JournalofMaterialsProcessingTechnology169(2005)1-4TechnicalnoteThedevelopmentof3DmodelsthroughrapidprototypingconceptsD.M.C.Santosa,A.E.M.Pertencea,H.B.Camposa,P.R.Cetlinb,aDepartmentofMechanicalEngineering,UFMG,CidadeUniversitria,Pampulha,31270-901,B.Horizonte,MG,BrazilbDepartmentofMetallurgicalandMaterialsEngineering,UFMG,RuaEspiritoSanto35,30160-030,B.Horizonte,MG,BrazilReceived6November2003；receivedinrevisedform6January2004；accepted8June2004AbstractThree-dimensionalmodelsarebeingincreasinglyusedasprototypesinvariousareasofmanufacturing,researchandeducation.Theyareespeciallyusefulintheevaluationofelementstypicalofmechanicaldesign,butarealsoimportantinarchitecture,medicine,arts,etc.Thesemodelscanbedevelopedusingvariousmethods,suchasmassmodeling,surfaceplanification,andrapidprototyping(RP)withremovaloradditionofmaterialbasedonaCAD/CAMplatform.Thislatterapproachwasemployedinthepresentpaper.Complexsolidsareformedthroughtheassociationofelementarysolidssuchasspheres,prisms,cylinders,torus,etc.,andthenrapidprototypingisappliedinvolvingaslicingprocess.AvirtualmodelbasedonaCADplatformallowsthedeterminationofpathsforeachslicedlevel.Thesearetranslatedintonumericalcontrolcodes,andfedtoamillingprocessofablank,allowingthemanufacturingofa3Dmodel.2005ElsevierB.V.Allrightsreserved.Keywords:3Dmodels；Elementarysolids；Rapidprototyping1.IntroductionMechanicalpartsrepresentanimportantfractionofvari-ousproductswidelyusedinoursociety.Fiercecompetitiondemandsapermanentincreaseinproductivityandfasterre-sponsetochangingtechnicalandcommercialdemandsonsuchparts.Thishasledtowidespreaduseofautomaticde-signprocedures,basedoneithertraditionalmechanicsoronnumericalmethodssuchasfiniteelementanalysis(FEA),inordertoevaluatestressandstrainlevels.Suchanalysesde-mandaninitial3Dmodelingofthepartunderconsideration.Anincreasedinterestin3Dmodelsofmechanicalpartsisalsoobserved.Theseserveasprototypes,allowingtheanal-ysisoftheinterferencewithotherparts,ofthekinematicbehavioroftheproductandofthemanufacturingprocessestobeemployedintheproductionofthepart.Theconceptualizationandpreparationofsuchmodelsisofspecialimportanceintheeducationandresearchinme-chanicalengineering.Itallowsafarbetter3Dvisualizationofparts,leadingtoenhancedgeometricinterpretationandCorrespondingauthor.E-mailaddress:pcetlindemet.ufmg.br(P.R.Cetlin).0924-0136/$-seefrontmatter2005ElsevierB.V.Allrightsreserved.doi:10.1016/j.jmatprotec.2004.06.035spatialanalysisofmechanicalparts.Thisisofparticularim-portanceintheareasofmechanicaldesignandmanufacturingprocesses1,2.Thesemodelscanbedevelopedusingvariousmethods,suchasmassmodeling,surfaceplanification,andrapidpro-totyping(RP)withremovaloradditionofmaterialbasedonaCAD/CAMplatform.Thislatterapproachwasemployedinthepresentpaper.ComplexsolidsareformedthroughtheBooleanassociation(involvingaddition,subtractionandintersection)ofelementarysolidssuchasspheres,prisms,cylinders,torus,etc.,andthenrapidprototypingisappliedinvolvingaslicingprocess.AvirtualmodelbasedonaCADplatformallowsthedeterminationofpathsforeachslicedlevel.Thesearetranslatedintonumericalcontrolcodes,andfedtoamillingprocessofablank,allowingthemanufactur-ingofa3Dmodel.Figs.1and2illustratetheaboveprocedure.2.The3DFormprogramThe“3DForm”isacomputerprogramforthegenerationof3Dmodels,originallydevelopedattheFederalUniversityofMinasGerais,inBrazil.Itusestheassociationofelemen-2D.M.C.Santosetal./JournalofMaterialsProcessingTechnology169(2005)1-4Fig.1.Theassociationofelementarysolidsinordertoobtaina3Dmodel.tarysolidsinordertoobtaincomplexshapes.The“3DForm”worksasa“Client”program,controllingthegenerationoftheelementarysolids,andmanages“Slave”programssuchasaCADplatformofferingaprogramminginterfaceforexternaluseofitscommands3-5.The“3DForm”employedtheVisualBasicsixlanguageinordertocontrolanAutoCAD2000platform.Itsmainfeaturesarethefollowing:Controlofthegenerationofelementarysolids(spheres,prisms,cones,cylinders,etc.)inaCADplatform,atde-siredpositionsandwiththerequireddimensions.ApplicationofBooleanoperationsofaddition,subtractionandintersectionoftheabove-mentionedsolids,allowingtheconstructionof3Dmechanicalparts.Allowsthepermanenteditionvisualizationandprinting,fromvariousobservationviewpoints,ofthe3Dmechanicalpartsunderanalysis.SlicingofthepartsmodeledintheCADplatform,atanydesiredpositionandslicinginterval,leadingtoRPproce-dures.Capturing,treatingandstoringofthegeometricdatagen-eratedintheslicingprocess,foreachcuttingplaneinthemechanicalpart.DevelopmentofCNCcodefilesforapre-definedequip-ment,allowingthecreationofanautomaticsequenceforthemachiningofthecontoursofeachcuttingplaneandthephysicalmanufacturingofthemechanicalpart.Thegraphicalinterfaceofthe“3DForm”programpre-sentedinFig.3coversthecreationofcomplexsolidsbasedontheassociationofelementarysolids.Avisualizationtreeallowsthepermanenttrackingofthecreationhistoryoftheobject.Thistreecanbesavedinafile,eitherforacompletedFig.2.Slicingprocessleadingtomillingpaths.Fig.3.Mainscreenofthe3DFormprogram.orpartiallyconstructedpart.Theinterfaceisuserfriendlyandthecommandsareeasilyaccessible.Themainscreenofthe3DFormprogramisshowninFig.3,andcanbedividedintofiveareaswithpre-definedfunctions:Theregionofthemaincommandsisintheupperpartofthescreen.Itcontainsthecommandsforobjectcreation,forBooleanoperations,forthegenerationofGcodes,etc.Theregionintheupperleftregionofthescreendisplaystheinstantaneouscreationsequenceofthepart,allowingacleartrackingofallthestepsfollowedbytheuser.Theregionintheupperrightregionofthescreendisplaysthevisualizationcommands,involvingthedefinitionofpreferentialviewsandofthecolorsofthecreatedsolids.Theregioninthelowerleftofthescreenallowsthein-troductionofthedataforthecreationoftheelementarysolids.Thisdataispermanentlysavedandcanbeaccessedatanymoment.The3Ddrawingcanbeviewedtherightlowerregionofthescreen.Thefollowingoptionscanbeused:orbitalposi-tioning,zoom,shading,panandbackgroundcolor(blackorwhite).Itisalsopossibletodisplaythelimitsoftheselectedobject,asshowninFig.4.Fig.4.Visualizationofthelimitsofanobject.D.M.C.Santosetal./JournalofMaterialsProcessingTechnology169(2005)1-43Aspecialsystemfortheopening,savingandrecoveryofthedrawingwascreated,inordertofacilitatestoppingandre-startingoftheprojectatanytime.Savinginvolvestwotypesoffiles:onecoversalloperationstepsuptothesavingmoment,whereastheotherincludesthelastdrawingversion.3.RapidprototypingthroughmaterialremovalThemanufacturingprocessemployedinthepresentRPworkinvolvedmaterialremovalthroughmachininginasmallscaleCNCmillingmachine(EMCOPCMILL50).Accord-ingtoErbe6,suchRPstartswiththeslicingofavirtualmodel(presentlyfullyperformedby3DForm)followedbythecreationofmachiningpathsforaCNCmachine.Thesewereexecutedinthemillingmachine,resultinginaprototype7,8.Thenumberofslicesischosenbasedonthedesiredcut-tingdepthinthemachiningprocess.The“3DForm”pro-gramgeneratesthe“G”codesfortheCNCmachiningofeachslice.Thesearethengroupedincodeblocksandsomecomplementarycodesareadded.Theseinvolveinstructionssuchaschangesoftheoriginoftheequipmenttotheori-ginofthemodel,definitionofthetooltypesandofma-chiningparameters,changesintoolsandinblankposition,etc.Beforefinalmanufacturingoftheprototype,itisnecessarytomakesomesimulationsandtests,inordertoverifypossibleproblemsinthecodes,eventualincompatibilitiesbetweenthesecodesandthosefortheequipment,orsomeothererrors.Fig.5illustratesthesimulationofa3DmodelandFig.6showsthecorrespondingmodelmachinedintheCNCmillingmachine(EMCOPCMILL50).Fig.5.Simulationofa3Dmodel.Fig.6.PhysicalmodelobtainedinthesmallscaleCNCmillingmachine(EMCOPCMILL50).4.ConclusionsThedevelopmentof3DmodelsusingRPthroughmaterialremovalisveryinteresting,especiallyforthemanufacturingofsmallpartsandinmechanicalengineeringteaching.ThematerialremovaltechniqueforRPprovedquiteversatile,allowingthemachiningofthinsectionsandcomplexshapes.Forteachingpurposes,variousprototypesweremachinedinNylonandinAluminum,andreplacedthetraditionaltech-nicalandisometric(isometrical)drawings.Theeducationalresultssurpassedbyfarpreviousresultsbasedonthetradi-tionalapproach,especiallyfromthepointofviewofgeo-metricinterpretationcapacity,aimingatmachinedesignandmanufacturingprocessesevaluation.AcknowledgementsTheauthorsgratefullyacknowledgefinancialsup-portfromFundaodeAmparoPesquisadeMinasGerais(FAPEMIG),ProgramadeNcleosdeExcelncia,MCT(PRONEX),ConselhoNacionaldeDesenvolvimentoCientficoeTecnolgico(CNPq),FinanciadoradeEstudoseProjetos(FINEP),CoordenaodeAperfeioamentodePes-soaldeNvelSuperior(CAPES)andServioNa