《数控技术双语》习题参考答案Word文档格式.docx
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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