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中英文翻译NUMERICAL CONTROL数控技术.doc

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中英文翻译NUMERICAL CONTROL数控技术.doc

NUMERICALCONTROLNUMERICALCONTROLN/CISAFORMOFPROGRAMMABLEAUTOMATIONINWHICHTHEPROCESSINGEQUIPMENTISCONTROLLEDBYMEANSOFNUMBERS,LETTERS,ANDOTHERSYMBOLS.THENUMBERS,LETTERS,ANDSYMBOLSARECODEDINANAPPROPRIATEFORMATTODEFINEAPROGRAMOFINSTRUCTIONSFORAPARTICULARWORKPARTORJOB.WHENTHEJOBCHANGES,THEPROGRAMOFINSTRUCTIONSISCHANGED.THECAPABILITYTOCHANGETHEPROGRAMISWHATMAKESN/CSUITABLEFORLOWANDMEDIUMVOLUMEPRODUCTION.ITISMUCHEASIERTOWRITEPROGRAMSTHANTOMAKEMAJORALTERATIONSOFTHEPROCESSINGEQUIPMENT.THEREARETWOBASICTYPESOFNUMERICALLYCONTROLLEDMACHINETOOLSPOINTTOPOINTANDCONTINUOUSPATHALSOCALLEDCONTOURING.POINTTOPOINTMACHINESUSEUNSYNCHRONIZEDMOTORS,WITHTHERESULTTHATTHEPOSITIONOFTHEMACHININGHEADCANBEASSUREDONLYUPONCOMPLETIONOFAMOVEMENT,ORWHILEONLYONEMOTORISRUNNING.MACHINESOFTHISTYPEAREPRINCIPALLYUSEDFORSTRAIGHTLINECUTSORFORDRILLINGORBORING.THEN/CSYSTEMCONSISTSOFTHEFOLLOWINGCOMPONENTSDATAINPUT,THETAPEREADERWITHTHECONTROLUNIT,FEEDBACKDEVICES,ANDTHEMETALCUTTINGMACHINETOOLOROTHERTYPEOFN/CEQUIPMENT.DATAINPUT,ALSOCALLED“MANTOCONTROLLINK”,MAYBEPROVIDEDTOTHEMACHINETOOLMANUALLY,ORENTIRELYBYAUTOMATICMEANS.MANUALMETHODSWHENUSEDASTHESOLESOURCEOFINPUTDATAARERESTRICTEDTOARELATIVELYSMALLNUMBEROFINPUTS.EXAMPLESOFMANUALLYOPERATEDDEVICESAREKEYBOARDDIALS,PUSHBUTTONS,SWITCHES,ORTHUMBWHEELSELECTORS.THESEARELOCATEDONACONSOLENEARTHEMACHINE.DIALSALEANALOGDEVICESUSUALLYCONNECTEDTOASYNCHROTYPERESOLVERORPOTENTIOMETER.INMOSTCASES,PUSHBUTTONS,SWITCHES,ANDOTHERSIMILARTYPESOFSELECTORSAYEDIGITALINPUTDEVICES.MANUALINPUTREQUIRESTHATTHEOPERATORSETTHECONTROLSFOREACHOPERATION.ITISASLOWANDTEDIOUSPROCESSANDISSELDOMJUSTIFIEDEXCEPTINELEMENTARYMACHININGAPPLICATIONSORINSPECIALCASES.INPRACTICALLYALLCASES,INFORMATIONISAUTOMATICALLYSUPPLIEDTOTHECONTROLUNITANDTHEMACHINETOOLBYCARDS,PUNCHEDTAPES,ORBYMAGNETICTAPE.EIGHTCHANNELPUNCHEDPAPERTAPEISTHEMOSTCOMMONLYUSEDFORMOFDATAINPUTFORCONVENTIONALN/CSYSTEMS.THECODEDINSTRUCTIONSONTHETAPECONSISTOFSECTIONSOFPUNCHEDHOLESCALLEDBLOCKS.EACHBLOCKREPRESENTSAMACHINEFUNCTION,AMACHININGOPERATION,ORACOMBINATIONOFTHETWO.THEENTIREN/CPROGRAMONATAPEISMADEUPOFANACCUMULATIONOFTHESESUCCESSIVEDATABLOCKS.PROGRAMSRESULTINGINLONGTAPESALLWOUNDONREELSLIKEMOTIONPICTUREFILM.PROGRAMSONRELATIVELYSHORTTAPESMAYBECONTINUOUSLYREPEATEDBYJOININGTHETWOENDSOFTHETAPETOFORMALOOP.ONCEINSTALLED,THETAPEISUSEDAGAINANDAGAINWITHOUTFURTHERHANDLING.INTHISCASE,THEOPERATORSIMPLYLOADSANDUNLOADSTHEPARTS.PUNCHEDTAPESALEPREPAREDONTYPEWRITERSWITHSPECIALTAPEPUNCHINGATTACHMENTSORINTAPEPUNCHINGUNITSCONNECTEDDIRECTLYTOACOMPUTERSYSTEM.TAPEPRODUCTIONISRARELYERRORFREE.ERRORSMAYBEINITIALLYCAUSEDBYTHEPARTPROGRAMMER,INCARDPUNCHINGORCOMPILATION,ORASARESULTOFPHYSICALDAMAGETOTHETAPEDURINGHANDLING,ETC.SEVERALTRIALRUNSAREOFTENNECESSARYTOREMOVEALLERRORSANDPRODUCEANACCEPTABLEWORKINGTAPE.WHILETHEDATAONTHETAPEISFEDAUTOMATICALLY,THEACTUALPROGRAMMINGSTEPSALEDONEMANUALLY.BEFORETHECODEDTAPEMAYBEPREPARED,THEPROGRAMMER,OFTENWORKINGWITHAPLANNERORAPROCESSENGINEER,MUSTSELECTTHEAPPROPRIATEN/CMACHINETOOL,DETERMINETHEKINDOFMATERIALTOBEMACHINED,CALCULATETHESPEEDSANDFEEDS,ANDDECIDEUPONTHETYPEOFTOOLINGNEEDEDTHEDIMENSIONSONTHEPARTPRINTARECLOSELYEXAMINEDTODETERMINEASUITABLEZEROREFERENCEPOINTFROMWHICHTOSTARTTHEPROGRAM.APROGRAMMANUSCRIPTISTHENWRITTENWHICHGIVESCODEDNUMERICALINSTRUCTIONSDESCRIBINGTHESEQUENCEOFOPERATIONSTHATTHEMACHINETOOLISREQUIREDTOFOLLOWTOCUTTHEPARTTOTHEDRAWINGSPECIFICATIONS.THECONTROLUNITRECEIVESANDSTORESALLCODEDDATAUNTILACOMPLETEBLOCKOFINFORMATIONHASBEENACCUMULATED.ITTHENINTERPRETSTHECODEDINSTRUCTIONANDDIRECTSTHEMACHINETOOLTHROUGHTHEREQUIREDMOTIONS.THEFUNCTIONOFTHECONTROLUNITMAYBEBETTERUNDERSTOODBYCOMPARINGITTOTHEACTIONOFADIALTELEPHONE,WHERE,ASEACHDIGITISDIALED,ITISSTORED.WHENTHEENTIRENUMBERHASBEENDIALED,THEEQUIPMENTBECOMESACTIVATEDANDTHECALLISCOMPLETED.SILICONPHOTODIODES,LOCATEDINTHETAPEREADERHEADONTHECONTROLUNIT,DETECTLIGHTASITPASSESTHROUGHTHEHOLESINTHEMOVINGTAPE.THELIGHTBEAMSARECONVERTEDTOELECTRICALENERGY,WHICHISAMPLIFIEDTOFURTHERSTRENGTHENTHESIGNAL.THESIGNALSARETHENSENTTOREGISTERSINTHECONTROLUNIT,WHEREACTUATIONSIGNALSARERELAYEDTOTHEMACHINETOOLDRIVES.SOMEPHOTOELECTRICDEVICESARECAPABLEOFREADINGATRATESUPTO1000CHARACTERSPERSECOND.HIGHREADINGRATESARENECESSARYTOMAINTAINCONTINUOUSMACHINETOOLMOTION;OTHERWISEDWELLMARKSMAYBEGENERATEDBYTHECUTTERONTHEPARTDURINGCONTOURINGOPERATIONS.THEREADINGDEVICEMUSTBECAPABLEOFREADINGDATABLOCKSATARATEFASTERTHANTHECONTROLSYSTEMCANPROCESSTHEDATA.AFEEDBACKDEVICEISASAFEGUARDUSEDONSOMEN/CINSTALLATIONSTOCONSTANTLYCOMPENSATEFORERRORSBETWEENTHECOMMANDEDPOSITIONANDTHEACTUALLOCATIONOFTHEMOVINGSLIDESOFTHEMACHINETOOL.ANN/CMACHINEEQUIPPEDWITHTHISKINDOFADIRECTFEEDBACKCHECKINGDEVICEHASWHATISKNOWNASACLOSEDLOOPSYSTEM.POSITIONINGCONTROLISACCOMPLISHEDBYASENSORWHICH,DURINGTHEACTUALOPERATION,RECORDSTHEPOSITIONOFTHESLIDESANDRELAYSTHISINFORMATIONBACKTOTHECONTROLUNIT.SIGNALSTHUSRECEIVEDALECOMPAREDTOINPUTSIGNALSONTHETAPE,ANDANYDISCREPANCYBETWEENTHEMISAUTOMATICALLYRECTIFIED.INANALTERNATIVESYSTEM,CALLEDANOPENLOOPSYSTEM,THEMACHINEISPOSITIONEDSOLELYBYSTEPPINGMOTORDRIVESINRESPONSETOCOMMANDSBYACONTROLLERS.THEREARETHREEBASICTYPESOFNCMOTIONS,ASFOLLOWSPOINTTOPOINTORPOSITIONALCONTROLINPOINTTOPOINTCONTROLTHEMACHINETOOLELEMENTSTOOLS,TABLE,ETCAREMOVEDTOPROGRAMMEDLOCATIONSANDTHEMACHININGOPERATIONSPERFORMEDAFTERTHEMOTIONSARECOMPLETEDTHEPATHORSPEEDOFMOVEMENTBETWEENLOCATIONSISUNIMPORTANT;ONLYTHECOORDINATESOFTHEENDPOINTSOFTHEMOTIONSAREACCURATELYCONTROLLEDTHISTYPEOFCONTROLISSUITABLEFORDRILLPRESSESANDSOMEBORINGMACHINES,WHEREDRILLING,TAPPING,ORBORINGOPERATIONSMUSTBEPERFORMEDATVARIOUSLOCATIONSONTHEWORKPIECESTRAIGHTLINEORLINEARCONTROLSTRAIGHTLINECONTROLSYSTEMSAREABLETOMOVETHECUTTINGTOOLPARALLELTOONEOFTHEMAJORAXESOFTHEMACHINETOOLATACONTROLLEDRATESUITABLEFORMACHININGITISNORMALLYONLYPOSSIBLETOMOVEINONEDIRECTIONATATIME,SOANGULARCUTSONTHEWORKPIECEARENOTPOSSIBLE,CONSEQUENTLY,FORMILLINGMACHINES,ONLYRECTANGULARCONFIGURATIONSCANBEMACHINEDORFORLATHESONLYSURFACESPARALLELORPERPENDICULARTOTHESPINDLEAXISCANBEMACHINEDTHISTYPEOFCONTROLLEDMOTIONISOFTENREFERREDTOASLINEARCONTROLORAHALFAXISOFCONTROLMACHINESWITHTHISFORMOFCONTROLAREALSOCAPABLEOFPOINTTOPOINTCONTROLCONTINUOUSPATHORCONTOURINGCONTROLINCONTINUOUSPATHCONTROLTHEMOTIONSOFTWOORMOREOFTHEMACHINEAXESARECONTROLLEDSIMULTANEOUSLY,SOTHATTHEPOSITIONANDVELOCITYOFTHECANBETOOLARECHANGEDCONTINUOUSLYINTHISWAYCURVESANDSURFACESCANBEMACHINEDATACONTROLLEDFEEDRATEITISTHEFUNCTIONOFTHEINTERPOLATORINTHECONTROLLERTODETERMINETHEINCREMENTSOFTHEINDIVIDUALCONTROLLEDAXESOFTHEMACHINESNECESSARYTOPRODUCETHEDESIREDMOTIONTHISTYPEOFCONTROLISREFERREDTOASCONTINUOUSCONTROLORAFULLAXISOFCONTROLSOMETERMINOLOGYCONCERNINGCONTROLLEDMOTIONSFORNCMACHINESHASBEENINTRODUCEDFOREXAMPLE,SOMEMACHINESAREREFERREDTOASFOURORFIVEOREVENSIXAXISMACHINESFORAVERTICALMILLINGMACHINETHREEAXESOFCONTROLAREFAIRLYOBVIOUS,THESEBEINGTHEUSUALX,Y,ZCOORDINATEDIRECTIONSAFOURTHORFIFTHAXISOFCONTROLWOULDIMPLYSOMEFORMOFROTARYTABLETOINDEXTHEWORKPIECEORPOSSIBLYTOPROVIDEANGULARMOTIONOFTHEWORKHEADTHUS,INNCTERMINOLOGYANAXISOFCONTROLISANYCONTROLLEDMOTIONOFTHEMACHINEELEMENTSSPINDLES,TABLES,ETCAFURTHERCOMPLICATIONISUSEOFTHETERMHALFAXISOFCONTROL;FOREXAMPLE,MANYMILLINGMACHINESAREREFERREDTOAS25AXISMACHINETHISMEANSTHATCONTINUOUSCONTROLISPOSSIBLEFORTWOMOTIONSAXESANDONLYLINEARCONTROLISPOSSIBLEFORTHETHIRDAXISAPPLIEDTOVERTICALMILLINGMACHINES,25AXISCONTROLMEANSCONTOURINGINTHEX,YPLANEANDLINEARMOTIONONLYINTHEZDIRECTIONWITHTHESEMACHINESTHREEDIMENSIONALOBJECTSHAVETOBEMACHINEDWITHWATERLINESAROUNDTHESURFACEATDIFFERENTHEIGHTSWITHANALTERNATIVETERMINOLOGYTHESAMEMACHINECOULDBECALLEDA2CLMACHINECFORCONTINUOUS,LFORLINEARCONTROLTHUS,AMILLINGMACHINEWITHCONTINUOUSCONTROLINTHEX,Y,ZDIRECTIONSCOULDBETERMEDBEATHREEAXISMACHINEORA3CMACHINE,SIMILARLY,LATHESAREUSUALLYTWOAXISOR2CMACHINESTHEDEGREEOFWORKPRECISIONDEPENDSALMOSTENTIRELYUPONTHEACCURACYOFTHELEADSCREWANDTHERIGIDITYOFTHEMACHINESTRUCTURE.WITHTHISSYSTEM.THEREISNOSELFCORRECTINGACTIONORFEEDBACKOFINFORMATIONTOTHECONTROLUNIT.INTHEEVENTOFANUNEXPECTEDMALFUNCTION,THECONTROLUNITCONTINUESTOPUTOUTPULSESOFELECTRICALCURRENT.IF,FOREXAMPLE,THETABLEONAN/CMILLINGMACHINEWERESUDDENLYTOBECOMEOVERLOADED,NORESPONSEWOULDBESENTBACKTOTHECONTROLLER.BECAUSESTEPPINGMOTORSARENOTSENSITIVETOLOADVARIATIONS,MANYN/CSYSTEMSAREDESIGNEDTOPERMITTHEMOTORSTOSTALLWHENTHERESISTINGTORQUEEXCEEDSTHEMOTORTORQUE.OTHERSYSTEMSAREINUSE,HOWEVER,

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