组合机床论文中英文资料外文翻译文献文档格式.docx

组合机床论文中英文资料外文翻译文献文档格式.docx

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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（PC