机械制造专业毕业设计外文翻译制造分析.docx
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机械制造专业毕业设计外文翻译制造分析
MANUFACTURINGANALYSIS:
HOWMUCHFLEXIBILITY?
Inadditiontoproductionsystemsthatfabricateveryhighqualityproducts,atlowcost,andwithultrarapiddelivery,manystrategicplannersandeconomistspointtotheneedforflexibility.
PublicationsfromJapan(Yoshio,1994;Ohsono,1995)expressasimilarview,andthemorerecentJ.D.Powerscomparativesurveysonautomobilesindicatethat"nowthatothersareclosingthequalitygap,theJapanesehavetocompeteinotherareas"(seeRechtin,1994;andtheannualJ.D.Powersreportseries).Emphasisisthusplaceonthesecombinedfactorsofquality,cost,delivery,andflexibility(QCDF).Theabilitytoreacttosmallerlotsizesandthequestforultrarapiddeliveryaremajorconconcerns,culminatinginthepossbilityofathree-daycar(Iwataetal.,1990_.
Inanidealsituation,oncethevariousmarketsectorshavebeenestablished,productionwillsettleintoagrooveandbeconstantlyrefinedandimprovedbutwithnomajorupheavals.Unfortunately,inrecentyears,manufacturershavenotbeenabletorelyonlongperiodsofuninterruptedproductionbecauseeventsintheworldeconomyhaveforcedrapidchangesinconsumerdemandandtherangeofconsumerpreferences.
HenryFord"sfavoriteaphorism-thathiscutomerscouldhaveanycolorofcartheywantedaslongasitwasblack-isinsharpcontrasttotoday'srangeofconsumerpreferences.Thishasledtotheproposalbysomeacademicsthatmanufacteringcanbebuiltfor"customizedmassproduction."Thissoundsniceonfirsthearing.Howerver,forproductslikeautomobiles,thedegreeofcustomizationcangoonlysofarforagivenbatchsizeandpricepoint.OnlyhyperwealthyCEOsandmoviestarscangetprecisecustomizationinproductslikeautomobiles.
Nevertheless,anabilitytobepreparedforanysuddenmarketshiftsisbecomingmoreofanissue.Asnewequipmentispurchased,manufacturingcompaniesmustdecidebetweenharwarethatisdedicatetoonlyafewtasksandisthusrelativelyinexpensive,andmorecostlybutmoreversatileequipmentthatmightperformunforeseentasksinthefuture.Themethodologiesforanalyzingcapitalexpenditures,returns=on-investment(ROI),anddepreciationsaregiveninmanytexts(seeParkin,1992).
thesecanbeusedtoanalyzetheROIfornewmachinerythathasbeenidentifiedasusefulandisthereforeabouttobepurchased.However,sincetoday'smarkettrendsaresouncertain,suchanalysesdonothelptopredictthespecificsystemstoinstallinthefirtplace.Thehopeisthatsomeoftheengineeringsolutionswillprovidemuchmoreflexiblemachineryforonlyamodestincreaseincost(Greeenfeldetal.,1989).Inthisway,theinvestmentdilemnamightbelesscritical.
Theprecedingdiscussionsemphasizethatflexibilityisamainchallengeforthecontinuedgrowthofamewcompany.Themainquestionis:
Canadesignandfabricationsystemthatisfirstsetuptorespondtoonemarketsectorbequicklyreconfiquredtorespondtotheneedsofanothermarketsector,orevenanotherproduct,andbejustasefficient?
Today,theanswertothisquestionis"probablynot."Forexample,ifamachineshopiswellequippedwithlathesbuthasnoverticalboringmachines,therewillbeanaturallimitonachievabletolerances.Itisunlikelythatitwillbeabletosuddenlyjumpfromtrucktransmissionstohelicopterteansmissions.Andeveninthereversescenario,ifashophasdedicateditselftoprecisionboring.itisunlikelythattheequipmentandthecraftspeoplewillbeabletobrquicklyredeployedinacost-effectivemannertoroutineproductionproceduresandlessdemandingtolerances;theircompetitiveadvantagewouldbelost.Thesesamecomparisonscanbemadeforsemiconductormanufacturing.Manufacturerswhoarecurrentlyfocusingonthehigh-volumeproductionofmemorychipswillnotreadilyswitchtoapplication-specificdevicesorveceversa.Thegeneralconclusionmaybedrawnthattoday'smanufacturingtools-specificallymanufacturingsystems-arestilltoodedicatedtospecificmachinetools,robots,andmanuvacturingsystems-arestilltoodedicatedyospecificmarketsectorsandarenotflexibleenough.
Thisgeneralneedforflexibl,reconfigurablemanufacturingsystemswasofcourseakeyaspectofCIMiitsoriginalxonception.Merchant(1980)ledanumberofindustyforecastsbetween1969and1971thatrefinedthedetailsandneedsoftheCIMphilosophy.However,theseforecastsoverestimatedtherateatwhichflexiblemanufacturingsystemsangrelatedtechnologywouldbeasorbedintofactories.Duringthe1970sand1980s,machinesexchanged”handshakes”whentaskswerecompleted.Ifthesetaskswerecompletesproperlyandontim,thenaflexiblemanufacturingsystem(FMS)continuedtooperatesatisfactorily.However,ifthemachineswentseriouslyoutofbounds,thenthecommunicaationsbrokedownandtoofrequenthumaninterventionwasneededtomaketheFMSefficient.Duringthisera,theexperiencesofseveralresearchanddevelopmentgroupsshowedthattheinadequacyofcellcommunicationsoftwarewasprobablythekeyimpedimenttotheindustrialacceptanceofCIM(Harrington,1973;Merchant,1980;Bjorke,1979).Ofinterestwasthatbythelate1980s.thereviewarticlesonCIMwereadvocatingmuchsmallerFMSsofonlythreeorfourmaxhinesasthemostefficientwayofutilizingthecellconcept.Allthesetrenssuggestesmoresophisticatedcomputer-andsensorbasedtechniquesatthefactoryfloor.asdescribedlater.
2.6.1DesignforFlexibility(Reuse)
Designforflexibilityintheautomobileindustrycanpayoffinabigwayifthereissomereusabilityoffixturefamilies.Theautomatedassemblylineswheretheframes,doors,andchassisareasembledwithrobotsandweldedtogetherareobviouslyintenselyexpensive.Thesearesualltwo_story-highlinesasbigasmanyfootballfieldswhererobots,fixtures,andalignmentcradlesbringthebodycomponentstogetherforweldingandassemblu.Theintensecostoftheselinesishardtopicturewithoutavisittoastandardautomobileplant.Thekeyissueistomaximizetheuseandreuseofthesefixuringlines.Ifdesigerswereallowedtotalfreedom,eachvehicleinthefamilumightrequirespecialtooling,Thiswouldnotallowcost-effectivemanufacturing.Asmintionedearlier.thisfactorplacesanimportantresponsibilityonthedesigner.Inanidealsituationthenewlydesignedcomponentwillbemadeonexisigfactory-floormachinery,readilyleadingtoan“off_the-shelf”automationsolution,Inthebestcase,existingfixturesandevensomepartsofexistingdieswillalsoreused.
Somecompanies,thosewithsmallerbatchsizes,mightuseamixedproductionline.Asoneviewssuchaline,severalbodystylesgoby:
perhapsthemixisassimpleasregularsedansandstationwagons.butthemixcanoftenbestretchedbeyondthistodufferentcarsofmoreorlessthesamesize.Withgooddesignformultipleusability,manyofthehardfixturesandrobotscahbeusedgorallthedifferingvehiclesinthefamily.
Also,withgoodcooperationbetweenmanufacturinganddesign,theexistingrobotsandfixturesmightevenbeableto“upwardlyconstrainthevehicledesignspace”foorfuturevehickes.Therefore,viewedacrossseveralyearsandmorethanonefamilyofvehickes,automationcostsarerelativelylowerperindevidualvehicle
2.62ConcludingRemarks:
designAestheticsversusManufacturing
Justtokeepaproperperspectiveatthecloseofthissubsection,itmustveemphasizedthatdesignformanufacturability(orflxibility)hastobeprudentlyapp;iedwiththeperceivedenduserconstantlyinmind,TheJapanesearticlesconcernedwithTQM(Yoshio,1994;Iwataetal.,1990;seeHaiserandClausing,1988)increasinglyemphasizethemorequalitativeaspectsofaestheticsasoneoftheirnextthrusts,eventhoughthisismuchmoredefficulttomeasureasadesignobjective.
Atoneextreme,acomponentthatisdestinedtobeburiesdeepinacar,awashingmachine,orafurnacedoesnotneedtolookgood.DFMandDFAmethodscanbeappliedatverystepinFigure2.1.
Atoneextreme,therewillalwaysbeamarketforhigh-qualityexpensiveproductssuchasthe$300poloshirtdisscussedinSection2.4.10,anewJaguar,oranexpensiveBangandOlfsonmusicsystem.Inthesecasesthebuyerisactivelyseekingstyleandluxury.Therefore,thedesign-for-manufacturabilityengineerscannothaveitalltheirownway,oracarmightendup;ookinglkearectangularboxonfourwheels:
cheap,itistrue,buthardtosell.
Toconcludewithpersonalobservations,itisckearfromvisitstoTokyoandKyotothatwealthyJapanesepeoplepreferaMercdesBenz,.aBM,aJaguar,orthelargeTootasandAccuras.NotmanyAmericancarsareseenonthestreets,eveninthefinancialdistrictsandembassyareasofYokyo.OnedoesseetheoccasionalCadillac,somefullyloadedJeeps,andsomeofthenewerFordMustangs,butnotmany.
The”BigThree”U.S.companiescomplainthatthereasonforthisisthatJapanimposestradebarriersonU.S.vehicles.However,perhapstherealreasonisthatawealthyJapanesebusinessmanwantsacarwithbrando.ThisusaJapanesephrasemeaning“brandappeal.”So,perhapsU.S.carsinJapanjustdonothaveenoughbrandoatthepresenttime.Afterall,JapanisswampedwuthitherU.S.productsthatdohavebrando:
Lecu’s501,McDonald’sHollywoodactionmovies,andCDsbyAmericanmusicians.And,inevitably,theStarbuck’sCoffeeshopsinTokyoareswamped.
Themoralofthestoryisthatproductdesignandproductmanufacturinghaveartandirrationalemotionslurkingintheircornersthatdesignandmanufacturingengineersshouldnotignore.
2.7MANAGEMENTOFTECHNOLOGY
Chapter1reviewedtheart,technology,science,andbusinessofmanufacturing,.Duringthelast100yearsdesignandmanufacturinghaveclearlymovedfromanart/technologyendeavortoabusiness/scienceendeavor.Empatically,inthisnew