组合机床外文翻译文献.docx
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组合机床外文翻译文献.docx
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组合机床外文翻译文献
中英文资料外文翻译
TRANSFERANDUNITMACHINE
Whilethespecificintentionandapplicationfortransferandunitmachinevaryfromonemachinetypetoanother,allformsoftransferandunitmachinehavecommonbenefits.HerearebutafewofthemoreimportantbenefitsofferedbyTRANSFERANDUNITMACHINEequipment.
Thefirstbenefitofferedbyallformsoftransferandunitmachineisimprovedautomation.Theoperatorinterventionrelatedtoproducingworkpiecescanbereducedoreliminated.Manytransferandunitmachinecanrununattendedduringtheirentiremachiningcycle,freeingtheoperatortodoothertasks.Thisgivesthetransferandunitmachineuserseveralsidebenefitsincludingreducedoperatorfatigue,fewermistakescausedbyhumanerror,andconsistentandpredictablemachiningtimeforeachworkpiece.Sincethemachinewillberunningunderprogramcontrol,theskilllevelrequiredofthetransferandunitmachineoperator(relatedtobasicmachiningpractice)isalsoreducedascomparedtoamachinistproducingworkpieceswithconventionalmachinetools.
Thesecondmajorbenefitoftransferandunitmachinetechnologyisconsistentandaccurateworkpieces.Today'stransferandunitmachinesboastalmostunbelievableaccuracyandrepeatabilityspecifications.Thismeansthatonceaprogramisverified,two,ten,oronethousandidenticalworkpiecescanbeeasilyproducedwithprecisionandconsistency.
rdbenefitofferedbymostformsoftransferandunitmachinetoolsisflexibility.Sincethesemachinesarerunfromprograms,runningadifferentworkpieceisalmostaseasyasloadingadifferentprogram.Onceaprogramhasbeenverifiedandexecutedforoneproductionrun,itcanbeeasilyrecalledthenexttimetheworkpieceistoberun.Thisleadstoyetanotherbenefit,fastchangeover.Sincethesemachinesareveryeasytosetupandrun,andsinceprogramscanbeeasilyloaded,theyallowveryshortsetuptime.Thisisimperativewithtoday'sjust-in-time(JIT)productrequirements.
Motioncontrol-theheartoftransferandunitmachine
Themostbasicfunctionofanytransferandunitmachineisautomatic,precise,andconsistentmotioncontrol.Ratherthanapplyingcompletelymechanicaldevicestocausemotionasisrequiredonmostconventionalmachinetools,transferandunitmachinesallowmotioncontrolinarevolutionarymanner2.Allformsoftransferandunitmachineequipmenthavetwoormoredirectionsofmotion,calledaxes.Theseaxescanbepreciselyandautomaticallypositionedalongtheirlengthsoftravel.Thetwomostcommonaxistypesarelinear(drivenalongastraightpath)androtary(drivenalongacircularpath).
Insteadofcausingmotionbyturningcranksandhandwheelsasisrequiredonconventionalmachinetools,transferandunitmachinesallowmotionstobecommandedthroughprogrammedcommands.Generallyspeaking,themotiontype(rapid,linear,andcircular),theaxestomove,theamountofmotionandthemotionrate(feedrate)areprogrammablewithalmostalltransferandunitmachinetools.
Atransferandunitmachinecommandexecutedwithinthecontroltellsthedrivemotortorotateaprecisenumberoftimes.Therotationofthedrivemotorinturnrotatestheballscrew.Andtheballscrewdrivesthelinearaxis(slide).Afeedbackdevice(linearscale)ontheslideallowsthecontroltoconfirmthatthecommandednumberofrotationshastakenplace3.Refertofig.1.
Fig.1
Thougharathercrudeanalogy,thesamebasiclinearmotioncanbefoundonacommontablevise.Asyourotatethevisecrank,yourotatealeadscrewthat,inturn,drivesthemovablejawonthevise.Bycomparison,alinearaxisonatransferandunitmachinemachinetoolisextremelyprecise.Thenumberofrevolutionsoftheaxisdrivemotorpreciselycontrolstheamountoflinearmotionalongtheaxis.
Howaxismotioniscommanded-understandingcoordinatesystems
Itwouldbeinfeasibleforthetransferandunitmachineusertocauseaxismotionbytryingtotelleachaxisdrivemotorhowmanytimestorotateinordertocommandagivenlinearmotionamount4.(Thiswouldbelikehavingtofigureouthowmanyturnsofthehandleonatablevisewillcausethemovablejawtomoveexactlyoneinch!
)Instead,alltransferandunitmachinecontrolsallowaxismotiontobecommandedinamuchsimplerandmorelogicalwaybyutilizingsomeformofcoordinatesystem.Thetwomostpopularcoordinatesystemsusedwithtransferandunitmachinesaretherectangularcoordinatesystemandthepolarcoordinatesystem.Byfar,themorepopularofthesetwoistherectangularcoordinatesystem.
Theprogramzeropointestablishesthepointofreferenceformotioncommandsinatransferandunitmachineprogram.Thisallowstheprogrammertospecifymovementsfromacommonlocation.Ifprogramzeroischosenwisely,usuallycoordinatesneededfortheprogramcanbetakendirectlyfromtheprint.
Withthistechnique,iftheprogrammerwishesthetooltobesenttoapositiononeinchtotherightoftheprogramzeropoint,X1.0iscommanded.Iftheprogrammerwishesthetooltomovetoapositiononeinchabovetheprogramzeropoint,Y1.0iscommanded.Thecontrolwillautomaticallydeterminehowmanytimestorotateeachaxisdrivemotorandballscrewtomaketheaxisreachthecommandeddestinationpoint.Thisletstheprogrammercommandaxismotioninaverylogicalmanner.Refertofig.2,3.
Fig.2
Fig.3
Alldiscussionstothispointassumethattheabsolutemodeofprogrammingisused6.ThemostcommontransferandunitmachinewordusedtodesignatetheabsolutemodeisG90.Intheabsolutemode,theendpointsforallmotionswillbespecifiedfromtheprogramzeropoint.Forbeginners,thisisusuallythebestandeasiestmethodofspecifyingendpointsformotioncommands.However,thereisanotherwayofspecifyingendpointsforaxismotion.
Intheincrementalmode(commonlyspecifiedbyG91),endpointsformotionsarespecifiedfromthetool'scurrentposition,notfromprogramzero.Withthismethodofcommandingmotion,theprogrammermustalwaysbeasking"HowfarshouldImovethetool?
"Whiletherearetimeswhentheincrementalmodecanbeveryhelpful,generallyspeaking,thisisthemorecumbersomeanddifficultmethodofspecifyingmotionandbeginnersshouldconcentrateonusingtheabsolutemode.
Becarefulwhenmakingmotioncommands.Beginnershavethetendencytothinkincrementally.Ifworkingintheabsolutemode(asbeginnersshould),theprogrammershouldalwaysbeasking"Towhatpositionshouldthetoolbemoved?
"Thispositionisrelativetoprogramzero,NOTfromthetoolscurrentposition.
Asidefrommakingitveryeasytodeterminethecurrentpositionforanycommand,anotherbenefitofworkingintheabsolutemodehastodowithmistakesmadeduringmotioncommands.Intheabsolutemode,ifamotionmistakeismadeinonecommandoftheprogram,onlyonemovementwillbeincorrect.Ontheotherhand,ifamistakeismadeduringincrementalmovements,allmotionsfromthepointofthemistakewillalsobeincorrect.
Assigningprogramzero
Keepinmindthatthetransferandunitmachinecontrolmustbetoldthelocationoftheprogramzeropointbyonemeansoranother.Howthisisdonevariesdramaticallyfromonetransferandunitmachineandcontroltoanother8.One(older)methodistoassignprogramzerointheprogram.Withthismethod,theprogrammertellsthecontrolhowfaritisfromtheprogramzeropointtothestartingpositionofthemachine.ThisiscommonlydonewithaG92(orG50)commandatleastatthebeginningoftheprogramandpossiblyatthebeginningofeachtool.
Another,newerandbetterwaytoassignprogramzeroisthroughsomeformofoffset.Refertofig.4.Commonlymachiningcentercontrolmanufacturerscalloffsetsusedtoassignprogramzerofixtureoffsets.Turningcentermanufacturerscommonlycalloffsetsusedtoassignprogramzeroforeachtoolgeometryoffsets.
Fig.4
Flexiblemanufacturingcells
Aflexiblemanufacturingcell(FMC)canbeconsideredasaflexiblemanufacturingsubsystem.ThefollowingdifferencesexistbetweentheFMCandtheFMS:
1.AnFMCisnotunderthedirectcontrolofthe
centralcomputer.Instead,instructionsfromthecentral
computerarepassedtothecellcontroller.
2.Thecellislimitedinthenumberofpartfamiliesit
canmanufacture.
ThefollowingelementsarenormallyfoundinanFMC:
•Cellcontroller
•Programmablelogiccontroller(PLC)
•Morethanonemachinetool
•Amaterialshandlingdevice(robotorpallet)
TheFMCexecutesfixedmachiningoperationswithpartsflowingsequentiallybetweenoperations.
Highspeedmachining
ThetermHighSpeedMachining(HSM)commonlyreferstoendmillingathighrotationalspeedsandhighsurfacefeeds.Forinstance,theroutingofpocketsinaluminumairframesectionswithaveryhighmaterialremovalrate1.Overthepast60years,HSMhasbeenappliedtoawiderangeofmetallicandnon-metallicworkpiecematerials,includingtheproductionofcomponentswithspecificsurfacetopographyrequirementsandmachiningofmaterialswithhardnessof50HRCandabove.Withmoststeelcomponentshardenedtoapproximately32-42HRC,machiningoptionscurrentlyinclude:
Roughmachiningandsemi-finishingofthematerialinitssoft(annealed)conditionheattreatmenttoachievethefinalrequiredhardness=63HRCmachiningofelectrodesandElectricalDischargeMachining(EDM)ofspecificpartsofdiesandmoulds(specificallysmallradiianddeepcavitieswithlimitedaccessibilityformetalcuttingtools)finishingandsuper-finishingofcylindrical/flat/cavitysurfaceswithappropriatecementedcarbide,cermet,solidcarbide,mixedceramicorpolycrystallinecubicboronnitride(PCBN)
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