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西北工业大学机电学院-1-EnglishTranslationMaterial1.TransferMachineThehighestdegreeofautomationwithspecial-purpose,multifunctionmachinesisachievedbyusingtransfermachines.Transfermachineareessentiallyacombinationofindividualworkstationsarrangedintherequiredsequence,connectedbyworktransferdevices,andintegratedwithinterlockedcontrols.Workplacesareautomaticallytransferredbetweenthestations,whichareequippedwithhorizontal,vertical,orangularunitstoperformmachining,gaging,workplacerepositioning,assembling,washing,orotheroperation.Thetwomajorclassesoftransfermachinesarerotaryandin-linetypes.Animportantadvantageoftransfermachinesisthattheypermitthemaximumnumberofoperationstobeperformedsimultaneously.Thereisrelativelynolimitationonthenumberofworkplacesurfaceorplanesthatcanbemachined,sincedevicescanbeinterposedintransfermachinesatpracticallyanypointforinverting,rotating,ororientingtheworkplace,soastocompletethemachiningoperations.Workrepositioningalsominimizestheneedforangularmachiningheadsandallowsoperationstobeperformedinoptimumtime.Completeprocessingfromroughcastingorforgingtofinishedpartsisoftenpossible.Oneormorefinishedpartsareproducedonatransfermachinewitheachindexofthetransfersystemthatmovesthepartsfromstationstostations.Productionefficienciesofsuchmachinesgenerallyrangefrom50%foramachinevarietyofdifferentpartsto85%foramachineproducingonepart,inhighproduction,dependingupontheworkplaceandhowthemachineisoperated(materialhandlingmethod,maintenanceprocedures,etc.)Alltypesofmachiningoperations,suchasdrilling,tapping,reaming,boring,andmilling,areeconomicallycombinedontransfermachines.Lathe-typeoperationssuchasturningandfacingarealsobeingperformedonin-linetransfermachine,withtheworkplacebeingrotatedinselectedmachiningstations.Turningoperationsareperformedinlathe-typesegmentsinwhichtoolholdersarefedonslidesmountedontunnel-typebridgeunits.Workplacearelocatedoncentersandrotatedbychucksateachturningstation.TurningstationswithCNCareavailableforuseonin-linetransfermachine.TheCNCunitsallowthemachinecyclestobeeasilyalteredtoaccommodatechangesinworkplacedesignandcanalsobeusedforautomatictooladjustments.Maximumproductioneconomyontransferlinesisoftenachievedbyassembling西北工业大学机电学院-2-partstotheworkplacesduringtheirmovementthroughthemachine.suchitemsasbushings,seals,welchplugs,andheattubescanbeassembledandthenmachineortestedduringthetransfermachiningsequence.Automaticnuttorquingfollowingtheapplicationofpartsubassembliescanalsobecarriedout.Gundrillingorreamingontransfermachinesisanidealapplicationprovidedthatpropermachiningunitsareemployedandgoodbushingpracticesarefollowed.Contourboringandturningofsphericalseatsandothersurfacecanbedonewithtracer-controlledsingle-pointinserts,thuseliminatingtheneedforcostlyspecialformtools.In-processgagingofreamedorboredholesandautomatictoolsettingaredoneontransfermachinestomaintainclosetolerances.Lessconventionaloperationssometimesperformedontransfermachinesincludegrinding,inductionheatingofringgearsforshrink-fitpressingonflywheels,inductionhardeningofvalveseats,deeprollingtoapplycompressivepreloads,andburnishing.Transfermachineshavelongbeenusedintheautomotiveindustryforproductionrateswithaminimumofmanualparthandling.Inadditiontodecreasinglaborrequirements,suchmachinesensureconsistentlyuniform,high-qualitypartsatlowercost.Theyarenolongerconfinedjusttoroughmachiningandnowofteneliminatetheneedforsubsequentoperationssuchasgrindingandhoning.Morerecently,therehasbeenanincreasingdemandfortransfermachinestohandlelowervolumesofsimilarorevendifferentpartsinsmallersizes,withmeansforquickchangeoverbetweenproductionruns.Built-inflexibility,theabilitytorearrangeandinterchangemachineunits,andtheprovisionofidlestationsincreasesthecostofanytransfermachine,butsuchfeatureareeconomicallyfeasiblewhenproductredesignsarecommon.Manysuchmachinesarenowbeingusedinnonautomotiveapplicationsforlowerproductionrequirements.Specialfeaturenowavailabletoreducethetimerequiredforpartchangeoverincludestandardizeddimensions,modularconstruction,interchangeablefixturesmountedonmasterpalletsthatremainonthemachine,interchangeablefixturecomponents,theabilitytolockoutcertainstationsfordifferentpartsbymeansofselectorswitches,andprogrammablecontrollers.Productdesignisalsoimportant,andcommontransferandclampingsurfacesshouldbeprovidedondifferentpartswheneverpossible.2.ProgrammableLogicControllersAprogrammablelogiccontroller(PLC)isasolid-statedeviceusedtocontrolmachinemotionorprocessoperationbymeansofastoredprogram.ThePLCsendsoutputcontrolsignalsoutputandreceiveinputsignalsthroughinput/output(I/O)devices.APLCcontrolsoutputinresponsetostimuliattheinputsaccordingtothelogicprescribedbythestoredprogram.Theinputsaremadeupoflimitswitches,pushbuttons,thumbwheels,switches,pulses,analogsignal,ASCIIserialdata,andbinaryorBCDdatafromabsolutepositionencoders.Theoutputarevoltageorcurrent西北工业大学机电学院-3-leveltodriveenddevicessuchassolenoids,motorstarters,relays,lights,andsoon.Otheroutputdeviceincludeanalogdevices,digitalBCDdisplays,ASCIIcompatibledevices,servovariable-speeddri