1、1NumericalControlWithChinabeingfasttobecomeglobalmanufacturingcenter/ofourcountrymanufacturingindustryinrecentyearsdevelopswiftandviolent/numericalcontrolisitbecomemarketcompetitionandenterprisedevelopmentnewandonalreadytoprocess/CADandmanufacture(CAD/CAM)becomeahotissueofthemechanicalmanufacturingi
2、ndustry/Oneofthemostfundamentalconceptsintheareaofadvancedmanufacturingtechnologiesisnumericalcontrol(NC)/PriortotheadventofNC/allmachinetoolsweremanuallyoperatedandcontrolled/Amongthemanylimitationsassociatedwithmanualcontrolmachinetools/perhapsnoneismoreprominentthanthelimitationofoperatorskills/W
3、ithmanualcontrol/thequalityoftheproductisdirectlyrelatedtoandlimitedtotheskillsoftheoperator/Numericalcontrolrepresentsthefirstmajorstepawayfromhumancontrolofmachinetools/Numericalcontrolofmachinetoolsisreportedtohavebeenfirstdevelopedbetween1947and1952attheMassachusettsinstituteofTechnology/inconju
4、nctionwiththeParsonsAircraftCorporation/Thedevelopmentofnumericalcontroltechniquesisaccreditedtotheneedforproducingveryaccuratelysizedandintricatelyshapedpartsforaircraft/principallyspacevehicles/Becauseofthecomplexshapes/considerabletimeswasbeingspentinensuringthatthework/toolrelationshipwascorrect
5、beforemachiningtookplace；thisledtolongmanufacturingtimesandhencehighcosts/Inordertoreducecosts/attemptsweremadetocontrolautomaticallythework/toolrelationship/ThisresultedinthedevelopmentofpositionalcontrolusingnumericalprinciplesonaCincinnatiHydrotelverticalmill/Numericalcontrolmeansthecontrolofmach
6、inetoolsandothermanufacturingsystemsthroughtheuseofprerecorded/writtensymbolicinstructions/Ratherthanoperatingamachinetool/anNCtechnicianwritesaprogramthatissuesoperationalinstructionstothemachinetool/Foramachinetooltobenumericallycontrolled/itmustbeinterfacedwithadeviceforacceptinganddecodingthepro
7、grammedinstructions/knownasareaderNumericalcontrolwasdevelopedtoovercomethelimitationofhumanoperators/andithasdoneso/Numericalcontrolmachinesaremoreaccuratethanmanuallyoperatedmachines/theycanproducepartsmoreuniformly/theyarefaster/andthelong-runtoolingcostsarelower/ThedevelopmentofNCledtothedevelop
8、mentof2severalotherinnovationsinmanufacturingtechnology/Electricaldischargemachining/Lasercutting/Electronbeamwelding/Numericalcontrolhasalsomademachinetoolsmoreversatilethantheirmanuallyoperatedpredecessors/anNCmachinetoolcanautomaticallyproduceawidevarietyofparts/eachinvolvingancontrolhasallowedma
9、nufacturerstoundertaketheproductionofproductsthatwouldnothavebeenfeasiblefromaneconomicperspectiveusingmanuallycontrolledmachinetoolsandprocesses/Likesomanyadvancedtechnologies/NCwasborninthelaboratoriesoftheMassachusettsInstituteofTechnology/TheconceptofNCwasdevelopedintheearly1950swithfundingprovi
10、dedbytheU/S/AirForce/Initsearlieststages/NCmachinesereabletomakestraightcutsefficientlyandeffectively/However/curvedpathswereaproblembecausethemachinetoolhadtobeprogrammedtoundertakeaseriesofhorizontalandverticalstepstoproduceacurve/theshorterthestraightlinesmakingupthesteps/thesmootheristhecurve/Ea
11、chlinesegmentinthestepshadtobecalculated/Thisproblemledtothedevelopmentin1959oftheAutomaticallyProgrammedTools(APT)language/ThisisaspecialprogramminglanguageforNCthatusesstatementssimilartoEnglishlanguagetodefinethepartgeometry/describethecuttingtoolconfiguration/andspecifythenecessarymotions/Thedev
12、elopmentoftheAPTlanguagewasamajorstepforwardinthefurtherdevelopmentofNCtechnology/TheoriginalNCsystemswerevastlydifferentformthoseusedtoday/Themachineshadhardwiredlogiccircuits/Theinstructionalprogramswerewrittenonpunchedpaper/whichwaslatertobereplacedbymagneticplastictape/Atapereaderwasusedtointerp
13、rettheinstructionswrittenonthetapeforthemachine/Together/allofthisrepresentedagiantstepforwardinthecontrolofmachinetools/However/therewereanumberofproblemswithNCatthispointinitsdevelopment/Amajorproblemwasthefragilityofthepunchedpapertapemedium/Itwascommonforthepapertapecontainingtheprogrammedinstru
14、ctionstobreakortearduringamachiningprocess/Thisproblemwasexacerbatedbythefactthateachsuccessivetimeapartwasproducedonamachinetool/thepapertapecarryingtheprogrammedinstructionshadtobererunthroughthereader/Ifitwasnecessarytoproduce100copiesofagivenpart/Ifitwasalsonecessarytorunthepapertapethroughthere
15、ader100separatetimes/Fragilepapertapessimplycouldnotwithstand3therigorsofashopfloorenvironmentandthiskindofrepeateduse/Thisledtothedevelopmentofaspecialmagneticplastictape/Whereasthepapertapecarriedtheprogrammedinstructionsasaseriesofholespunchedinthetape/theplastictapecarriedtheinstructionsasaserie
16、sofmagneticdots/Theplastictapewasmuchstrongerthanthepapertape/whichsolvedtheproblemoffrequenttearingandbreakage/However/itstilllefttwootherproblems/Themostimportantofthesewasthatitwasdifficultorimpossibletochangetheinstructionsenteredonthetape/Tomakeeventhemostminoradjustmentsinaprogramofinstruction
17、s/itwasnecessarytointerruptmachiningoperationsandmakeanewtape/Itwasalsostillnecessarytorunthetapethroughthereaderasmanytimesastherewerepartstobeproduced/fortunately/computertechnologybecamearealityandsoonsolvedtheofNCassociatedwithpunchedpaperandplastictape/Thedevelopmentofaconceptknownasdirectnumer
18、icalcontrol(DNC)solvedthepaperandplastictapeproblemsassociatedwithnumericalcontrolbyeliminatingtapeasthemediumforcarryingtheprogrammedinstructions/Indirectnumericalcontrol/machinetoolsaretied/viaadatatransmissionlink/toahostcomputer/Programsforoperatingthemachinetollsarestoredinthehostcomputerandfed
19、tothemachinetoolasneededviathedatatransmissionlinkage/Directnumericalcontrolrepresentedamajorstepforwardoverpunchedtapeandplastictape/However/itissubjecttothesamelimitationsasalltechnologiesthatdependonahostcomputer/Whenthehostcomputergoesdown/themachinetoolsalsoexperiencedowntime/Thisproblemledtoth
20、edevelopmentofcomputernumericalcontrol/Thedevelopmentofthemicroprocessorallowedforthedevelopmentofprogrammablelogiccontrollers(PLCs)andmicrocomputers/Thesetwotechnologiesallowedforthedevelopmentofcomputernumericalcontrol(CNC)/WithCNC/eachmachinetoolhasaPLCoramicrocomputerthatservesthesamepurpose/Thi
21、sallowsprogramstobeinputandstoredateachindividualmachinetool/Italsoallowsprogramstobedevelopedoff-lineanddownloadedattheindividualmachinetool/CNCsolvedtheproblemsassociatedwithdowntimeofthehostcomputer/butitintroducedanotherproblemknownasdatamanagement/Thesameprogrammightbeloadedontendifferentmicroc
22、omputerswithnocommunicationamongthem/Thisproblemisintheprocessofbeingsolvedbylocalareanetworksthatconnectmicrocomputersforbetterdatamanagement/Asapplicationthatnumericalcontrolisprocessedbeingextensivewithdeepeningdaybyday/CADandmanufacture(CAD/CAM)becomeahotissueofthe4mechanicalmanufacturingindustr
23、y/MakebyBeijingInstituteofAeronauticsCAXAthatHaierdevelopengineerrelyoncharacteristiconfunctioncomplete/easytolearnandusetheiruseextensively/CAXAisusedinnumericalcontrolmillingmachine/numericalcontrollathe/wirecuttingmachinetoolandmachiningcenter/etc/mainly/Thistextdiscussesapplicationonthemachining
24、centerofCAD/CAMsystem/itsessenceisthatCAXAmakestheengineerXPapplicationonmachiningcenter/Atthisstage/manyplantscommonlyusedtwo-dimensionaldesignsoftwarefor2Ddesignpartsoftheplans/andthecraftspersonnel/programmerat3DconceptdirectlytoGcodeoraptlanguageofNCprogramming/Thisapproachappliestosimplegraphic
25、processingcomponents/linearprocessing/turnaroundprocessinghardwareprocessingandpointspaces/Itsprogrammingisfastercodeconcise/Forcomplexgeometricshapes/jigassemblycomplex/especiallyfornon-Yuancamberprocessing/theprogrammingmethodwasverydifficult/Asatrajectoryofspacegeometricfigureandthemathematicalca
26、lculationofhandlinglarge/complexprocess/noteasilygraspandprogrammingprocess/theconstituentelementsoftheenvironmentcannotbeprocessedgeometricspacerelationsbetweeninspections/Aknifespacestargetcoordinatestothegeometricfiguretoinspectprocessing/precisionlow/notvisual/andtherefore/theneeddebuggingprocedures/occupancydigitalmachinehours/technicalpreparationsforthecyclelonger/
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