输送机英文翻译.docx
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输送机英文翻译.docx
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输送机英文翻译
附录:
外文资料与中文翻译
外文资料:
ProductionAutomation
CharlesL.Philips,RoyceD.Harbor.FeedbackControlSystems.PrenticHall,Inc..2000
Abstract:
Automationisawidelyusedterminmanufacturing.Inthiscontext,automationcanbedefinedasatechnologyconcernedwiththeapplicationofmechanical,electronic,andcomputer-basedsystemstooperateandcontrolproduction.Examplesofthistechnologyinclude:
•Automaticmachinetoolstoprocessparts.
•Automatedtransferlinesandsimilarsequentialproductionsystems.
•Automaticassemblymachines.
•Industrialrobots.
•Automaticmaterialhandlingandstoragesystems.
•Automatedinspectionsystemsforqualitycontrol.
•Feedbackcontrolandcomputerprocesscontrol.
•Computersystemsthatautomateproceduresforplanning,datacollection,anddecisionmakingtosupportmanufacturingactivities.
Keywords:
Automationmanufacturingmechanicalcomputer
Automatedproductionsystemscanbeclassifiedintotwobasiccategories:
fixedautomationandprogrammableautomation.
FixedAutomation
FixedautomationiswhatHarderwasreferringtowhenhecoinedthewordautomation.Fixedautomationreferstoproductionsystemsinwhichthesequenceofprocessingorassemblyoperationsisfixedbytheequipmentconfigurationandcannotbereadilychangedwithoutalteringtheequipment.Althougheachoperationinthesequenceisusuallysimple,theintegrationandcoordinationofmanysimpleoperationsintoasinglesystemmakesfixedautomationcomplex.Typicalfeaturesoffixedautomationinclude1.highinitialinvestmentforcustom-engineeredequipment,2.highproductionrates,3.applicationtoproductsinwhichhighquantitiesaretobeproduced,and4.relativeinflexibilityinaccommodatingproductchanges.
Fixedautomationiseconomicallyjustifiableforproductswithhighdemandrates.Thehighinitialinvestmentintheequipmentcanbedividedoveralargenumberofunits,perhapsmillions,thusmakingtheunitcostlowcomparedwithalternativemethodsofproduction.Examplesoffixedautomationincludetransferlinesformachining,dialindexingmachines,andautomatedassemblymachines.Muchofthetechnologyinfixedautomationwasdevelopedintheautomobileindustry;thetransferline(datingtoabout(1920)isanexample.
ProgrammableAutomation
Forprogrammableautomation,theequipmentisdesignedinsuchawaythatthesequenceofproductionoperationsiscontrolledbyaprogram,i.e.,asetofcodedinstructionsthatcanbereadandinterpretedbythesystem.Thustheoperationsequencecanbereadilychangedtopermitdifferentproductconfigurationstobeproducedonthesameequipment.Someofthefeaturesthatcharacterizeprogrammableautomationinclude1.highinvestmentingeneral-purposeprogrammableequipment,2.lowerproductionratesthanfixedautomation,3.flexibilitytodealwithchangesinproductconfiguration,and4.suitedtolowand/ormediumproductionofsimilarproductsorparts(e.g.partfamilies).Examplesofprogrammableautomationincludenumericallycontrolledmachinetools,industrialrobots,andprogrammablelogiccontrollers.
Programmableproductionsystemsareoftenusedtoproducepartsorproductsinbatches.Theyareespeciallyappropriatewhenrepeatordersforbatchesofthesameproductareexpected.Toproduceeachbatchofanewproduct,thesystemmustbeprogrammedwiththesetofmachineinstructionsthatcorrespondtothatproduct.Thephysicalsetupoftheequipmentmustalsobechanged;specialfixturesmustbeattachedtothemachine,andtheappropriatetoolsmustbeloaded.Thischangeoverprocedurecanbetime-consuming.Asaresult,theusualproductioncycleforagivenbatchincludes1.a(3periodduringwhichthesetupandreprogrammingisaccomplishedand2.aperiodinwhichthebatchisprocessed.Thesetup-reprogrammingperiodconstitutesnonproductivetimeoftheautomatedsystem.
Theeconomicsofprogrammableautomationrequirethatasthesetup-reprogrammingtimeincreases,theproductionbatchsizemustbemadelargersoastospreadthecostoflostproductiontimeoveralargernumberofunits.Conversely,ifsetupandreprogrammingtimecanbereducedtozero,thebatchsizecanbereducedtoone.Thisisthetheoreticalbasisforflexibleautomation,anextensionofprogrammableautomation.Aflexibleautomatedsystemisonethatiscapableofproducingavarietyofproducts(orparts)withminimallosttimeforchangeoversfromoneproducttothenext.Thetimetoreprogramthesystemandalterthephysicalsetupisminimalandresultsinvirtuallynolostproductiontime.Consequently,thesystemiscapableofproducingvariouscombinationsandschedulesofproductsinacontinuousflow,ratherthanbatchproductionwithinterruptionsbetweenbatches.Thefeaturesofflexibleautomationare1.highinvestmentforacustom-engineeredsystem,2.continuousproductionofmixturesofproducts,3.abilitytochangeproductmixtoaccommodatechangesindemandratesforthedifferentproductsmade,4.mediumproductionrates,and5-flexibilitytodealwithproductdesignvariations.
Flexibleautomatedproductionsystemsoperateinpracticebyoneormoreofthefollowingapproaches:
1.usingpartfamilyconcepts,bywhichthepartsmadeonthesystemarelimitedinvariety;2.reprogrammingthesysteminadvanceand/oroff-line,sothatreprogrammingdoesnotinterruptproduction;3.downloadingexistingprogramstothesystemtoproducepreviouslymadepartsforwhichprogramsarealreadyprepared;)4.usingquick-changefixturessothatphysicalsetuptimeisminimized;5.usingafamilyoffixturesthathavebeendesignedforalimitednumberofpartstyles;and6.equippingthesystemwithalargenumberofquick-changetoolsthatincludethevarietyofprocessingoperationsneededtoproducethepartfamily.Fortheseapproachestobesuccessful,thevariationinthepartstylesproducedonaflexibleautomatedproductionsystemisusually)morelimitedthanabatch-typeprogrammableautomationsystem.Examplesofflexibleautomationaretheflexiblemanufacturingsystemsforperformingmachiningoperationsthatdatebacktothelate1960s.
AutomationStrategies
Anumberoffundamentalstrategiesexistforimprovingproductivityinmanufacturingoperations.Thesestrategiesofteninvolvetheuseofautomationtechnologyandare,therefore,calledautomationstrategies.Indicatingthelikelyeffectsofeachstrategyonoperatingfactorssuchascycletime,nonproductivetime,manufacturingleadtime,andotherproductionparameters.
Numericalcontrol
Numericalcontrol(oftenabbreviatedNC)canbedefinedasaformofprogrammableautomationinwhichtheprocessiscontrolledbynumbers,letters,andsymbols.InNC,thenumbersformaprogramofinstructionsdesignedforaparticularworkpartorjob.Whenthejobchanges,theprogramofinstructionsischanged.ThiscapabilitytochangetheprogramforeachnewjobiswhatgivesNCitsflexibility.Itismucheasiertowritenewprogramsthantomakemajorchangesintheproductionequipment.
NCequipmentisusedinallareasofmetalpartsfabricationandcomprisesroughly15%ofthemodernmachinetoolsinindustrytoday.Sincenumericallycontrolledmachinesareconsiderablymoreexpensivethantheirconventionalcounterparts,theassetvalueofindustrialNCmachinetoolsisproportionallymuchlargerthantheirnumbers.Equipmentutilizingnumericalcontrolhasbeendesignedtoperformsuchdiverseoperationsasdrilling,milling,turning,grinding,sheetmetalpressworking,spotwelding,arcwelding,riveting,assembly,drafting,inspection,andpartshandling.Andthisisbynomeansacompletelist.Numericalcontrolshouldbeconsideredasapossiblemodeofcontrollingtheoperationforanyproductionsituationpossessingthefollowingcharacteristics:
1.Similarworkpartsintermsofrawmaterial(e.g.,metalstockformachining).
2.Theworkpartsareproducedinvarioussizesandgeometries.
3.Theworkpartsareproducedinbatchesofsmalltomedium-sizedquantities.
4.Asequenceofsimilarprocessingstepsisrequiredtocompletetheoperationoneachworkpiece.
Manymachiningjobsmeettheseconditions.Themachinedworkpartsaremetal,theyarespecifiedinmanydifferentsizesandshapes,andmostmachinedpartsproducedinindustrytodayaremadeinsmalltomedium-sizelotsizes.Toproduceeachpart,asequenceofdrillingoperationsmayberequired,oraseriesofturningormillingoperations.ThesuitabilityofNCforthesekindsofjobsisthereasonforthetremendousgrowthofnumericalcontrolinthemetalworkingindustryoverthelast25years.
BasicComponentsofanNCSystem
Anoperationalnumericalcontrolsystemconsistsofthefollowingthreebasiccomponents:
1.Programofinstructions.
2.Controllerunit,alsocalledmachinecontrolunit(MCU).
3.Machinetoolorothercontrolledprocess.
Thegeneralrelationshipamongthethreecomponentsisillustrated.Theprogramofinstructionsservesastheinputtothecontrollerunit,whichinturncommands)themachinetoolorotherprocesstobecontrolled.
Programofinstructions
Theprogramofinstructionsisthedetailedstep-by-stepsetofdirectionswhichtelltheWmmachinetoolwhattodo.Itiscodedinnumericalorsymbolicformonsometypeofinputmediumthatcanbeinterpretedbythecontrollerunit.Themostcommoninputmediumisi-inch-widepunchedtape.Overtheyears,otherformsofinputmediahave(beenused,includingpunchedcards,magnetictape,andeven35-mmmotionpicturefilm.
TherearetwoothermethodsofinputtotheNCsystemwhichshouldbementioned.Thefirstisbymanualentryofinstructionaldatatothecontrollerunit.Thisistime-consumingandisrarelyused
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