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6FlexibleManufacturingAsanintroductiontothesubsequentdiscussionsofproductionsystemsandadvancedmanufacturingtechnologiesitisusefultopresentadefinitionofthetermmanufacturingsystem.Amanufacturingsystemcanbedefinedasaseriesofvalue-addingmanufacturingprocessesconvertingtherawmaterialsintomoreusefulformsandeventuallyfinishedproducts.)11Inthemodemmanufacturingsetting,flexibilityisanimportantcharacteristic.Itmeansthatamanufacturingsystemisversatileandadaptable,whilealsocapableofhandlingrelativelyhighproductionruns.Aflexiblemanufacturingsystemisversatileinthatitcanproduceavarietyofparts.Itisadaptablebecauseitcanbequicklymodifiedtoproduceacompletelydifferentlineofparts.Aflexiblemanufacturingsystem(FMS)isanindividualmachineorgroupofmachinesservedbyanautomatedmaterialshandlingsystemthatiscomputercontrolledandhasatoolhandlingcapability.Becauseofitstoolhandlingcapabilityandcomputercontrol,suchasystemcanbecontinuallyreconfiguredtomanufactureawidevarietyofparts.Thisiswhyitiscalledaflexiblemanufacturingsystem.Flexiblemanufacturingrepresentsamajorsteptowardthegoaloffullyintegratedmanufacturing.Itinvolvesintegrationofautomatedproductionprocesses.Inflexiblemanufacturing,theautomatedmanufacturingmachine(i.e.,lathe,mill,drill)andtheautomatedmaterialshandlingsystemshareinstantaneouscommunicationviaacomputernetwork.Fig.6.1isanexampleofaflexiblemanufacturingsystem.Flexiblemanufacturingtakesamajorsteptowardthegoaloffullyintegratedmanufacturingbyintegratingseveralautomatedmanufacturingconcepts:(1)Computernumericalcontrol(CNC)ofindividualmachinetools.(2)Distributednumericalcontrol(DNC)ofmanufacturingsystems.(3)Automatedmaterialshandlingsystems.(4)Grouptechnology(familiesofparts).Whentheseautomatedprocesses,machines,andconceptsarebroughttogetherinoneintegratedsystem,anFMSistheresult.HumansandcomputersplaymajorrolesinanFMS.Theamountofhumanlaborismuchlessthanwithamanuallyoperatedmanufacturingsystem,ofcourse.However,humansstillplayavitalroleintheoperationofanFMS.Humantasksincludethefollowing:(1)Equipmenttroubleshooting,maintenance,andrepair.(2)Toolchangingandsetup.(3)Loadingandunloadingthesystem.(4)Datainput.(5)Changingofpartsprograms.(6)Developmentofprograms.Flexiblemanufacturingsystemequipment,likeallmanufacturingequipment,mustbemonitoredforbugs,malfunctions,andbreakdowns.Whenaproblemisdiscovered,ahumantroubleshootermustidentifyitssourceandprescribecorrectivemeasures.Evenwhenallsystemsareproperlyfunctioning,periodicmaintenanceisnecessary.Humanoperatorsalsosetupmachines,changetools,andreconfiguresystemsasnecessary.ThetoolhandlingcapabilityofanFMSincreases,butdoesnoteliminatehumaninvolvementintoolchangingandsetup.ThesameistrueofloadingandunloadingtheFMS.Oncerawmaterialhasbeenloadedontotheautomatedmaterialshandlingsystem,itismovedthroughthesystemintheprescribedmanner.However,theoriginalloadingontothematerialshandlingsystemisstillusuallydonebyhumanoperators,asistheunloadingoffinishedproducts.Humansarcalsoneededforinteractionwiththecomputer.HumansdeveloppartprogramsthatcontroltheFMSviacomputers.TheyalsochangetheprogramsasnecessarywhenreconfiguringtheFMStoproduceanothertypeofpartorparts.Humansplaylesslabor-intensiverolesinanFMS,buttherolesarcstillcritical.ControlatalllevelsinanFMSisprovidedbycomputers.IndividualmachinetoolswithinanFMSarecontrolledbyCNC.TheoverallsystemiscontrolledbyDNC.Theautomatedmaterialshandlingsystemiscomputercontrolled,asareotherfunctionsincludingdatacollection,systemmonitoring,toolcontrol,andtrafficcontrol.Human/computerinteractionisthekeytotheflexibilityofanFMS.6.1HistoricalDevelopmentofFlexibleManufacturingFlexiblemanufacturingwasborninthemid-1960swhentheBritishfirmMolins,Ltd.developeditsSystem24.System24wasarealFMS.However,itwasdoomedfromtheoutsetbecauseautomation,integration,andcomputercontroltechnologyhadnotyetbeendevelopedtothepointwheretheycouldproperlysupportthesystem.ThefirstFMSwasadevelopmentthatwasaheadofitstime.Assuch,itwaseventuallydiscardedasunworkable.Flexiblemanufacturingremainedanacademicconceptremainderofthe1960sand1970s.However,withthethroughemergencesophisticatedcomputercontroltechnologyinthelate1970sandearly1980s,flexiblemanufacturingbecameaviableconcept.ThefirstmajorusersofflexiblemanufacturingintheUnitedStatesweremanufacturersofautomobiles,trucks,andtractors.6.2RationaleforFlexibleManufacturingInmanufacturingtherehavealwaysbeentradeoffsbetweenproductionratesandflexibility.Atoneendoftheissuearetransferlinescapableofhighproductionrates,butlowflexibility.AttheotherendoftheissueareindependentCNCmachinesthatoffermaximumflexibility,butarecapableonlyoflowproductionrates.Flexiblemanufacturingfallsinthemiddle.Therehasalwaysbeenaneedinmanufacturingforasystemthatcouldproducehighervolumeandproductionrunsthancouldindependentmachines,whilestillmaintainingflexibility.Transferlinesarecapableofproducinglargevolumesofpartsathighproductionrates.Thelinetakesagreatdealofsetup,butcanturnoutidenticalpartsinlargequantities.Itschiefshortcomingisthatevenminordesignchangesinapartcancausetheentirelinetobeshutdownandreconfigu