外文翻译--计算机辅助数控编程应用于非典型零件的加工.doc

COMPUTER-AIDEDCNCPROGRAMMINGFORTHEMACHININGOFNON-TYPICALPARTSGrzegorzNikielGrzegorzNIKIEL,Ph.D.,Eng.,UniversityofBielsko-Biaa,DepartmentofManufacturingTechnologyandAutomation,43-309Bielsko-Biaa,ul.Willowa2,gnikielath.bielsko.pl1.IntroductionManymanufacturingfirms,especiallymediumandsmall,hastosolveproblemofproductiondevelopmentandsearchofnewcustomers.Inmanycasesthisleadstotheassortmentenlargingofalreadymanufacturedproducts.Oftenthisisjoinedwithimplementationofthenewmanufacturingprocesses.InconditionsofmarketcompetitionitdemandshighflexibilitywhichisoftengotinwayreplacingofconventionalmanufacturingresourcesbythemodernCNCtoolmachines1.Thisisessentialsconditionformoreefficientdevelopment,higherqualityandfasteradoptiontonewrequirements2.FormaintenanceofthelowcostsofmanufacturingforproductionofsmallandmediumbatchesveryoftentheGroupTechnologyisapplied3.Withhelpofgroupingofthemanufacturedcomponentsintofamiliesmoreefficientthemachines,devices,workersareused.IntheprocessesplanningonefrommostimportanttasksistheCNCmachinetoolprogramming4,5.VeryoftentheCAD/CAMsystemsareusedfromreasontheirpossibilityofflexibleprogramming.Inthecaseoftypicalcomponentssuchapproachthepositiveresultsgives,thoughitdemandsanefficientco-operationsbetweenconstructorsandtechnologist.Sometimesfromdifferentreasonsitisimpossible,especiallywhentheGroupTechnologyisapplied.Usuallythepartprogramsformachiningofsinglecomponentsarecreated,butthemodernCNCcontrollersoffersomemethodsofprogramming,whichtomachiningofsomesimilarcomponentscanbeused.Suchmethodsare:1.Cycles6.Thecyclesaredesignformachiningoftypicalsurfaces(theholes,threads,slotsetc.).Usuallyaparametricdescriptionofmachinedsurfacesisappliedwhichenabletheeasyandfastchangesoftheirgeometry.Unfortunatelytheybecharacterizedbysmallflexibilityandsmallinfluenceontostrategyofmachining,dependentonlyfromtheparametersofcycle.InthemoderncontrollersitpermitontoaWorkshopOrientedProgramming(WOP),grammingdirectlybytheoperators,oftenaidedbyadialogprogramming(sometimesaconversationalprogrammingcalled).Thereforethisisrelativesimpleprogrammingmethod,veryoftenusedinindustrialpractice.2.Parametricprogramming5,6.Atypicalpartprogramisexecutedfrombeginningtoendinonerun.Inparametricprogrammingtheexecutionofpartprogramcanrunintodifferentway(e.g.byconditionalinstructionIF.THEN.use).Inaddition,amultiplerepetitionofthepartprogramfragmentisaccessible(REPEATloop,WHILEloopetc.).Furthermore,thearithmeticalfunctionsandotheradvancedfunctionsarepossible.Theaxispositions,feedandspeedfunctions,etc.canbespecifiedbyaparametricexpressions(byR-parametersuse).Intothiswayitwasbeenpossibletocreateownmachiningcyclesalso.Thisapproachdemandshighskillsofprogrammingandisverylabour-consumingalso.Exactverificationoftheprogramisnecessary,inthisitsimmunityinthedangeroussituations(e.g.joinedwithapplicationofincorrectvalueoftheinputparameters).Thereforeinviewofabovementioneddefectsitisinfrequentlyusedinindustrialpractice.3.Programmingbasedonthefreelydefinedcontours.ThetaskdependsondefiningofmachinedcontouranditsautomaticconversiontotheCNCcodes.Iftheautomaticcutterradiuscompensation(theG41andG42functions)isnotusedthenadditionallyaequidistanthastobegenerated.Thissub-taskiseasytorealizationifmentionedcontourisrepresentedinaCADsystemwithhelpoftheOffsetfunction.Secondsub-taskoftenisrealizedinwayofexportofgraphicformofthetoolpathtothetypicalformatsofdataexchange(DXF,HPGLetc.).Innextstepbythesuitablepostprocessorsuse(forexamplethesolutiongivenin7)conversionoftoolpathontotheCNCcodesisperformed.Frompracticalregardsthisapproachingeneralityforthesimpleoperationsisapplied,e.g.alasercutting,awaterjetcuttingetc.Asolutionintegratingbothsub-tasksinoneapplicationprogramareappliedalsotheAutoCUTisthebestexample8.Inpracticethissolutionisnotappliedtoooftenalthoughitpossessesmanyadvantages.IntheconditionsofsmallbatchproductionaprocessplanningtotheCNCprogrammingisoftenrestricted9.InthissituationlargemeaninghasintegrationoftheCAD/CAMsystemswithomissionofCAPPstage.TheFeaturesideaisthenaeffectivemethodofdataexchange10,11,12.WhentheGroupTechnologyisused,aftersupplementbyappropriatedatabasesandknowledgebases,itcanbebestsolutionforproductionoftypicalelements13,14.Incaseofnon-typicalpartssuchapproachgenerallyisineffective.MainlyinviewofthewidelyappliedmethodsofFeaturesrecognizingwhichlimitnumberoftheFeaturetypes10,12.MaybeinfutureasolutionwillbringintegrationofCAD/CAM/CNCsystemsbasedontheSTEP-NCstandards(ISO14649,ISO10303:238)15,16whichwillreplacetraditionallyappliedCNCprogrammingwithG-codesontothingoftheneutralformatofdataexchange.2.AnalysisoftheexamplesPresentedbelowexamplesofthegroupCNCmachiningareafragmentofproductionprogramfromthesmallfirm.Generallythiscomponentshavenon-typicalshapes,theyaremanufacturedfromhardmaterials(e.g.austeniticstainlesssteel),usuallyneededthespecialjigsandfixtures,intheconditionsofsmallbatchproduction.Theplanningprocessesinthiscasedemandaparticipationoftechnologistswithlargeexperience.AspecificcharacterofaccessibletoolmachinesfordefiningofthemethodofCNCprogrammingshouldtoconsideralso.Afterexecutionofdetailedanalysisontosubjectofthediscussedmethodsthefollowingconclusionswereformulated:Themachinedshapesexcludeapplyingofthestandardcycles.Mostoftheprogramsisdesignforthecomplicatedprofilesmachining.Fromheredescriptionoftheseprofilesislargestproblem.Moreover,machiningofthecomponentsisperformedonthedifferenttoolmachines,equippedindifferentcontroller.Formostofmachinedcomponentstheexactdrawingdocumentationisnotmade.Inaproductionorderthegeneraldrawingsareincluded,oftendescribedbyparametricdimensions.Thencurrentvaluesofthisparametersaregivenalso.Shortseriesandlargevarietyofthecomponentsdemandsfastmodifyingofcurrentproductionprogram.FastCNCprogrammingandtheprogramsimplementationisnecessary,bestdirectlyattoolmachine(WOP).Oftentheoperatorsoftoolmachinespossesslargeknowledgeandexperienceintheareaofmanufacturingtechnology,sufficientforpreparationofsimpleprogram(inrangeofthetechnology).Fastpreparationofthetoolpathislimitationonly.Generalconclusionissuch,thatinpresentedcaseuseoftheuniversalCAD/CAMsystemsforCNCprogrammingisverydifficult.Moreover,itjoinswithhighcostsofshoppingandtrainingsfortheworkers.Lowflexibilityofthismethodisexpectedalso,especiallytimeofprogrammingcanbeagreatproblem.Inthissituationaparametricprogrammingasthebestsolutionwasconsidered.But,asitwasshewontheexamples,theparametricprogrammingcanberealizedindifferentway.2.1.ExampleIthegroovedrollersfinishmachiningFinishmachiningofthegroovedrollersfamilywassubjectofresearch(Fig.1).Basicchangingdimensions