机械制造专业毕业设计外文翻译制造分析.docx

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