非圆齿轮与机械压力机运动学优化外文文献翻译中英文翻译外文翻译.docx

非圆齿轮与机械压力机运动学优化外文文献翻译中英文翻译外文翻译.docx

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非圆齿轮与机械压力机运动学优化外文文献翻译中英文翻译外文翻译

附录一:

英文文献原文

OptimizedKinematicsofMechanicalPresseswithNoncircularGears

E.Doege（l）,M.Hindersmann

ReceivedonJanuary8,1997

Abstract：

Thequalityofpartsmanufacturedusingmetalformingoperationsdependstoalargedegreeonthekinematicsofthepressram.Non-circulargearsytoobtainthosestroke-timebehavioursweaimatasanoptimumforthevariousmetalformingopewitharotational-angle-dependentspeedratiointhepressdrivemechanismofferanewwarationsintermsofmanufacturing.ThepaperexplainstheprincipleusingaprototypepresswhichwasbuiltbytheInstituteforMetalFormingandMetalFormingMachineToolsatHanoverUniversity.Itwillpresentthekinematicsaswellastheforcesandtorquesthatoccurintheprototype.Furthermore,thepaperdemonstratesusingoneexampleofdeepdrawingandoneofforgingthatthepressdrivemechanismwithnon-circulargearsmaybeusedadvantageouslyforvirtuallyallmetalformingoperations.

Keywords:

Press,Gear,Kinematics

1lntroductior

Increasingdemandsonqualityinallareasofmanufacturingengineering,insheetmetalformingaswellasinforging,gohandinhandwiththenecessitytomakeproductioneconomical.Increasingmarketorientationrequiresthatbothtechnologicalandeconomicrequirementsbemet.Theimprovementofquality,productivityandoutputbymeansofinnovativesolutionsisoneofthekeystomaintainingandextendingone'smarketposition.Intheproductionofpartsbymetalforming,weneedtodistinguishbetweentheperiodrequiredfortheactualformingprocessandthetimesneededtohandlethepart.

Withsomeformingprocesseswehavetoaddtimefornecessaryadditionalworksuchascoolingorlubricationofthedies.Thisyieldstwomethodsofoptimization,accordingtothetwoaspectsofqualityandoutput.Inordertosatisfybothaspects,thetaskistodesignthekinematicstakingintoaccounttherequirementsoftheprocessduringforming;alsotobeconsideredisthetimerequiredforchangingthepartaswellasforauxiliaryoperationsinlinewiththepriorityofashortcycletime.

2PressingMachineRequirements

Onemanufacturingcycle,whichcorrespondstoonestrokeofthepressgoesthroughthreestages:

loading,formingandremovingthepart.Insteadoftheloadingandremovalstagesweoftenfindfeedingthesheet,especiallyinsheercutting.Forthis,thepressrammusthaveaminimumheightforacertaintime.Duringtheformingperiodtheramshouldhaveaparticularvelocitycurve,whichwillbegoneintobelow.Thetransitionsbetweentheperiodsshouldtakeplaceasquicklyaspossibletoensureshortcycletime.Therequirementofashortcycletimeisforbusinessreasons,toensurelowpartscostsviahighoutput.Forthisreasonstrokenumbersofabout24/minforthedeepdrawingoflargeautomotivebodysheetsand1200/minforautomaticpunchingmachinesarestandardpractice.Increasingthenumberofstrokesinordertoreducecycletimeswithoutdesignchangestothepressingmachineresultsinincreasingstrainrates,however.Thishasacleareffectontheformingprocess,whichmakesitnecessarytoconsidertheparameterswhichdeterminetheprocessandareeffectedbyit.

Indeepdrawingoperations,thevelocityofimpactwhenstrikingthesheetshouldbeaslowaspossibletoavoidtheimpact.Ontheonehand,velocityduringformingmustbesufficientforlubrication.Ontheotherhand,wehavetoconsidertheriseintheyieldstresscorrespondingtoanincreaseinthestrainratewhichcreatesgreaterforcesandwhichmaycausefracturesatthetransitionfromthepunchradiustothesidewallofthepart.

Inforging,shortpressuredwelltimeisdesirable.AsthepressuredwelltimedropsthediesurfacetemperaturegoesdownandasaresultthethermalwearThisiscounteractedbytheenhancedmechanicalwearduetothegreaterformingforce,buttheincreaseduetothestrainrateiscompensatedbyloweryieldstressbecauseofthelowercoolingofthepart.Theoptimalshortpressuredwellcannowadaysbedeterminedquantitativelyusingthefiniteelementmethod[3].Inadditiontocostavoidanceduetoreductioninwear,shortpressuredwelltimeisalsoanimportanttechnologicalrequirementfortheprecisionforgingofnearnetshapeparts,whichhasapromisingfuture.

Therequirementsofhighpartqualityandhighoutputwillonlybemetbyamachinetechnologywhichtakesintoaccountthedemandsofthemetalformingprocessinequalmeasuretothegoalofdecreasingworkproductioncosts.Previouspressdesignshavenotsimultaneouslymetthesetechnologicalandeconomicalrequirementstoasufficientextent,ortheyareverycostlytodesignand

manufacture,suchaspresseswithlinkdrives[6].Thismakesitnecessarytolookforinnovativesolutionsforthedesignofthepress.Itsdesignshouldbelargelystandardizedandmodularizedinordertoreducecosts[6].

Fig1.Prototypepress

3PressDrivewithNoncircularGears

3.1Principle

Theuseofnon-circulargearsinthedriveofmechanicalcrankpressesoffersanewwayofmeetingthetechnologicalandeconomicdemandsonthekinematicsofthepressram.Apairofnon-circulargearswithaconstantcenterdistanceisthuspoweredbytheelectricmotor,orbytheflywheel,anddrivesthecrankmechanismitself.Theuniformdrivespeedistransmittedcyclicallyand

non-uniformlytotheeccentricshaftbythepairofnoncirculargears.Ifthenon-circulargearwheelsaresuitablydesigned,thenon-uniformdriveofthedrivengearleadstothedesiredstroke-timebehaviouroftheram.InvestigationsattheInstituteforMetalFormingandMetalFormingMachineTools（IFUM）ofHanoverUniversityhaveshownthatinthissimplemanneralltherelevantuninterruptedmotionsoftheramcanbeachievedforvariousformingprocesses[2].

Apartfrom,theadvantagesofthenewdrive,whichresultfromthekinematicsandtheshortenedcycletime,thedriveconceptisdistinguishedbythefollowingfavourablepropertties.Becauseitisamechanicalpress,highreliabilityandlowmaintenancemaybeexpected.Incomparisiontolinkagepressesthenumberofpartsandbearingsisclearlyreduced.Aboveall,abasicpresstypecanbevariedwithoutfurtherdesignchangesbyinstallingdifferentpairsofgears,designedaccordingtothedemands

ofthecustomer.Unlikelinkdrives,bearinglocationsandinstallationsdonotchangewithinoneload

classasaresultofdifferentkinematics.ThustheabovementionedrequirementofmodularizationandstandardizationistakenintoaccountReductionsintimeandcostsarepossibleforthedesignandpressmanufacture.

3.2Prototype

AttheInstituteforMetalFormingandMetalFormingMachineTools（IFUM）aC-framepresshasbeenremodeledandapairofnon-circulargearswasinstalled.Thepreviousbackgearswerereplacedbyaplanetarygearsetforthispurpose.Theworkcarriedoutshowsthatremodelingofexistingpressesforthenewdriveispossible.Thestateofthepressattheendoftheremodellingisshowninfiqure1.Thepressisdesignedforanominalramforceof1,000kNand200kNofthediecushion.Thecenterdistanceofthenon-circulargearsis600mm.Thepairofnon-circulargearshasanaveragetransmissionratioof1.Eachgearwheelhas59gearteeth,straight-toothed,module10mm（fiaure2）.Thefacewidthis150mm.Thegearshaveinvolutegearteeth.Weassumeanon-circularbasecurveforthedesignoftheflankgeometry.Asaresultthetoothgeometryofanon-circulargearvariesalongthecircumference.Inspiteofthis,itcanbederivedfromthewell-knowntrapeziumrack,however[4,51.Analgorithmforthecomputation,whichtakestheaddendumanddedendumintoaccountexactly,hasbeendeveloped.

Fig.2Viewofthegearsfromtherear

Thepressisdesignedfordeepdrawingofflatpartsinsinglestrokeoperationmode.Themaximumramstrokeis180mm,thenumberofstrokes32/min.Atastrokeof140mmtheramvelocityalmostremainsconstant71mmlsfrom60mmbeforelowerdeadcenteruntillowerdeadcenter,seefiqure3.Thusthevelocitycorrespondstotheworkingvelocityofhydraulicpresses.Thevelocityofincidenceofacrankmechanismwiththesamenumberofstrokeswouldbe220mmls,incomparison.Inordertokeepthesameaveragevelocitywithacrankpress,thenumberofstrokeswouldhavetobehalved.Theshort

cycletimeoftheremodelledmachineresultsfromthefastupwardmotion.Becausethepressisruninsinglestrokeoperationmode,noparticularrequirementsweremadeconcerninghandlingtimeduringdesign.

Thedrivemechanismoftheprototypewithnon-circulargearshasinadditionafavourableeffectontheramforcesandthedrivingtorques（ficlure4）.Foracrankpressthenominalforceisnormallyavailableat30"rotationofthecrankshaftbeforethelowerdeadcenter.Thiscorrespondstoasectionundernominalforceofonly75%relativetothestroke.Toreachthenominalforceof1,000kN,thedrivehastosupplyatorqueof45kNmatthecrankshaft.Theprototypeonlyrequires30kNmonaccountoftheadditionaltransmissionofthenon-circulargears.Theyaretransmittedtoacyclic.non-uniformcrankshafttorque,resultinginanominalforcerangefrom60"tothelowerdeadcenter.Thiscorrespondsto27.5%ofthestroke.Wealwaysfindsimilarconditionsifthepairofnon-circulargearsissteppeddownintheoperatingrangeofthepress.Thiswillalmostalwaysbethecasewithsheetmetalformingandstamping.Itisthuspossibletodesignsomemachinepartsinaweakerformandtosavecoststhisway.

4FurtherDesignExamples

Usingtheexamplesoftwostroke-timebehavioursthedesignisillustratedinthefollowing.A