolchanges.Ideally,anunclampingunit(drawbar)whichcanalsomonitortheclampingforceisneededforreliablemachining.Ifcuttingfluidhastobetransmittedthroughthetooltothecutter,adequatechannelsandarotaryunionbecomerequiredfeaturesoftheclampingsystem.Today,nearlyeveryspindleisequippedwithsensorsformonitoringthemotortemperature(thermistorsorthermocouples)andthepositionoftheclampingsystem.Additionalsensorsformonitoringthebearings,thedriveandtheprocessstabilitycanbeattached,butarenotcommoninmanyindustrialapplications.A.1.3.StateoftheartSpindleswithhighpowerandhighspeedsaremainlydevelopedforthemachiningoflargealuminumframesintheaerospaceindustry.Spindleswithextremelyhighspeedsandlowpowerareusedinelectronicsindustryfordrillingprintedcircuitboards(PCB).A.1.4.ActualdevelopmentareasinindustryCurrentdevelopmentsinmotorspindleindustrialapplicationfocusonmotortechnology,improvingtotalcostofownership(TCO)andconditionmonitoringforpredictivemaintenanceAnothercentralissueisthedevelopmentofdrivesystemswhichneutralizetheexistingconstraintsofpowerandoutputfrequencywhilereducingtheheatingofthespindleshaft.Particularattentionwaspaidtotheincreaseofthereliablereachablerotationalspeedsinthepast.However,thefocushaschangedtowardshighertorqueatspeedsupto15,000rpm.BecauseofIncreasedrequirementsinreliability,life-cycleandpredictablemaintenancethe‘conditionmonitoring’systemsinmotorspindleshavebecomemoreimportant.Periodicand/orcontinuousobservationofthespindlestatusparametersisallowingdetectionofwear,overheatingandimminentfailures.Understandingthelifecyclecost(LCC)ofthespindleshassteadilygainedimportanceinpredictingtheirserviceperiodwithmaintenance,failureandoperationalcosts.2.FieldsofapplicationandspecificdemandsSpindlesaredevelopedandmanufacturedforawiderangeofmachinetoolapplicationswithacommongoalofmaximizingthemetalremovalratesandpartmachiningaccuracy.Theworkmaterialsrangefromeasytomachinematerialslikealuminumathighspeedswithhighpowerspindles,tonickelandtitaniumalloyswhichrequirespindleshavinghightorqueandstiffnessatlowspeeds.Cuttingworkmaterialswithabrasivecarbonorfiber-reinforcedplastics(FRP)contentneedgoodsealsatthespindlefrontend.Spindlesfordrillingprintedcircuitboardsoperateintheangularspeedrangeof100,000to300,000rpm.Theincreaseinproductivityandspeedinthisapplicationfieldoverthelastfewyearswaspossiblewiththedevelopmentofprecisionairbearings.Spindlesusedindieandmouldmachininghavetofulfilltheroughingoperations(highperformancecutting,HPC)athighfeedratesaswellasthefinishingprocesses(high-speedcutting,HSC)athighcuttingspeeds.Dependingonthestrategyandthemachineryofthemouldanddieshopeithertwodifferentmachinetoolsequippedwithtwodifferentspindlesareusedoronemachineisequippedwithaspindlechangingunit.Anotherpossibilityistouseaspindlewhichcanfulfillboth,HSCandHPCconditions,butthisstillremainsac