数控技术专业英语(第2版)课件 Unit 1

UnitOneDialogueTextSupplementaryReadingDialogueTopicalIntroduction:TomandMaryhavenowjustfinishedaclassgivenbyProfessorSmithontheworkingsofthemachinetools.Yet,theystillhavesomequestions,andso,theywalkovertoProf.Smith.

下一页返回DialogueTom:(toProf.Smith)Excuseme,sir,I’mTom,oneofyourstudentsinthisclass.CouldIaskyousomequestions?Smith:(toTom)Whynot?Comeon,then

Tom:Whydowenamethesemachinesnumericalcontrolmachines?

Smith:Agoodquestion,boy.Youknow,uh-hm….,NC,ornumericalcontrol,actuallyreferstothecontrolofamachinetooloranyotherprocessingmachinesbyusingaseriesofmathematicalinformation,ornumericaldata.Itmeanstheworkofmachinesiscontrolledbyanumericalcontrolprogram.

下一页上一页返回DialogueMary:Oh,Prof.Smith,theideaisniceenough.Butwhatistheadvantageofnumericalcontrolmachiningoverthehandcontrol?Isn’tourhandmoresensibleorreliablethantheprogrammeddata?

Smith:Insomeways,yes.Agoodexampleissomefineworks,likeajadebox,butthequalitiesofhand-madeproductsmaynotbeconsistentorstable.Whatismoreimportant,NChasprovedtobemuchmoreadvantageousinoveralloperation.Mary:Butwhatdoyoumeanbyoveralloperation?下一页上一页返回DialogueSmith:Uh-huh,byitwemeanthegeneralindustrialproductionpractice.Forexample,NCshouldbeadoptedwheneverthereissimilarrawmaterialandworkpartsareproducedinvarioussizesandcomplexshapes.ThoseproductionshopsthatmayhavefrequentchangeoverswillsurelybenefitfromNCprograms.

Tom:Thankyou,Prof.Smith,butIhaveanotherquestion.HowcanweuseNCtogetmoresatisfactoryresultsintherealproduction?

下一页上一页返回DialogueSmith:It’sbettertouseNCtoolstogetherwithothertechnicaladvances,suchasprogrammedoptimizationofcuttingspeedsandfeeds,workpositioning,toolselection,andchipdisposal.Tom&Mary:ThankyouProf.Smith,NCsoundsreallypromisingfromwhatwesay.

上一页返回TextTheHistoryofCNCandNCDevelopment

下一页返回Text

NumericalControl(NC)isanymachiningprocessinwhichtheoperationsareexecutedautomaticallyinsequencesasspecifiedbytheprogramthatcontainstheinformationforthetoolmovements.TheNCconceptwasproposedinthelate1940sbyJohnParsonsofTraverseCity,Michigan.Parsonsrecommendedamethodofautomaticmachinecontrolthatwouldguideamillingcuttertoproducea“thru-axiscurve”inordertogeneratesmoothprofilesonworkpieces.

In1949,TheU.S.AirForceawardedParsonsacontracttodevelopanewtypeofmachinetoolthatwouldbeabletospeedupproductionmethods.

下一页上一页返回TextParsonscommissionedtheMassachusettsInstituteofTechnology(M.I.T)todevelopapracticalimplementationofhisconcept1.ScientistsandengineersatM.I.Tbuiltacontrolsystemforatwo-axismillingmachinethatusedaperforatedpapertapeastheinputmedia.Inashortperiodoftime,allmajormachinetoolmanufacturerswereproducingsomemachineswithNC,butitwasnotuntilthelate1970sthatcomputer-basedNCbecamewidelyused.NCmaturedasanautomationtechnologywheninexpensiveandpowerfulmicroprocessorsreplacedhard-wirelogic-makingcomputer-basedNCsystems.

下一页上一页返回Text下一页上一页返回TextWhenNumericalControlisperformedundercomputersupervision,itiscalledComputerNumericalControl(CNC).ComputersarethecontrolunitsofCNCmachines,theyarebuiltinorlinkedtothemachinesviacommunicationschannels.Whenaprogrammerinputsomeinformationintheprogrambytapeandsoon,thecomputercalculatesallnecessarydatatogetthejobdone.

OnthefirstNumericallyControlled(NC)machineswerecontrolledbytape,andbecauseofthat,theNCsystemswereknownastape-controlledmachines2.下一页上一页返回TextTheywereabletocontrolasingleoperationenteredintothemachinebypunchedormagnetictape.Therewasnopossibilityofeditingtheprogramonthemachine.Tochangetheprogram,anewtapehadtobemade.

Today’ssystemshavecomputerstocontroldata;theyarecalledComputerNumericallyControlled(CNC)machines.ForbothNCandCNCsystems,workprinciplesarethesame.Onlythewayinwhichtheexecutioniscontrolledisdifferent.Normally,newsystemsarefaster,morepowerful,andmoreversatile3.

上一页返回Notes

1.ParsonscommissionedtheMITtodevelopapracticalimplementationofhisconcept.帕森委托麻省理工学院开发他设想中的实际机器。todevelopa…作目的状语。

返回Notes2.Onthefirstnumericallycontrolled(NC)machines,numericaldatawascontrolledbytapeandbecauseofthat,theNCsystemwereknownastape-controlledmachine.that指代上一句onthefirstNumericallycontrolled(NC)machines,numericaldatawascontrolledbytape,可译为：在最初的NC机床上，其数据由磁带提供及控制，因此这种数控系统被称为磁盘控制机。

返回Notes3.Normally,newsystemsarefaster,morepowerful,andmoreversatile.normally,-ly结尾的副词单独作状语放于句首时，通常作评注状语。本句可译为：“一般说来，这种新系统加工速度更快，功率更大，功能更强。

返回SupplementaryReadingTheApplicationsofNC/CNC

Sinceitsintroduction,NCtechnologyhasfoundmanyapplications,includinglathesandturningcenters,millingmachinesandmachiningcenters,punches,electricaldischargemachines(EDM),flamecutters,grinders,andtestingandinspectionequipment.ThemostcomplexCNCmachinetoolsaretheturningcenter,showninFig.1-1(Amodemturningcenterwithaten-stationturretthatacceptsquick-changetools.

EachtoolcanbepositionedinSecondswiththepressofabutton).下一页返回Fig.1-1返回Fig.1-1Amodernturningcenterwithaten–stationturretthatacceptsquick-changetools

SupplementaryReadingAndthemachiningcentershowninFig.1-2(Verticalmachiningcenter,thetoolmagazineisontheleftofthemachine.Thecontrolpanelontherightcanbeswiveledbytheoperator)andFig.1-3(Horizontalmachiningcenter,equippedwithanautomatictoolchanger.Toolmagazinescanstore200cuttingtools).

下一页上一页返回Fig.1-2返回Fig.1-2Avertical-spindlemachinecenter

Fig.1-3返回Fig.1-3Ahorizontal-spindlemachinecenter

SupplementaryReadingWhenpreparingaprogramforaparticularoperation,theprogrammermustselectallcuttingdatausingrecommendationsforconventionalmachining.Thisincludesproperselectionofcuttingspeeds,federate,toolsandtoolgeometry,andsoon.Whentheprogrammerhaschosenallofthenecessaryinformationproperly,theoperatorloadstheprogramintothemachineandpressesabuttontostartthecuttingcycle.TheCNCmachinemovesautomaticallyfromonemachiningoperationtoano