JournalofMaterialsProcessingTechnology139(2003)472475ResearchintotheengineeringapplicationofreverseengineeringtechnologyYuZhangCIMSApplicationandResearchCenter,SchoolofMechanicalandAutomationEngineering,KunmingUniversityofScienceandTechnology,Kunming650093,Yunnan,PRChinaAbstractBasedonpreviousresearchonreverseengineering(RE)technology,theengineeringapplicationofREisexploredinthispaper.TheapplicationenvironmentofREisbuiltwithcoordinatemeasurementmachine(CMM)andCAD/CAMsoftware.Takingacoredieoftheinletofadieselengineasanexample,thispaperdescribestheprocessesofRE,fromobjectdigitization,CADmodelreconstructiontoNCmachining.Measurementdataareacquiredbyscanningthephysicalobjectusingathree-dimensionalCMM.Throughprocessingofmeasurementdata,theauthorssucceedincreatingaCADmodelofthedieandmachiningthedie,gainingagoodresult.2003ElsevierScienceB.V.Allrightsreserved.Keywords:Reverseengineering；Productdevelopment；CAD/CAM1.IntroductionNowadays,competitivepressurehasreachedthepoint,whererapidproductdesignandoptimizationneedtobeembracedwithintheproductdevelopmentcycle.Ashortlead-timeinproductdevelopmentisstronglydemandedtosatisfyneeds,resultingfromtheglobalizationofmanufac-turingactivitiesandthechangesinmarketrequirements.Inengineeringareassuchasaerospace,automotives,shipbuild-ingandmedicine,itisdifficulttocreateaCADmodelofanexistingproductthathasafree-formsurfaceorasculp-turedsurface.Inthesecases,reverseengineering(RE)isanefficientapproachtosignificantlyreducetheproductdevel-opmentcycle.REreferstotheprocessesinwhichdesignersacquireadesignconceptofaproductfromdigitizationofaphysi-calmodel,andcreatetheCADmodeltorealizeapprox-imationtothephysicalmodel:themodelcreatedcanbereused,modifiedandoptimized5.ByREtechnology,thegeometricshapeofanexistingpartorproductismeasured.BasedonthismeasurementdataacompleteandcomplexCADmodeliscreated.REhastwokeytechnologies,i.e.digitizationofaphysicalmodelandcreationofitsCADmodel.E-mailaddress:(Y.Zhang).2.WorkingprocessesofREDifferingfromthetraditionaldesignideaandmethod,REtechnologyenablesonetostartadesignfromanexistingproductmodelbycombiningcomputertechnology,measure-menttechnologyandCAD/CAMtechnology.REhasbeenofinterestinmanydifferentbranchessuchasautomotives,shipbuilding,electronics,andmedicine.Itisoftenusedincasessuchasthefollowing3:(i)Whereaprototypeofthefinalproducthasbeenmod-eledmanuallyandthereforenoCADmodeloftheprototypeexists,e.g.claymodelinautomotivein-dustry.(ii)WhereaCADisintroducedinacompanyandallexist-ingproductsmustbemodeledinordertohaveafullydigitalarchive.Particularly,theCADmodelofacom-plexshapedpartismodeledbecauseitisdifficulttocreateitsCADmodeldirectly.(iii)WherecomplexshapedpartsmustbeinspectedandthereforetheREmodelcreatedwillbecomparedtoanexistingCADmodel.TheREprocesscanprincipallybeseenasaprocesschainthatiscomposedofthreemainoperationsasfollows5:(i)Digitizationoftheobject:Thethree-dimensionalshapeoftheproductisacquiredbyanyappropriatemeasure-mentmethod.0924-0136/03/$seefrontmatter2003ElsevierScienceB.V.Allrightsreserved.doi:10.1016/S0924-0136(03)00513-2Y.Zhang/JournalofMaterialsProcessingTechnology139(2003)472475473Fig.1.WorkingprocessesofRE.(ii)Processingofmeasureddata:Thethree-dimensionaldataacquiredisprocessedinordertofulfilltherequire-mentsofthefollowingoperation.(iii)CreationofaCADmodel:AcompleteCADmodeloftheproductmustbebuiltinordertorepresentallrelevantdataoftheproduct.Fig.1showstheworkingprocessesofRE.ThewholeprocessofREshouldbecomputeraided.3.EngineeringapplicationofREBasedonprincipleofREtechnologymentionedabove,theauthorsappliedREtechnologyinthedesignandmanu-facturingofthedieofadieselengine.Takingthecoredieoftheinletofadieselengineasanexample,thispaperdescribestheREprocesses,fromobjectdigitization,CADmodelreconstructiontoNCmachining.Theinletisthekeypartinadieselengine.Itinfluencesthecharacteristicofthedieselenginetoagreatextent.Becausetheinlethasverycomplexshape(seeFig.2),itisdifficulttocreateadigitalmodeloftheinlet,aswellastomanufacturethecoredieoftheinlet.TheauthorshavethereforetakenitasanexampletoresearchtheengineeringapplicationofREtechnology.Fig.2.The3Dmodeloftheinlet.3.1.EnvironmentofRETheenvironmentofREisalocalareanetwork(LAN),whichisbuiltwithtwowork-stations,twoNTwork-stations,threesetsofPC,acoordinatemeasurementmachine(CMM)andthreeNCmachines.Thehardwareplatformusesleveldispositionofwork-stationsandPCs.ThemainapplicationsoftwareutilizedistheUnigraphicsCAD/CAE/CAMinte-gratedsystemandKUMmeasurementsoftwareprovidedbythezesscompany.TheoperatingsystemsutilizedareHP-UX10.2onwork-stationsandWindowsNTonPCs.Fig.3showstheenvironmentofRE.Withcomputernet-work,theREprocesses,i.e.objectdigitization,processingofmeasurementdata,creationofaCADmodel,andNCmachining,arerealizedinaintegratedenvironmentoncom-puters.Fig.3.EnvironmentofRE.474Y.Zhang/JournalofMaterialsProcessingTechnology139(2003)472475Fig.4.NCmeasurementandsurfacereconstructionofthecoredieoftheinlet.3.2.DigitizationofthedieGenerally,themethodsofmeasurementofthree-dimensionalgeometryproductdataaredividedintotwoclasses,i.e.tactilemeasurementandopticalmeasurement.TheCMMisageneraltactilemeasurementdevice,andisbeingwidelyusedinindustrialenterprises1,2.Theau-thorsmeasurethegeometricshapeofthedieandacquiremeasurementdatausingCMMandKUMmeasurementsoftwarewithalinearscanmode.ThephysicalmodelofthedieisscannedonCMMusinga5mmdiameterprobewithastep-overacrossthemodelof5mminthefirstareaand1mminthecomplexarea(seeFig.4a).ThenumberofmeasurementpointsisautomaticallydeterminedbyCMMaccordingtothecurvaturechangeofthesurfacemeasuredonthetactilepoint.Inordertoavoidtrackslip,theprobestartstomeasurethesurfaceat4mmawayfromthebound-aryofthesurfacebeingmeasured.Onaverage,thereareabout1600measurementpointsacquiredforeachscancurve.3.3.ProcessingofmeasurementdataTheresultofamechanicaltracingprocessisastructuredpointsequenceswithalargenumberofpointsandalinestructure4.TheoutputdataoftheCMMarecoordinatevaluesofthecenteroftheprobeandnormalvectorsintheX,YandZdirectionatthepositionofthetactilepoint.Addi-tionally,theoutputformatofthemeasurementdatadoesnotaccordwiththedemandsofthecreationofaCADmodel.Thusonemustprocessthemeasurementdata.Theauthorhaveself-developedaprogramtorealizethetransformationoftheformatofthemeasurementdata.First,theformatofthemeasurementdataoutputmustbetransformedintoaformatthatcanbeacceptedbyUnigraph-icssoftware.Thenthemeasurementdataoutofthecontroltolerancemustbefilteredoutandinteractivelyprocessedinavisualizedway.ThedataprocessedcanbeuseddirectlyforthecreationofaCADmodelofthedie.3.4.CreationofaCADmodelofdieTheCADmodeliscreateddirectlyfrommeasurementdatausingUnigraphicsCAD/CAE/CAMsoftwareafterpro-cessingofmeasurementdataandtransformingofthedataformat.TherearetwowaysinthecreationoftheCADmodelfrommeasurementdatausingfree-formfeaturemodeling.Oneiscalledthecurvemode.Inthisway,theconstructioncurvesaregeneratedfrommeasurementdatafirst,andthenthesurfacecanbecreatedthroughtheconstructioncurvemeshgenerated.Anotheroneiscalledthesurfacemode,thesurfaceisgenerateddirectlyfrommeasurementdata2.Becausethemeasurementdataoutputarethecoordinatevaluesofthecenteroftheprobe,thesurfacegeneratedfrommeasurementdataisasurfaceoffsetfordistance,whichequalstheradiusoftheprobe,awayfromactualsurfacemeasured.Thusonehastooffsetthissurface.Thesurfacegeneratedisanalyzedthroughashadingsur-faceandsurfaceanalysisfunctioninordertocheckitscon-tinuityandsmoothness,aswellastheerrorsbetweenthesurfacegeneratedandthemeasurementpoints.Themaxi-mumerroris0.2mm,whichisacceptable.3.5.NCmachiningofthedieAftertheCADmodelofthedieiscreatedcompletely,onecandeterminetheNCmachiningprocessplanningandgeneratethecutterlocationforamanufacturingapplica-tion.FurthermachiningcodesaregeneratedthroughNCpost-processing.Finally,thedieismachinedbyanNCma-chinetoolusingitsCADmodelcreated.Fig.4showstheresultsofNCmeasurementandsurfacereconstructionofthecoredieoftheinlet,whilstFig.5showsthegeneratedCADmodelofthecoredieoftheinlet.Fig.5.ThegeneratedCADmodelofthecoredieoftheinlet.Y.Zhang/JournalofMaterialsProcessingTechnology139(2003)4724754754.ConclusionBasedonpreviousresearchonREtechnology,theauthorshaveexploredtheengineeringapplicationofREtechnol-ogyinthedesignandmanufacturingofacomplexproduct.Takingadieoftheinletofadieselengineasanexample,theyhavedescribedthewholeprocesses,fromobjectdigi-tization,CADmodelreconstructiontoNCmachining,andhavegainedagoodresult.REisanefficientapproachtosignificantlyreducetheproductdevelopmentcycleanden-sureproductqualitykinthedesignandmanufacturingofaprodu