《数控技术双语》习题参考答案.docx

《数控技术双语》习题参考答案.docx

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《数控技术双语》习题参考答案

《数控技术（双语）》习题参考答案

Chapter1IntroductionofCNC

1.1NarratetheconceptofNC.

Numericalcontrol（NC）isaformofprogrammableautomationinwhichthemechanicalactionsofamachinetoolorotherequipmentarecontrolledbyaprogramcontainingcodedalphanumericdata.

1.2NarratetheconceptofCNC.

ACNCmachineisanNCmachinewiththeaddedfeatureofanonboardcomputer.TheonboardcomputerisoftenreferredtoasthemachinecontrolunitorMCU.ControlunitsforNCmachinesareusuallyhardwired,whichmeansthatallmachinefunctionsarecontrolledbythephysicalelectronicelementsthatarebuiltintothecontroller.

1.3WhatarethecomponentsofCNCmachinetool,andthefunctionofeachcomponent?

StructureofCNCmachinetool

CNCmachineiscomposedthefollowingparts.

（1）CNCdevice

TheCNCdeviceisthekerneloftheCNCsystem.Itsfunctionistohandletheinputpartmachiningprogramoroperationcommand,thenoutputcontrolcommandtotheappropriateexecutivepartsandfinishtheworkwhichthepartsmachiningprogramandoperationneed.

（2）ServoUnit,drivedeviceandmeasuredevice

Servounitanddrivedeviceincludespindleservodrivedevice,spindlemotor,feedservodrivedeviceandfeedmotor.Measuredevicemeanspositionandspeedmeasuredevice,itisanecessarydevicetofinishthespindlecontrol,closed-loopforthefeedspeedandforthefeedposition.

（3）Controlpanel

Controlpanel,calledoperationpanel,isatoolusedformutualinformationbetweentheoperatorandtheCNCmachine.

（4）Controlmediumandprograminputandoutputequipment

Thecontrolmediumisanagenttorecordthepartmachiningprogramanditisalsothemediumtosetupcontractionbetweenmanandmachine.PrograminputandoutputequipmentarethedevicesbywhichtheinformationexchangecanbedonebetweentheCNCsystemandexternalequipment.ItseffectistoinputthepartmachiningprogramrecordedonthecontrolmediumintotheCNCsystemandtostoreorrecordthedebuggedpartmachiningprogramontheappropriatemediumwiththeoutputdevice.

（5）Machinebody

TheobjectofCNCsystemistheexecutiveparttofulfillthemachiningparts.Itiscomposedofthemainmotionparts,feedmotionparts,bearingrackandspecialdevice,automaticplatformchangesystem,automatictoolchangersystemandaccessorydevice.

1.4WhatisthePoint-to-pointcontrol,Contouringcontrol?

Point-to-pointsystem,alsocalledPositingcontrolsystems,movestheworktabletoaprogrammedlocationwithoutregardforthepathtakentogettothelocation.

ThecontouringfacilityenablesaCNCmachinetofollowanypathatanyprescribedfeed-rate.Thecontouringcontrolsystem,alsocalledcontinuouspathcontrolsystems,managesthesimultaneousmotionofthecuttingtoolintwo,three,four,orfiveaxes（thefourthandfifthaxesareangularorientations）byinterpolatingtheproperpathbetweenprescribedpoints.

1.5Whatistheopen-loopcontrol,Half-closed-loopcontrolandClosed-loopcontrol?

Open-loopsystemshavenoaccesstotherealtimedataabouttheperformanceofthesystemandthereforenoimmediatecorrectiveactioncanbetakenincaseofsystemdisturbance.

Asemi-closed-loopcontrolCNCsystemusesfeedbackmeasurementstoensurethattheworktableismovedtothedesiredposition.Itischaracterizedasasystemthattheindirectfeedbackmonitorstheoutputofservomotor.

Inacloseloopsystem,feedbackdevicescloselymonitortheoutputandanydisturbancewillbecorrectedinthefirstinstance.

1.6WhataretheadvantagesanddisadvantagesofCNC?

CNCopensupnewpossibilitiesandadvantagesnotofferedbyolderNCmachines.

（1）Reductioninthehardwarenecessarytoaddamachinefunction.NewfunctionscanbeprogrammedintotheMCUassoftware.

（2）TheCNCprogramcanbewritten,stored,andexecuteddirectlyattheCNCmachine.

（3）AnyportionofanenteredCNCprogramcanbeplayedbackandeditedatwill.Toolmotionscanbeelectronicallydisplayeduponplayback.

（4）ManydifferentCNCprogramscanbestoredintheMCU.

（5）SeveralCNCmachinescanbelinkedtogethertoamaincomputer.ProgramswrittenviathemaincomputercanbedownloadedtoanyCNCmachineinthenetwork.ThisisknownasdirectnumericalcontrolorDNC.

（6）SeveralDNCsystemscanalsobenetworkedtoformalargedistributivenumericalcontrolsystem.

（7）TheCNCprogramcanbeinputfromflashorfloppydisksordownloadedfromlocalareanetworks.

CNCmachinescandramaticallyboostproductivity.TheCNCmanager,however,canonlyensuresuchgainsbyfirstaddressingseveralcriticalissues,suchasthefollowing:

（1）SufficientcapitalmustbeallocatedforpurchasingqualityCNCequipment.

（2）CNCequipmentmustbemaintainedonaregularbasisbyobtainingafull-servicecontractorbyhiringanin-housetechnician.

（3）Personnelmust