柔性制造中英文翻译外文文献翻译Word文档下载推荐.docx
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柔性制造中英文翻译外文文献翻译Word文档下载推荐.docx
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*Processequipmente.g.,machinetools,assemblystations,androbots
*Materialhandlingequipmente.g.,robots,conveyors,andAGVs(automatedguidedvehicles)
*Acommunicationsystem
*Acomputercontrolsystem
Flexiblemanufacturingrepresentsamajorsteptowardthegoaloffullyintegratedmanufacturing.Itinvolvesintegrationofautomatedproductionprocesses.Inflexiblemanufacturin,theautomatedmanufacturingmachineandtheautomatedmaterialshandlingsystemshareinstantaneouscommunicationviaacomputernetwork.Thisisintegrationonasmallscale.
Flexiblemanufacturingtakesamajorsteptowardthegoaloffullyintegratedmanufacturingbyintegratingseveralautomatedmanufacturingconcepts:
*Computernumericalcontrol(CNC)ofindividualmachinetools
*Distributednumericalcontrol(DNC)ofmanufacturingsystems
*Automatedmaterialshandlingsystems
*Grouptechnology(familiesofparts)
Whentheseautomatedprocesses,machines,andconceptsarebroughttogetherinoneintegratedsystem,anFMSistheresult.HumansandcomputersplaymajorrolesinanFMS.Theamountofhumanlaborismuchlessthanwithamanuallyoperatedmanufacturingsystem,ofcourse.However,humansstillplayavitalroleintheoperationofanFMS.Humantasksincludethefollowing:
*Equipmenttroubleshooting,maintenance,andrepair
*Toolchangingandsetup
*Loadingandunloadingthesystem
*Datainput
*Changingofpartsprograms
*Developmentofprograms
Flexiblemanufacturingsystemequipment,likeallmanufacturingequipment,mustbemonitoredforbugs,malfunctions,andbreakdowns.Whenaproblemisdiscovered,ahumantroubleshootermustidentifyitssourceandprescribecorrectivemeasures.Humansalsoundertaketheprescribedmeasurestorepairthemalfunctioningequipment.Evenwhenallsystemsareproperlyfunctioning,periodicmaintenanceisnecessary.
Humanoperatorsalsosetupmachines,changetools,andreconfiguresystemsasnecessary.ThetoolhandlingcapabilityofanFMSdecreases,butdoesnoteliminateinvolvementintoolchangingandsetup.ThesameistrueofloadingandunloadingtheFMS.Oncerawmaterialhasbeenloadedontotheautomatedmaterialshandlingsystem,itismovedthroughthesystemintheprescribedmanner.However,theoriginalloadingontothematerialshandlingsystemisstillusuallydonebyhumanoperators,asistheunloadingoffinishedproducts.
Humansarealsoneededforinteractionwiththecomputer.HumansdeveloppartprogramsthatcontroltheFMSviacomputers.TheyalsochangetheprogramsasnecessarywhenreconfiguringtheFMStoproduceanothertypeofpartorparts.Humansplaylesslabor-intensiverolesinanFMS,buttherolesarestillcritical.
ControlatalllevelsinanFMSisprovidedbycomputers.IndividualmachinetoolswithinanFMSarecontrolledbyCNC.TheoverallsystemiscontrolledbyDNC.Theautomatedmaterialshandlingsystemiscomputercontrolled,asareotherfunctionsincludingdatacollection,systemmonitoring,toolcontrol,andtrafficcontrol.Human/computerinteractionisthekeytotheflexibilityofanFMS.
1HistoricalDevelopmentofFlexibleManufacturing
Flexiblemanufacturingwasborninthemid-1960swhentheBritishfirmMolins,Ltd.DevelopeditsSystem24.System24wasarealFMS.However,itwasdoomedfromtheoutsetbecauseautomation,integration,andcomputercontroltechnologyhadnotyetbeendevelopedtothepointwheretheycouldproperlysupportthesystem.ThefirstFMSwasadevelopmentthatwasaheadofitstime.Assuch,itwaseventuallydiscardedasunworkable.
Flexiblemanufacturingremainedanacademicconceptthroughtheremainderofthe1960sand1970s.However,withtheemergenceofsophisticatedcomputercontroltechnologyinthelate1970sandearly1980s,flexiblemanufacturingbecameaviableconcept.ThefirstmajorusersofflexiblemanufacturingintheUnitedStatesweremanufacturersofautomobiles,trucks,andtractors.
2RationaleforFlexibleManufacturing
Inmanufacturingtherehavealwaysbeentradeoffsbetweenproductionratesandflexibility.Atoneendofthespectrumaretransferlinescapableofhighproductionrates,butlowflexibility.AttheotherendofthespectrumareindependentCNCmachinesthatoffermaximumflexibility,butarecapableonlyoflowproductionrates.Flexiblemanufacturingfallsinthemiddleofcontinuum.Therehasalwaysbeenaneedinmanufacturingforasystemthatcouldproducehighervolumeandproductionrunsthancouldindependentmachines,whilestillmaintainingflexibility.
Transferlinesarecapableofproducinglargevolumesofpartsathighproductionrates.Thelinetakesagreatdealofsetup,butcanturnoutidenticalinapartcancausetheentirelinetobeshutdownandreconfigured.Thisisacriticalweaknessbecauseitmeansthattransferlinescannotproducedifferentparts,evenpartsfromwithinthesamefamily,withoutcostlyandtime-consumingshutdownandreconfiguration.
Traditionally,CNCmachineshavebeenusedtoproducesmallvolumesofpartsthatdifferslightlyindesign.Suchmachinesareidealforthispurposebecausetheycanbequicklyreprogrammedtoaccommodateminororevenmajordesignchanges.However,asindependentmachinestheycannotproducepartsinlargevolumesorathighproductionrates.
AnFMScanhandlehighervolumesandproductionratesthanindependentCNCmachines.Theycannotquitematchsuchmachinesforflexibility,buttheycomeclose.Whatisparticularlysignificantaboutthemiddlegroundcapabilitiesofflexiblemanufacturingisthatmostmanufacturingsituationsrequiremediumproductionratestoproducemediumvolumeswithenoughflexibilitytoquicklyreconfiguretoproduceanotherpartorproduct.Flexiblemanufacturingfillsthislong-standingvoidinmanufacturing.
Flexiblemanufacturing,withitsgroundcapabilities,offersanumberofadvantagesformanufacturers:
*Flexibilitywithinafamilyofparts
*Randomfeedingofparts
*Simultaneousproductionofdifferentparts
*Decreasedsetuptimeandleadtime
*Moreefficientmachineusage
*Decreaseddirectandindirectlaborcosts
*Abilitytohandledifferentmaterials
*Abilitytocontinuesomeproductionifonemachinebreaksdown
3FlexibleManufacturingSystemComponents
AnFMShasfourmajorcomponents:
*Machinetools
*Controlsystem
*Materialshandlingsystem
*Humanoperators
(1)MachineTools
Aflexiblemanufacturingsystemusesthesametypesofmachinetoolsasanyothermanufacturingsystem,beitautomatedormanuallyoperated.Theseincludelathes,mills,drills,saws,andsoon.ThetypeofmachinetoolsactuallyincludedinanFMSdependsonthesettinginwhichthemachinewillbeused.SomeFMSaredesignedtomeetaspecific,well-definedneed.Inthesecasesthemachinetoolsincludedinthesystemwillbeonlythosenecessaryfortheplannedoperations.Suchasystemwouldbeknownasadedicatedsystem.
Inajob-shopsetting,oranyothersettinginwhichtheactualapplicationisnotknownaheadoftimeormustnecessarilyincludeawiderangeofpossibilities,machinescapableofperformingatleastthestandardmanufacturingoperationswouldbeinclude.Suchsystemsareknownasgeneralpurposesystems.
(2)ControlSystem
ThecontrolsystemforanFMSservesanumberofdifferentcontrolfunctionsforsystem:
*Storageanddistributionofpartsprograms
*Workflowcontrolandmonitoring
*Productioncontrol
*System/toolcontrol/monitoring
ThecontrolareawiththecomputerrunningtheFMScontrolsystemisthecenterfromwhichallactivitiesintheFMSarecontrolledandmonitored.TheFMScontrolsoftwareisrathercomplicatedandsophisticatedsinceithastocarryoutmanydifferenttaskssimultaneously.Despitetheconsiderableresearchthathasbeencarriedoutinthisarea,thereisnogeneralanswertodesigningthefunctionsandarchitectureofFMSsoftware.
TheschedulerfunctioninvolvesplanninghowtoproducethecurrentvolumeofordersintheFMS,consideringthecurrentstatusofmachinetools,work-in-process,tooling,andsoon.Theschedulingcanbedoneautomaticallyorcanbeassistedbyanoperator.MostFMScontrolsystemscombineautomaticandmanualscheduling;
thesystemgeneratesaninitialschedulethatcanbechangedmanuallybytheoperator.Thedispatcherfunctioninvolvescarryingoutthescheduleandcoordinatingtheactivitiesontheshopfloor,thatis,decidingwhenandwheretotransportapallet,whentostartaprocessonamachiningcenter,andsoon.
Themonitorfunction
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