文献翻译--数控加工切削.doc

Figure9-12Tool-noseradiuscompensationallowsustoprogramthepart,notthetoolpath.Themathematicalcalculationsthatareneededtoprogramapartprofilewithanglesandradii,withouttheaidofcutterdiametercompensation,canbeveryinvolved.onaturningcenter.WhenwesettheXandZaxesofthetool,wecreateasquarepointonthetool.Mostofthetoolsweuseforturninghaveradii.Tocompensatefortheradii,weneedtouseTNRcompensation,whichsavesusfromhavingtomathematicallycalculatethecutterpath(seeFigure9-12).TNRcompensationalsoletsususethesameprogramforavarietyoftooltypes.WithTNRcompensationcapabilities,theinsertradiussizecanbeignoredandthepartprofilecanbeprogrammed.Theexactsizeofthecuttingtooltobeusedisenteredintotheoffsetfile,andwhentheoffsetiscalled,thetoolpathwillautomaticallybeoffsetbythetoolradius.Tool-noseradiuscompensationcanbetotherightorleftofthepartprofile.Todeterminewhichoffsetyouneed,imagineyourselfwalkingbehindthecuttingtool.Doyouwantthetooltotheleftoftheprogrammedpathortotheright(seeFigure9-13)?Figure9-13Tool-nosecompensation.CompensationdirectioniscontrolledbyaG-code.Whenacompensationtotheleftisdesired,aG41isused.Whenacompensationtotherightisneeded,aG42isused.Whenusingthesecuttercompensationcodes,youneedtospecifyhowmuchthecontrolleristooffset.Thesizeoftheradiusisplacedinthenoseradiusoffsettable,whichistypicallylocatedadjacenttothetoolfileunderthetoolnumberbeingused.Tool-noseradiusinformationcanbedeterminedfromcatalogsortheinsertpackage.Otherinformationneededtoinsurepropercompensationisthetoolnosedirectionvector.Thetooltiporimaginarytooltipofturningtoolshasaspecificlocationordirectionfromthecenterofthetool-noseradius.Thetoolnosevectortellsthecontrolwhichdirectionitmustcompensateforindividualtypesoftools.Standardtool-nosedirectionvectorsareshowninFigure14.Thedirectionvectornumberisusuallyplacedinthesametooloffsettableastheradiusvalue.Figure9-14Tool-noseradiusdirectionvectors.Toinvokecompensation,theprogrammerwillhavetomakeamachinemove(rampon).Thismoveallowsthecontroltoevaluateitspresentpositionandmakethenecessaryadjustmentfromtool-edgepositioningtotool-noseradiuspositioning.Thisadjustmentmovemustbegreaterthantheradiusvalueofthetool.Tocancelthecuttercompensationandreturntocutter-edgeprogramming,theprogrammermustmakealinearmove(rampoff)toinvokeacuttercompensationcancellation(G40).Figure9-15illustratesatypicalpartthatusestool-noseradiuscompensation.Theprogramforthepartfollowsthefigure.N0001G90G20；N0005G40；N0010T0101；N0015G92X5.800Z10.250；N0020G96S400M03；N0025GOOG42Xl.30Z.100；(RapidpositionramponmoveandTNRcompensationtotheright)N0035GOOX.375；(Profileofthepart)N0045G01Z0.0F.01；(Profileofthepart)N0050G01X.500Z-.0625；(Profileofthepart)N0055G01Z-1.00；(Profileofthepart)N0060G02Xl.00Z-1.251.25K0.0；(Profileofthepart)N0065G01X1.25；(Profileofthepart)N0070G40G00X2.0Z2.0；(TNRcompensationcancelandrapidpositionrampoffmove)N0075G28；N0080T0100；N0085M30；Figure9-15Programthatutilizestool-noseradiuscompensation.CANNEDCYCLESFORTURNINGCENTERSCannedcycles(fixed)cyclesareusedtosimplifytheprogrammingofrepetitiveturningoperations,suchasroughturning,threading,andgrooving.Cannedcyclesaresetsofpreprogrammedinstructionsthateliminatetheneedformanylinesofprogramming.Programmingasimplepartwithouttheuseofacannedcyclecantakeuptofourorfivetimesthenumberoflinesneededforapartprogrammedwithcannedcycles.Thinkofthelinesthatareneededtoproduceathread:(1)positiontheXandZaxestothepropercoordinateswitharapidtraversemove(G00),(2)positionthetoolfortheproperleadangle,(3)feedthetoolacross,(4)rapidpositionthetoolbacktotheclearanceplan,(5)feedthetoolacross.Thatisonlytwothreadingpasses.Withacannedthreadingcycle,athreadcanbedonewithonelineofprogramming.Standardcannedcycles,orfixedcycles,arecommontomostCNCmachines.SeeFigure9-4foragenerallistofthemostcommonlyusedcannedcyclesforturningcenters.ROUGHINGORTURNINGCYCLE(G71)TheG71automaticallytakesroughingpassestoturndownaworkpiecetoaspecificdiameterataspecifieddepthofcut.TheG71cyclereadsaspecifiednumberofblockstodeterminethepartprofileanddetermineseachpass,thedepthofcutforeachpass,andthenumberofrepeatpassesforthecycle.CuttingisaccomplishedthroughparallelmovesofthetoolintheZaxisdirection.Acertainprocedureneedstobefollowedwhenusingcannedcycles.Inthefirstprocedure,thetoolneedstobepositionedtotheroughstockboundaries.Thisprocedurehasatwo-foldpurpose:ittellsthecontrolhowbigthestockis,anditcreatesaZclearancepositionthatthetoolrapidsbacktooneachpass.TheG71usesletterstogivethecontrollerinformationonthepartprofile,theamountofstockwearegoingtoleaveforfinishing,thedepthofcut,andthefeedrate.AG71roughingcyclecommandfollows.N0010G71P40Q85U.03W.010D750F.012；G71istheroughingcyclecall.P40istheblockorlinenumberthatdesignatesthestartofthepartprofile.Q85istheblockorlinenumberthatdesignatestheendofthepartprofile.U.03tellsthecontrollerthatwewanttoleave.03ofaninchstockontheXaxisoftheprofileforfinishing.W.O1tellsthecontrollerthatwewanttoleave.01ofaninchstockontheZaxisoftheprofileforfinishing.D750tellsthecontrollerwewanttotake.0750ofaninchperpasspersidedepthofcut.Noticethatthedecimalpointwasleftoff.Nodecimalpointinputispossiblefordepthofcut.WhentheDiscommandedthecontrollerreadsfromtherightanddecideswhatthedepthofcutwillbe.Eachnumberineachdecimalpositiongetsavalue.Ifwewantedtotake.0500depthofcutperside,wewouldwriteitasD500.Thefirstzerofromtherighthas0tenthsofathousandthsvalue.Thenextzerofromtherighthas0thousandthsofaninchvalue.The5inthethirdpositionfromtherighthas5ten-tho