外文翻译--生产自动化.doc

《外文翻译--生产自动化.doc》由会员分享，可在线阅读，更多相关《外文翻译--生产自动化.doc（15页珍藏版）》请在装配图网上搜索。

1、共7页第1页ProductionAutomationIntroductiontoproductionAutomationAutomationisawidelyusedterminmanufacturing.Inthiscontext,automationcanbedefinedastechnologyconcernedwiththeapplicationofmechanical,electronic,andcomputer-basedsystemstooperateandcontrolproduction.Examplesofthistechnologyinclude:Automaticmac

2、hinetoolstoprocessparts.AutomatedtransferlinesandsimilarsequentialproductionsystemsAutomaticassemblymachinesIndustrialrobotsAutomaticmaterialhandingandstoragesystemsAutomatedinspectionsystemsforqualitycontrol.Feedbackcontrolandcomputerprocesscontrol.Computersystemsthatautomateproceduresforplanning,d

3、atacollection,anddecisionmakingtosupportmanufacturingactivities.Automatedproductionsystemscanbeclassifiedintotwobasiccategories:fixedautomationandprogrammableautomation.FixedAutomationFixedautomationiswhatHarderwasreferringtowhenhecoinedthewordautomation.Fixedautomationreferstoproductionsystemsinwhi

4、chthesequenceofprocessingorassemblyoperationsisfixedbytheequipmentconfigurationandcannotbereadilychangedwithoutalteringtheequipment.Althougheachoperationinthesequenceisusuallysimple,theintegrationandcomplex.Typicalfeaturesoffixedautomationinclude1.highinitialinvestmentforcustom-engineeredequipment,2

5、.highproductionrates,3.applicationtoproductsinwhichhighquantitiesaretobeproduced,and4.relativeinflexibilityinaccommodatingproductchanges.Fixedautomationiseconomicallyjustifiableforproductswithhighdemandrates.Thehighinitialinvestmentintheequipmentcanbedividedoveralargenumberofunits,perhapsmillions,th

6、usmakingtheunitcostlowcomparedwithalternativemethodsofproduction.Examplesoffixedautomationincludetransferlinesformachining,dialindexingmachines,andautomatedassemblymachines.Muchofthe共7页第2页technologyinfixedautomationwasdevelopedintheautomobileindustry；thetransferline(datingtoabout1920)isanexample.Pro

7、grammableAutomationForprogrammableautomation,theequipmentisdesignedinsuchawaythatthesequenceofproductionoperationsiscontrolledbyaprogram,i.e.,asetofcodedinstructionsthatcanbereadandinterpretedbythesystem.Thustheoperationsequencecanbereadilychangedtopermitdifferentproductconfigurationstobeproducedont

8、hesameequipment.Someofthefeaturesthatcharacterizeprogrammableautomationinclude1.highinvestmentingeneral-purposeprogrammableequipment,2.lowerproductionratesthanfixedautomation,3.flexibilitytodealwithchangesinproductconfiguration,and4.suitedtolowand/ormediumproductionofsimilarproductsorparts(e.g.partf

9、amilies).Examplesofprogrammableautomationincludenumericallycontrolledmachinetools,industrialrobots,andprogrammablelogiccontrollers.Programmableproductionsystemsareoftenusedtoproducepartsorproductsinbatches.Theyareespeciallyappropriatewhenrepeatordersforbatchesofthesameproductareexpected.Toproduceeac

10、hbatchofanewproduct,thesystemmustbeprogrammedwiththesetofmachineinstructionsthatcorrespondtothatproduct.Thephysicalsetupoftheequipmentmustalsobechanged；specialfixturesmustbeattachedtothemachine,andtheappropriatetoolsmustbeloaded.Thischangeoverprocedurecanbetime-consuming.Asaresult,theusualproduction

11、cycleforagivenbatchincludes1.aperiodduringwhichthesetupandreprogrammingisaccomplishedand2.aperiodinwhichthebatchisprocessed.Thesetup-reprogrammingperiodconstitutesnonproductivetimeoftheautomatedsystem.Theeconomicsofprogrammableautomationrequirethatasthesetup-reprogrammingtimeincrease,theproductionba

12、tchsizemustbemadelargersoastospreadthecostoflostproductiontimeoveralargernumberofunits.Conversely,ifsetupandreprogrammingtimecanbereducedtozero,thebatchsizecanbereducedtoone.Thisisthetheoreticalbasisforflexibleautomation,anextensionofprogrammableautomation.Aflexibleautomatedsystemisonethatiscapableo

13、fproducingavarietyofproducts(orparts)withminimallosttimeforchangeoversfromoneproducttothenext.Thetimetoreprogramthesystemandalterthephysicalsetupisminimalandresultsinvirtuallynolostproductiontime.Consequently,thesystemiscapableofproducingvariouscombinationsandschedules共7页第3页ofproductsinacontinuousfl

14、ow,ratherthanbatchproductionwithinterruptionsbetweenbatches.Thefeaturesofflexibleautomationare1.highinvestmentforacustom-engineeredsystem,2.continuousproductionofmixturesofproducts,3.abilitytochangeproductmixtoaccommodatechangesindemandratesforthedifferentproductsmade,4.mediumproductionrates,and5.fl

15、exibilitytodealwithproductdesignvariations.Flexibleautomatedproductionsystemsoperateinpracticebyoneormoreofthefollowingapproaches:1.usingpartfamilyconcepts,bywhichthepartsmadeonthesystemarelimitedinvariety；2.reprogrammingthesysteminadvanceand/oroff-line,sothatreprogrammingdoesnotinterruptproduction；

16、3.downloadingexistingprogramstothesystemtoproducepreviouslymadepartsforwhichprogramarealreadyprepared；4.usingquick-changefixturessothatphysicalsetuptimeisminimized；5.usingafamilyoffixturesthathavebeendesignedforalimitednumberofpartstyles；and6.equippingthesystemwithalargenumberofquick-changetoolsthat

17、includethevarietyofprocessingoperationsneededtoproducethepartfamily.Fortheseapproachestobesuccessful,thevariationinthepartstylesproducedonaflexibleautomatedproductionsystemisusuallymorelimitedthatabatch-typeprogrammableautomationsystem.Examplesofflexibleautomationaretheflexiblemanufacturingsystemsfo

18、rperformingmachiningoperationsthatdatebacktolate1960s.NumericalControlNumericalcontrol(oftenabbreviatedNC)canbedefinedasaformofprogrammableautomationinwhichtheprocessiscontrolledbynumbers,letters,andsymbols.InNC,thenumbersformaprogramofinstructionsdesignedforaparticularworkpartorjob.Whenthejobchange

19、s,theprogramofinstructionsischanged.ThiscapabilitytochangetheprogramforeachnewjobiswhatgivesNCitsflexibility.Itismucheasiertowritenewprogramsthantomakemajorchangesintheproductionequipment.NCequipmentisusedinallareasofmetalpartsfabricationandcomprisesroughly15%ofthemodernmachinetoolsinindustrytoday.S

20、incenumericallycontrolledmachinesareconsiderablymoreexpensivethantheirconventionalcounterparts,theassetvalueofindustrialNCmachinetoolsisproportionallymuchlargerthantheirnumbers.Equipmentutilizingnumericalcontrolhasbeendesigned共7页第4页toperformsuchdiverseoperationsasdrilling,milling,turning,grinding,sh

21、eetmetalpressworkingspotwelding,arewelding,riveting,assembly,drafting,inspection,andpartshandling.Andthisisbynomeansacompletelist.Numericalcontrolshouldbeconsideredasapossiblemodeofcontrollingtheoperationforanyproductionsituationpossessingthefollowingcharacteristics:1.Similarworkpartsintermsofrawmat

22、erial(e.g.,metalstockformachining).2.Theworkpartsareproducedinvarioussizesandgeometries.3.Theworkpartsareproducedinbatchesofsmalltomedium-sizedquantities.4.Asequenceofsimilarprocessingstepsisrequiredtocompletetheoperationoneachworkpiece.Manymachiningjobsmeettheseconditions.Themachinedworkpartsaremet

23、al,theyarespecifiedinmanydifferentsizesandshapes,andmostmachinedpartsproducedinindustrytodayaremadeinsmalltomedium-sizelotsizes.Toproduceeachpart,asequenceofdrillingoperationsmayberequired,oraseriesofturningormillingoperations.ThesuitabilityofNCforthesekindsofjobsisthereasonforthetremendousgrowthofn

24、umericalcontrolinthemetalworkingindustryoverthelast25years.BasicComponentsofanNCSystemAnoperationalnumericalcontrolsystemconsistsofthefollowingthreebasiccomponents:1.Programofinstructions.2.Controllerunit,alsocalledmachinecontrolunit(MCU).3.Machinetoolorothercontrolledprocess.TransferMachinesThehigh

25、estdegreeofautomationobtainablewithspecial-purpose,multifunctionmachinesisachievedbyusingtransfermachines.Transfermachinesareessentiallyacombinationofindividualworkstationsarrangedintherequiredsequence,connectedbyworktransferdevices,andintegratedwithinterlockedcontrols.Workpiecesareautomaticallytransferredbetweenthestations,whichareequippedwithhorizontal,vertical,orangularunitstoperformmachining,gagging,workpiecerepositioning,assembling,washing,orotheroperations.Thetwomajorclassesoftransfermachinesarerotaryandin-linetypes.