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外文翻译--自动生产线.doc

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外文翻译--自动生产线.doc

河南科技学院机电学院1EnglishTranslationMaterial1.TransferMachineThehighestdegreeofautomationwithspecialpurpose,multifunctionmachinesisachievedbyusingtransfermachines.Transfermachineareessentiallyacombinationofindividualworkstationsarrangedintherequiredsequence,connectedbyworktransferdevices,andintegratedwithinterlockedcontrols.Workplacesareautomaticallytransferredbetweenthestations,whichareequippedwithhorizontal,vertical,orangularunitstoperformmachining,gaging,workplacerepositioning,assembling,washing,orotheroperation.Thetwomajorclassesoftransfermachinesarerotaryandinlinetypes.Animportantadvantageoftransfermachinesisthattheypermitthemaximumnumberofoperationstobeperformedsimultaneously.Thereisrelativelynolimitationonthenumberofworkplacesurfaceorplanesthatcanbemachined,sincedevicescanbeinterposedintransfermachinesatpracticallyanypointforinverting,rotating,ororientingtheworkplace,soastocompletethemachiningoperations.Workrepositioningalsominimizestheneedforangularmachiningheadsandallowsoperationstobeperformedinoptimumtime.Completeprocessingfromroughcastingorforgingtofinishedpartsisoftenpossible.Oneormorefinishedpartsareproducedonatransfermachinewitheachindexofthetransfersystemthatmovesthepartsfromstationstostations.Productionefficienciesofsuchmachinesgenerallyrangefrom50foramachinevarietyofdifferentpartsto85foramachineproducingonepart,inhighproduction,dependingupontheworkplaceandhowthemachineisoperatedmaterialhandlingmethod,maintenanceprocedures,etc.Alltypesofmachiningoperations,suchasdrilling,tapping,reaming,boring,andmilling,areeconomicallycombinedontransfermachines.Lathetypeoperationssuchasturningandfacingarealsobeingperformedoninlinetransfermachine,withtheworkplacebeingrotatedinselectedmachiningstations.Turningoperationsareperformedinlathetypesegmentsinwhichtoolholdersarefedonslidesmountedontunneltypebridgeunits.Workplacearelocatedoncentersandrotatedbychucksateachturningstation.TurningstationswithCNCareavailableforuseoninlinetransfermachine.TheCNCunitsallowthemachinecyclestobeeasilyalteredtoaccommodatechangesinworkplacedesignandcanalsobeusedforautomatictooladjustments.Maximumproductioneconomyontransferlinesisoftenachievedbyassembling河南科技学院机电学院2partstotheworkplacesduringtheirmovementthroughthemachine.suchitemsasbushings,seals,welchplugs,andheattubescanbeassembledandthenmachineortestedduringthetransfermachiningsequence.Automaticnuttorquingfollowingtheapplicationofpartsubassembliescanalsobecarriedout.Gundrillingorreamingontransfermachinesisanidealapplicationprovidedthatpropermachiningunitsareemployedandgoodbushingpracticesarefollowed.Contourboringandturningofsphericalseatsandothersurfacecanbedonewithtracercontrolledsinglepointinserts,thuseliminatingtheneedforcostlyspecialformtools.Inprocessgagingofreamedorboredholesandautomatictoolsettingaredoneontransfermachinestomaintainclosetolerances.Lessconventionaloperationssometimesperformedontransfermachinesincludegrinding,inductionheatingofringgearsforshrinkfitpressingonflywheels,inductionhardeningofvalveseats,deeprollingtoapplycompressivepreloads,andburnishing.Transfermachineshavelongbeenusedintheautomotiveindustryforproductionrateswithaminimumofmanualparthandling.Inadditiontodecreasinglaborrequirements,suchmachinesensureconsistentlyuniform,highqualitypartsatlowercost.Theyarenolongerconfinedjusttoroughmachiningandnowofteneliminatetheneedforsubsequentoperationssuchasgrindingandhoning.Morerecently,therehasbeenanincreasingdemandfortransfermachinestohandlelowervolumesofsimilarorevendifferentpartsinsmallersizes,withmeansforquickchangeoverbetweenproductionruns.Builtinflexibility,theabilitytorearrangeandinterchangemachineunits,andtheprovisionofidlestationsincreasesthecostofanytransfermachine,butsuchfeatureareeconomicallyfeasiblewhenproductredesignsarecommon.Manysuchmachinesarenowbeingusedinnonautomotiveapplicationsforlowerproductionrequirements.Specialfeaturenowavailabletoreducethetimerequiredforpartchangeoverincludestandardizeddimensions,modularconstruction,interchangeablefixturesmountedonmasterpalletsthatremainonthemachine,interchangeablefixturecomponents,theabilitytolockoutcertainstationsfordifferentpartsbymeansofselectorswitches,andprogrammablecontrollers.Productdesignisalsoimportant,andcommontransferandclampingsurfacesshouldbeprovidedondifferentpartswheneverpossible.2.ProgrammableLogicControllersAprogrammablelogiccontrollerPLCisasolidstatedeviceusedtocontrolmachinemotionorprocessoperationbymeansofastoredprogram.ThePLCsendsoutputcontrolsignalsoutputandreceiveinputsignalsthroughinput/outputI/Odevices.APLCcontrolsoutputinresponsetostimuliattheinputsaccordingtothelogicprescribedbythestoredprogram.Theinputsaremadeupoflimitswitches,pushbuttons,thumbwheels,switches,pulses,analogsignal,ASCIIserialdata,andbinaryorBCDdatafromabsolutepositionencoders.Theoutputarevoltageorcurrent河南科技学院机电学院3leveltodriveenddevicessuchassolenoids,motorstarters,relays,lights,andsoon.Otheroutputdeviceincludeanalogdevices,digitalBCDdisplays,ASCIIcompatibledevices,servovariablespeeddrives,andevencomputers.Programmablecontrollersweredevelopedcircain1968whenGeneralMotorsCorps,andotherautomobilemanufacturerswereexperimentingtoseeiftheremightbeanalternativetoscrappingalltheirhardwiredcontrolpanelofmachinetoolsandotherproductionequipmentduringamodelchangeover.Thisannualtraditionwasnecessarybecauserewritingofthepanelswasmoreexpensivethanbuyingnewones.Theautomotivecompaniesapproachedanumberofcontrolequipmentmanufacturersandaskedthemtodevelopacontrolsystemthatwouldhavealongerproductivelifewithoutmajorrewriting,butwouldstillbeunderstandabletoandrepairablebytheplantpersonnel.Thenewproductwasnamedaprogrammablecontroller.TheprocessorpartofthePLCcontainsacentralprocessingunitandmemory.ThecentralprocessingunitCPUisthetrafficdirectionoftheprocessor,thememorystoresinformation.Comingintotheprocessoraretheelectricalsignalsfromtheinputdevices,asconditionedbytheinputmoduletovoltagelevelsacceptabletoprocessorlogic.TheprocessorscansthestateofI/OandupdatesoutputsstoredinthememoryofthePLC.Forexample,theprocessormaybeprogrammedsothatifaninputconnectedtoalimitswitchistruelimitswitchclosed,thenacorrespondingoutputwiredtoanoutputmoduleistobeenergized.Thisprocessorremembersthiscommandthroughitsmemoryandcomparesoneachscantoseeifthatlimitswitchis,infact,closed.Ifitisclosed,theprocessorenergizesthesolenoidbyturningontheoutputmodule.Theoutputdevice,suchasasolenoidormotorstarter,iswiredtoanoutputmodulesterminal,anditreceivesitsshiftsignalfromtheprocessor,ineffect,theprocessorisperformingalongandcomplicatedseriesoflogicdecisions.ThePLCperformssuchdecisionssequentiallyandinaccordingwiththestoredprogram.Similarly,analogI/Oallowstheprocessortomakedecisionsbasedonthemagnitudeofasignal,ratherthanjustifitisonoroff.Forexample,theprocessormaybeprogrammedtoincreaseordecreasethesteamflowtoaboileranalogoutputbasedonacomparisonoftheactualtemperatureintheboileranaloginputThisisoftenperformedbyutilizingthebuiltinPIDproportional,integral,derivativecapabilitiesoftheprocessor.BecauseaPLCissoftwarebased,itscontrollogicfunctionscanbechangedbyreprogrammingitsmemory.Keyboardprogrammingdevicesfacilitateentryoftherevisedprogram,whichcanbedesigntocauseanexistingmachineorprocesstooperateinadifferentsequenceortodifferentlevelof,orcombinationsofstimuli.Hardwaremodificationsareneededonlyifadditional,changed,orrelocatedinput/outputdeviceareinvolved.河南科技学院机电学院43.AutomatedAssemblyAssemblyinthemanifacturingprocessconsistsofputtingtogetherallthecomponentpartsandsubassembliesofagivenproduct,fastening,performinginspectionsandfunctiontests,labeling,separatinggoodassemblyfrombad,andpackagingandorpreparingthemforfinaluse.Assemblyisuniquecomparedtothemethodsofmanufacturingsuchasmachining,grinding,andweldinginthatmostoftheseprocessesinvovleonlyafewdisciplinesandpossiblyonlyone.Mostofthesenonassemblyoperationscannotbeperformedweithouttheaidofequipmentthusthedevelopmentofautomaticmethodshasbeennecessaryratherthanoptional.Assembly,ontheotherhand,mayinvolveinonemachinemanyofthefasteningmethods,suchasriveting,welding,screwdriving,andadhesiveapplication,aswellasautomaticpartsseletion,proding,gaging,functionaltesting,labeling,andpackaging.Thestateoftheartinassemblyoperationshasnotreachedthelevelofstandardizationmuchmanualworkisstillbeingperformedinthisarea.Assemblyhastraditionallybeenoneofthehighestareasofdirectlaborcosts.Insomecases,assemblyaccountsfor50ormoreofmanufacturingcsostsandtypically20~50.However,closercooperationbetweendesignandmanufacturingengineershasresultedinreducingandinafewcaseseliminatingaltogethertheneedforassembly.Whenasssemblyisrequired,improveddesignorproductshassimplifiedautomatedsemiautomaticorautomaticassembly.ConsiderationsforAutomatedAssemblyBeforeautomatedassemblyisadopted,severalfactorsshouldbeconsiderd.Theseincludepracticalityoftheprocessforautomation,simulationforeconomicconsiderationsandjustification,managementinvolvement,andlaborrelations.DeterminingthepracticalityofautomatedassemblyrequiredcarefulevaluationofthefollowingaThenumberofpartsinassembly.bDesignofthepartswithrespecttoproducibility,assembility,automatichandling,andtestabilitymaterials,forms,dimensionaltolerances,andweights.cQualityofpartstobeassembled.Outoftoleranceordefectivepartscancauseproductionlossesandincreasecostsbecauseofstoppages.dAvailablityofqualiyied,technicallycompetentpersonaltoberesponsibleforequipmentoperation.eTotalproductionandproductionraterequipments.Productvariationsandfrequencyofdesignchanges.fJoiningmethodsrequired.gAssemblytimesandcosts.hAssemblylinesorsystemconfiguration,usingsimulation,includingmaterialhandling.

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