数控外文翻译.docx

数控外文翻译.docx

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数控外文翻译

NumericalControl

Oneofthemostfundamentalconceptsintheareaofadvancedmanufacturingtechnologiesisnumericalcontrol（NC）.PriortotheadventofNC,allmachinetoolsweremanualoperatedandcontrolled.Amongthemanylimitationsassociatedwithmanualcontrolmachinetools,perhapsnoneismoreprominentthanthelimitationofoperatorskills.Withmanualcontrol,thequalityoftheproductisdirectlyrelatedtoandlimitedtotheskillsoftheoperator.Numericalcontrolrepresentsthefirstmajorstepawayfromhumancontrolofmachinetools.

Numericalcontrolmeansthecontrolofmachinetoolsandothermanufacturingsystemsthoughtheuseofprerecorded,writtensymbolicinstructions.Ratherthanoperatingamachinetool,anNCtechnicianwritesaprogramthatissuesoperationalinstructionstothemachinetool,Foramachinetooltobenumericallycontrolled,itmustbeinterfacedwithadeviceforacceptinganddecodingthep2ogrammedinstructions,knownasareader.

Numericalcontrolwasdevelopedtoovercomethelimitationofhumanoperator,andithasdoneso.Numericalcontrolmachinesaremoreaccuratethanmanuallyoperatedmachines,theycanproducepartsmoreuniformly,theyarefaster,andthelong-runtoolingcostsarelower.ThedevelopmentofNCledtothedevelopmentofseveralotherinnovationsinmanufacturingtechnology:

1.Electricaldischargemachining.

2.Lasercutting.

3.Electronbeamwelding.

Numericalcontrolhasalsomademachinetoolsmoreversatilethantheirmanuallyoperatedpredecessors.AnNCmachinetoolcanautomaticallyproduceawidevarietyofpar4s,eachinvolvinganassortmentofundertaketheproductionofproductsthatwouldnothavebeenfeasiblefromaneconomicperspectiveusingmanuallycontrolledmachinetoolsandprocesses.

Likesomanyadvancedtechnologies,NCwasborninthelaboratoriesoftheMassachusettsInstituteofTechnology.TheconceptofNCwasdevelopedintheearly1950swithfundingprovidedbytheU.SAirForce.Initsearlieststages,NCmachineswereabletomakestraightcutsefficientlyandeffectively.

However,curvedpathswereaproblembecausethemachinetoolhadtobeprogrammedtoundertakeaseriesofhorizontalandverticalstepstoproduceacurve.Theshorteristhestraightlinesmakingupthestep,thesmootheris4hecurve.Eachlinesegmentinthestepshadtobecalculated.

Thisproblemledtothedevelopmentin1959oftheAutomaticallyProgrammedTools（APT）languageforNCthatusesstatementssimilartoEnglishlanguagetodefinethepartgeometry,describethecuttingtoolconfiguration,andspecifythenecessarymotions.ThedevelopmentoftheAPTlanguagewasamajorstepforwardinthefurtherdevelopmentofNCtechnology.TheoriginalNCsystemwerevastlydifferentfromthoseusedpunchedpaper,whichwaslatertoreplacedbymagneticplastictape.Atapereaderwasusedtointerprettheinstructionswrittenonthetapeforthemachine.Together,all/fthisrepresentedgiantstepforwardinthecontrolofmachinetools.However,therewereanumberofproblemswithNCatthispointinitsdevelopment.

Amajorproblemwasthefragilityofthepunchedpapertapemedium.Itwascommonforthepapercontainingtheprogrammedinstructionstobreakortearduringamachiningprocess,Thisproblemwasexacerbatedbythefactthateachsuccessivetimeapartwasproducedonamachinetool,thepapertapecarryingtheprogrammedinstructionshadtorerunthoughtthereader.Ifitwasnecessarytoproduce100copiesofagivenpart,itwasalsonecessarytorunthepapertapethoughtthereader100separatetimes.Fragilepapertapessimplycouldnotwithstandtherigorsofshopfloorenvironmentandthiskindofrepeateduse.

Thisledtothedevelopmentofaspecialmagnetictape.Whereasthepapertapecarriedtheprogrammedinstructionsasaseriesofholespunchedinthetape,theThismostimportantofthesewasthatitwasdifficultorimpossibletochangetheinstructionsenteredonthetape.Tomakeeventhemostminoradjustmentsinaprogramofinstructions,itwasnecessarytointerruptmachiningoperationsandmakeanewtape.Itwasalsostillnecessarytorunthetapethoughtthereaderasmanytimesastherewerepartstobeproduced.Fortunately,computertechnologybecomearealityandsoonsolvedtheproblemsofNC,associatedwithpunchedpaperandplastictape.

Thedevelopmentofaconceptknownasnumericalcontrol（DNC）solvethepaperandplastictapeproblemsassociatedwithnumericalcontrolbysimplyeliminatingtapeasthemediumforcarryingtheprogrammedinstructions.Indirectnumericalcontrol,machinetoolsaretied,viaadatatransmissionlink,toahostcomputerandfedtothemachinetoolasneededviathedatatransmissionlinkage.Directnumericalcontrolrepresentedamajorstepforwardoverpunchedtapeandplastictape.How