毕设英文翻译.docx

毕设英文翻译.docx

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毕设英文翻译

MAINTENANCEENGINEERING

Itisessentialforafactorytomaintainitsequipmentinordertoproduceaproductwithinanacceptablecostandtimeperiod.Iftheequipmentinthefactoryiserraticinperformance,onlyanunderoptimalresultcanbeobtained.Howerratictheequipmentperformanceis,willdeterminethedegreeofunderoptimaloperation.Themissionofmaintenanceengineeringistoseverelydepresstheoccurrencesoferraticequipmentperformance,therebyminimizinganegativeproductivityfactor.

Thebasictaskofmaintenanceengineeringistodeveloppreventiveroutinesforequipmentsothatitiscapableofrunningtospecificdesignrequirements.Thismeansthatmaintenanceengineeringisinterestedindeterminingwhatchecks,inspections,andreplacementofpartsshouldbeperformedduringscheduleddowntimessothatthemachinesrunasdesignedandunscheduleddowntimesareprevented.However,whenbreakdownsoccurtheunitmustreactquicklytoreturn

theaffectedequipmenttoservice.Asecondaryobjectiveofmaintenanceengineeringistokeepthefacilitiesandofficespacesingoodrepairtofosterexcellentemployeemorale.Withtheseobjectivesinmind,letusexaminethetechniquesusedbythemaintenanceengineeringunit.

ASSIGNEDTOMAINTENANCEENGINEERING

Fourbasictasksareassignedtomaintenanceengineering:

1.Preventivemaintenance

2.Rapidemergencyrepair

3.Toolroomactivities

4.Buildingsandgroundsmaintenance

Allfouractivitiescanrequireawidevarietyofengineeringdisciplinestoachievesuccessfulresults.Whenmakingrepairstomachinetools,theskillsandknowledgeofelectronicengineeringmayberequiredtodiagnoseaComputerNumericalControl（CNC）problem,andthoseofmechanicalengineeringmaybenecessarytodeterminetherisksofbearinginstabilityifasubstitutelubricatingoilisused.

Inemergencyrepairworkitiscommontomakereplacementpartsinthetoolroomwithouthavingthevendor’sdetaileddrawings,sothatthemaintenanceengineerbecomesadesignengineer,producibilityengineer,andmethodsengineerallatthesametime.Themaintenanceengineermusthavemorethanpassingcompetenceintheseareasiftherepairpartsaretoworkandtheequipmentrunagain.Wecanseethatmaintenanceengineeringiscomplexandchallenging.Ioftenthinkofmaintenanceengineersastheland-basedequivalentofshipboardmarineengineerswhocankeepashipafloatandoperationalinwhatappeartobeimpossiblecircumstances.Thetruemaintenanceengineerisofthesamemold:

creative,resourceful,andpossessingapositiveattitudetowardkeepingtheequipmentoperational.Managementofmaintenanceengineeringtheninvolvescreatingasystemofcontrolsandreportingwithinwhichtheseengineerscanoperateeffectively.Beforeexaminingmaintenanceengineeringmanagementtechniques,letusreviewthefourbasictasksofthemaintenanceengineeringunit.

PreventiveMaintenance

Thebasicgoalofmaintenanceengineeringistopreventunscheduledshutdownofequipmentduetofailure.Therefore,preventivemaintenanceisaprimaryactivityoftheunit.

Successfulpreventivemaintenancerequiresapreciseandthoroughunderstandingoftheequipmentusedinmakingthecompany’sproducts.Thisincludesunderstandingthedesignphilosophyoftheequipment,includingwhatmakesitworkandwhatmustbeconsideredtheweaklinksofthesystem,andunderstandinghowtheequipmentistobeusedinthefactory.Thisdualviewofdesignuseversusactualusesetsthetoneforhowpreventivemaintenancewillbeapplied.

EXAMPLE（a）:

Supposethatalathedesignedtocarryaloadofupto600lbistobeusedfrequentlyatorslightlyabovethisload.Whatwouldthepreventivemaintenanceschemebelike?

Obviously,operatingaboverecommendedloadlevelsisnotthebestidea,butoccasionallyafirmconsiderstheriskofoverloadingpreferabletoanexpenditureofcapitalfundstopurchasedifferentequipment.Managementinthiscaseisdecidingtocutintotheequipment’sfactorofsafety,recognizingthattheloadratewassetconservativelylowbythevendortoprotectagainstwarrantyfailure.Therefore,themaintenanceengineerwouldlookfortheweaklinksinthelathedesignandschedulethemforfrequentexaminationsandpossiblyreplacementofpartsbeforeafailureoccurs.Thedesign’sweakestlinkwouldprobablybethebearingsofthemachine,becausetheyarebeingaskedtocarryacontinuousoverload.Therefore,afteracertainperiodofoperatingtimethebearingswouldbeinspected,andafteralongerperiodthenextweakestlinkalongwiththebearingswouldbeinspected,andsoforth,untilatimeintervalwasreachedwherethebearingswouldbereplacedbeforeafailureoccurred.Thereplacementtimewouldbedeterminedbycalculatingtheexpectedbearinglifewiththesustainedoverload.

Intheaboveexample,theweakestlinkwasidentifiedandapreventivemaintenanceprogramwasdesignedtofittheuser’sspecificcircumstances.

EXAMPLE（b）:

Ifthelathewastobeusedcommonlyforfarlighterpieces,thenapreventivemaintenanceprogrammighthavebeenfocusedonotherthings—perhapsthelubricationsystemstomakesureoillinesarenotplugged—andthebearingslookedatonlyrarely.Heretheusagedictatesexaminingnotload-carryingcomponentsbutsystemscomponents.

Theseexamplesshowthatmaintenanceengineeringcannotsimplyfollowvendor-suggested

preventivemaintenancetechniquesandignorethespecificutilizationoftheequipment.Preventivemaintenancetechniquessuggestedbyvendorsarebasedonageneralizedconceptoftheuseoftheequipmentandadesiretoprotectthemselvesfromnegligencelawsuits.Therefore,maintenanceengineeringshouldusethevendor’stechniquesasguidelinesbutnotasrigidrequirements.

Intheseexamplesoperationalpartsaresometimesreplacedbeforetheyfail.Thisisdonetocontroldowntimesandnotletfailuredictatewhenmachinesarenotusable.Manypartsthatappeartobeusablehavereachedtheendoftheirstatisticallyusablelivesandareinimminentdangeroffailing.Goodpreventivemaintenanceisbasedonknowingtheusefullifeofcomponentsandreplacingthempriortofailure.

Thetechniquesfordeterminingtheeffectivelifeofcomponentparts,suchasrollerbearings,arewellknownandarecoveredextensivelyintextbooksonmachinedesign.Maintenanceengineersarecompetentinthesetechniques.However,thebodyofknowledgeappliedbymaintenanceengineersencompassesvirtuallytheentirespectrumofengineering.Whatisnecessaryinaparticularcompanydependsonthetypeofproductbeingmanufacturedandthetypeofequipmentused.Inanelectronicassemblyoperationwewouldexpecttofindautomatedequipmentandtheequipmentcontainingelectroniccircuits,especiallyfortesting.Therefore,thebasicskillsemployedbythemaintenanceengineerwouldbethoseofanelectronicsengineer.Similarly,afactoryproducingartificialfabricswouldbebasicallyachemicalplant,andthemaintenanceengineerwouldbeskilledinchemicalengineeringtechniquesandperhapsthefluidflowtechniquesofmechanicalengineering.

RapidEmergencyRepair

Mostpeoplethinkofemergencyrepairasthefocusofmaintenanceengineering.However,liketheemergencyroomofahospital,itdoesnotrepresentallthetechniquesandservicesrepresented,andisnotthepreferredmethodoftreatment.

Rapidemergencyrepairistheultimatefallbackpositionofthemaintenanceengineeringunit.Ifprogramsofpreventivemaintenancefail,oranaccidentoccurs,oranoperatorerrorresultsinmachinefailure,theonlypracticalrecourseisrepairinthemostexpeditiousandeconomicmanner.Theonlyalternativetorepairistoscraptheequipmentandreplaceit.Ifthisisthecase,themaintenanceengineeringunit’sinvolvementcomestoanendandtheprojectisassignedtoadvancedmanufacturingengineering.Sincethelatterisasignificantlyrareroccurrencethanmakingtherequiredrepair,letuslookatthephilosophyofemergencyrepairandseehowitaffectstheactionsofthemaintenanceengineeringunit.Rememberthatthisisemergencyrepair,notrepairsmadeaspartofaplanneddowntimewheretheactivityhasbeenextensivelyplanned.

Thefirstaspectofemergencyrepairisthattherecanbenospecificpreplanning.Thenatureoftherepairscanvarywidely,andtheexactrequirementsareneverknownuntiltheneedforanemergencyrepairbecomesevident.Thismeansthatthemaintenanceengineeringunitmustbecompetenttohandlealargevarietyofrepairsandbestockedinageneralsensewithawidevarietyofrepairmaterials.Thisbroadnessofapplicationisoftenaproblemindeterminingstockinglevelsforspareparts.Howmanysizesofpressureregulatorsorcapacitorscanthemaintenanceengineeringunitaffordtostock?

Thinkofhowoftenhomerepairsarethwartedbecausethejarofscrewsandnutsdoesnotcontainoneoftheproperlength,diameter,orthreadpitch.Thesameisoftentrueinfactoryrepairactivities.Tominimizetheneedtostockavarietyofsizes,maintenanceengineeringmakessurethatAMEknowswhatcomponentsforallequipmentshouldbestandardized,downtothelevelofthreadsizesandelectricalhardware.Oneofthecriticalfactorsinbeingabletoeffectivelycopewithemergencyrepairistohaveawell-stockedinventoryofgeneralizedandstandardizedspareparts.

Thesecondaspectofsuccessfulemergencyrepairistheabilitytodiagnosetheproblemquicklyandcorrectly.Thishasalargeimpactontheeconomicsofthefactory.Amachinethatisdowncoststhecompanyproductivecapacity,hencelostprofitability.Machinesusuallycostintheneighborhoodof$150perhourtorun,sothateveryex