Part5:3DPrintingCAD/CAM:PrinciplesandApplications(CAD/CAM原理與應(yīng)用)CollegeofMechanicalandElectricalEngineering,HohaiUniversity（河海大學(xué)機(jī)電工程學(xué)院）Associateprof.康蘭

Historyof3DPrinting3DPrintingProcess3DPrintingMaterialsContents3DPrintingBenefitsandChallengesWhatis3DPrinting?PrinciplesBehind3DPrintingAnOverviewof3DPrintingIndustryContentsApplicationsandtheFutureof3DPrintingAcquiringa3DModelTheEmergingApplicationsof3DPrinting4Dprinting

Will3DPrintingReplaceConventionalManufacturing?

CaseStudiesHistoryof3DPrintingThetechnologyforprintingphysical3DobjectsfromdigitaldatawasfirstdevelopedbyCharlesHullin1984.Historyof3DPrintingHullnamedthetechniqueasStereolithography

andobtainedapatentforthetechniquein1986.（Stereolithography）Hullwentontoco-found3DSystemsCorporation(oneofthelargestandmostprolificorganizationsoperatinginthe3Dprintingsectortoday.)Bytheendof1980s,othersimilartechnologiessuchasFusedDepositionModeling(FDM)andSelectiveLaserSintering(SLS)wereintroduced.Historyof3DPrintingIn2005,ZCorp.launchedabreakthroughproduct,namedSpectrumZ510,whichwasthefirsthighdefinitioncolor3DPrinterinthemarket.Anotherbreakthroughin3DPrintingoccurredin2008withtheinitiationofanopensourceproject,namedReprap,whichwasaimedatdevelopingaself-replicating3Dprinter.Inthepastyears,researchersandscientistsweretryingtoexplorenewapplicableareasof3Dprinting,especiallyinmedical

industryandaerospaceindustry.Studyingnewmaterialssuitablefor3Dprinting.Historyof3DPrintingBioprinter,4Dprinting.“3Dprintedcar”,“3Dprintedkidney”,“3Dprintedmetalparts”,……AnOverviewof3DPrintingIndustry1.

InfluentialCompaniesin3DPrintingIn2014,Appinionsliststhe“TenMostInfluentialCompanies”in3Dprinting(MakerbotwasacquiredbyStratasysin2013).Autodesk,Inc.TheCalifornia-basedsoftwarecompanyhasbeeninvolvedin3Dtechnologiesandprogramsforyears,itunveileda3Dprintingopensoftwareplatformandintroduceditsown3Dprinter.The3Dprintingmarketismaturingrapidly,"asattentionandinfluenceshiftsfromthecompaniesthatmanufacturetheseamazingdevicestoabroadrangeofindustrieswherethetechnologyisfindingdistributionandpracticalapplications".That'sonekeyfindingfromanewstudybythemarketersanddatajournalistsatAppinions.A,Inc.AppinionsaysAmazon'sinfluenceasaretailgiant,alongwiththecompany'srecentintroductionofa3Dprinteditemsmarketplace,pusheditintothenumbertwospot.AnOverviewof3DPrintingIndustryStratasysLtd.(SSYS)headquarteredinMinnesota,focusesonboththecommercial3Dprintingmarketandalsotheconsumer,desktop,3Dprintingmarket.StratasysLtd.wasformedthroughthe2012mergeroftwoprominent3Dprintingfirms,StratasysInc.,andObjetLtd.In2013,SSYScompletedtheacquisitionofMakerBotIndustries,aleaderindesktop3Dprinting.3DSystemsCorporationinvented3Dprintingin1989withitsinventionandpatentingofitsstereolithographytechnology.3DSystemshasalsodevelopedadditionaltechnologies,includingselectivelasersintering,multi-jetprinting,filmtransferimaging,colorjetprinting,directmetalprintingandplasticjetprinting.AnOverviewof3DPrintingIndustryOfcourse,Fromatechnicalpointofview,StratasysLtdand3DSystemsCorporationarestillthekeyplayersin3Dprintingindustry.AnOverviewof3DPrintingIndustryGlobal3Dprintermarketsharein20132.Global3DprintermarketshareGlobal3Dprintermarketsharein2015showsthatStratasysand3Dsystemsarestillinthefirstandsecondposition.AnOverviewof3DPrintingIndustryMachineindustryAerospaceMedical/dentalindustryConsumergoodsCarsOthersArchitecture

MilitaryindustryEducation3.Global3Dprintingapplicationanalysis(in2013)4.Global3Dindustrial-gradeprintermarketshare(2013)ItalyBritishChinaGermanyJapanAmericaOthersCanadaSouthKoreaFranceAnOverviewof3DPrintingIndustry5.Globalmajorprospectsinthe3DprintermarketAnOverviewof3DPrintingIndustry

CompetitiveFocusProducePrintingMaterialsDevelopmentofCoreTechnologyDeskTopPrintersProfessionalSupplyofMaterialsAnOverviewof3DPrintingIndustryMostCompetitiveAreasPersonalUseMoldIndustryMilitaryIndustryAerospaceislowvolumeproductionandisideallysuitedfor3Dprinting.Partscannowbecreatedwithcomplexgeometriesandshapesthatinmanycasesareimpossibletocreatewithout3Dprinting.Thisisalsoanattractiveareafor3Dprinting.Ascheaper3Dprintinghardwareentersthemainstream,moreandmorepeoplewillhaveatleastthepotentialtostart3Dprintingthingsathome,

andsomesmallcompanieswillalsoprintcustomizedorpersonalizedproducts.Consumeroptionsfordesktopswillrise.Comparingwithtraditionalwayofproducingmolds,3Dprintingprototypemoldsin-houseoffersafast,affordablewaytoproduceinjectionmoldedprototypes.Designersandengineerscantesttheirworkmorefrequentlyandmoreaccurately,andgotoproductionwithconfidence.

Basically,3Dprinterscanbecategorizedintotwotypes,desktopandindustrial-gradeones.AnOverviewof3DPrintingIndustry6.Typesof3DprintersThetypesof

3dprinters

canalsobedifferentiatedbytheirtechnologies,asshowninthesectionoftypesof3Dprinting.

Theindustrial-grade3dprintersareexpensiveandusedforthecreationofprototypesformanufacturingfirms.Desktop3dprintersareforpersonalusewhichpricesarerelativelymuchlowerthanindustrial-gradeprinters.3Dprintingreferstotransformcomputerdigitalmodelsintophysicalrealitybybuildingthemupinsuccessivelayersofmaterial.Whatis3DPrinting?Otherterminology:RapidPrototyping(RP),DirectManufacturing(DM)orDirectDigitalManufacturing(DDM),AdditiveManufacturing(AM).Subtractivemanufacturing*3Dprintingwasasimpleversionofrapidprototypingtechnology,butnowwiththedevelopmentofindustrial-gradeprinters,3Dprintingisbecominganindustrialleveladditivemanufacturingtechnology.3DPrintingprocessDecidingwhatyouwanttomakeCreatinga3DcomputermodelSelectingthematerial(s)youwilluseSlicingthemodelintoprintablelayersSTL(3D,layerinformation),SCLorCLICreatingcommandsfortheprinterFabricationoftheobjectPost-processingPost-processing:Cleanandremovesupportmaterial,excessmaterials,paintingpartsetc.3DPrintingprocesssolidnamefacetnormalninjnk

outerloopVertex1

vx

vy

vz

Vertex2

vx

vy

vz

vertex3vx

vy

vz

Endloopendfacet

ASCIISTLFormatofa.STLfileThermoplastics1.ExtrudedMaterials3DPrintingMaterialsExperimentalmaterials：compositematerialsPolylacticacid(PLA))Acrylonitrilebutadienestyrene(ABS)Polycarbonate(PC)Polyamides(nylon)High-impactpolystyrene(HIPS)High-densitypolyethylene(HDPE)Fuseddepositionmodeling(FDM)systemsuseextrudedmaterials.3DPrintingMaterialsFilament:spoolsofplasticwitha1.75mmor3mmdiameter.3DPrintingMaterials3D-printedlightpipesinDisney’sPrintedOpticExamplesof3Dprintedproductbyusingextrudedmaterials.3DPrintingMaterialsExtrudedalternatives:chocolate3D-printedchocolatebunny3DPrintingMaterialsExtrudedalternatives:3D-printedpancake(developedby吳一黎,施侃樂(lè))3DPrintingMaterials2.GranularMaterialsPlasticpowdersSugarandsalt3DprintingusingsugargranulesMetalpowdersA3Dprintedtitaniumjointimplant3DPrintingMaterialsSandandnaturalgranularmaterialsAsolar-powered3DprinterbuiltbyMIT’sMarkusKayserandtheprintedobject3DPrintingMaterials3.BioMaterialsBioprintingfoodandanimalproductsTheideabehindBioprintingfoodandanimalproductsistocreatelivingtissueslikemeatwithouttheneedforkillinganimals,andbioprintingleatherproduction.ReplacementtissuesandorgansTheideabehindreplacementtissuesandorgansistobioprinttissuesandorgansfromourowncells,soanti-rejectionmedicationsandwaitinglistsforbiocompatiblematcheswillberelicsofabygoneera.3DPrintingMaterials4.AlternativeMaterialsRecycledmaterialsPrintingstructuresbyusingcontourcrafting3DPrintingMaterials3Dprintedmodelsmadewithpaper3DPrintingMaterials3DPrintingBenefitsandChallenges

1.Benefitsof3DPrintingCustomizationComplexityTool-lessSustainable/Environmentallyfriendly2.

LimitationsandChallengesof3DPrintingLimitationsformassproductionRoughsurface3DPrintingBenefitsandChallengesLesssecurityLiabilityissuesIntellectualpropertyissuesEthicalissuesinmedicineOthersocialsecurityissuesPrinciplesBehind3DPrinting1.Typesof3DPrintingFusedDepositionModelling(FDM)FDMis“materialextrusion”Materialextrusion3Dprinting―withasinglenozzleBasicprinciplebehindFDMEden260VS3DprinterandtheprintedobjectPrinciplesBehind3DPrintingExamplesofFDM:PrinciplesBehind3DPrintingA3DprinterwithtwonozzlesPrinciplesBehind3DPrintingSchematicdiagramofdualextrusion3DprinterPrinciplesBehind3DPrinting2.PolyjetBasicprinciplebehindPolyjet3DprintingPrinciplesBehind3DPrintingExampleofmulti-material3Dprinting3.StereoLithography(SLA)BasicprinciplebehindSLAPrinciplesBehind3DPrintingPrinciplesBehind3DPrinting4.SelectiveLaserSintering(SLS)BasicprinciplebehindSLSPrinciplesBehind3DPrintingBasicprinciplebehindSLS

5.SheetLaminationBasicprinciplebehindsheetlaminationPrinciplesBehind3DPrintingExamplesofpaperprintedobjects（sheetlamination）PrinciplesBehind3DPrintingAcquiringa3DModelHowtoacquirea3Dmodel?

UsingaCADProgramScanninganExistingObjectDownloadingorBuyingaModelfromtheWebApplicationsandtheFutureof3DPrinting1.TheApplicationsof3DPrintingPersonalizedObjects

IndustriesA3DprintedconceptcarunveiledbyEDAG(1)Conceptmodeling(2)

PhysicalandfunctiontestingApplicationsandtheFutureof3DPrintingExamplesofprintedmolds(3)

Printingjigs,fixtures,patterns,molds,anddiesTheoriginalUrbee1ApplicationsandtheFutureof3DPrinting(4)

Automotive3DprintedpartsusedinaerospaceApplicationsandtheFutureof3DPrinting(5)AerospaceAdronewith150piecesofthefrontpart3DprintedForhobbyistsandenthusiastsofdrones,the

S(3D

printing

marketplace)setupashopfor3Dprinteddroneparts.ApplicationsandtheFutureof3DPrintingShop

for

drone

parts

in

the

shapeways

3D

printing

marketplaceApplicationsandtheFutureof3DPrintingApplicationsandtheFutureof3DPrintingAprintedairplaneshell3Dprintedstructures(6)ArchitectureApplicationsandtheFutureof3DPrinting

D-ShapeprinterinventedbyEnricoDiniAprintedgianteggwithlargeholesshoesApplicationsandtheFutureof3DPrinting(7)Consumerproductsclothesguitarstoysjewelries(8)MedicalindustryApplicationsandtheFutureof3DPrintingApplicationsandtheFutureof3DPrintingAdesktopinjectprinterusingcellsApplicationsandtheFutureof3DPrintingTheorganprinterandtheprintedkidneydonebyAtalaandhisteamApplicationsandtheFutureof3DPrintingCuringthewoundbyusingscanningandprinting3DprintertoprintrightonthepatientsApplicationsandtheFutureof3DPrintingAprintedplastermodelsAskingraftprinter1.EducationTheEmergingApplicationsof3DPrintingTeachingdesign,engineering,andartAfter-schoolactivitiesThespecial-needsstudentScientificvisualizationThecrystalstructures,3DprintdesignbyGeorgeHartThefollowingexamplesshowsomegeometricallycomplexmathematicmodelscanbevisualizedbyusing3Dprinting.TheEmergingApplicationsof3DPrinting3DprintdesignsbyBathshebaGrossmanTheEmergingApplicationsof3DPrinting3DprintdesignsbyHenrySegermanandSaulSchleimerTheEmergingApplicationsof3DPrinting2.PrintingFoodTheEmergingApplicationsof3DPrintingWeddingcaketoppersTheEmergingApplicationsof3DPrintingAchocolate3DprinterandtheprintedchocolatesTheEmergingApplicationsof3DPrintingMakingsugar-richcoatingbyprintingTheEmergingApplicationsof3DPrintingPancakeBot—theworld'sfirstpancakeprinter201320142015TheEmergingApplicationsof3DPrintingHopefullyprintingbeefsteakintheFuture!4Dprinting4DprintingpipesAself-foldedletterfromasinglestrandAself-foldedcubefromasinglestrandWill3DPrintingReplaceConventionalManufacturing?Aswelooktothefuture,it’sclearthat3Dprinting’sroleinmanufacturingwillonlygrow.Itwon’tentirelyreplaceconventionalmanufacturing.Therefore,inthefuture,3Dprintingandconventionalmanufacturingwillcompetewitheachother,meanwhileworkhandinhand,andprovidebetteroptionsformanufacturersandcustomers.CaseStudiesInthissection,wewillshowtheprocessof3Dprintingbasedoncasestudieswhichwillbefinishedinlab.Anotheroptionistoguidestudentstovisitalocal3Dprintinginnovationcenterandobservetheprocessofdifferent3Dprinting,evenletthemhaveahands-onexperienceifitispermitted.Inthefuture,ifstudentsarereallyinterestedin3Dprintingtechnology,andtheywouldliketodoresearchworkin3Dprintingarea,theyalsohavechancestoinvolveinprojectsprovidedbythecompany.END

Thegreatestthingsaredonebytheaidofsmallones.主講人：康蘭CAD/CAM:PrinciplesandApplicationsCAD/CAM原理與應(yīng)用CollegeofMechanicalandElectricalEngineering,HohaiUniversity（河海大學(xué)機(jī)電工程學(xué)院）

Part6:IntegrationofCAD/CAMandCIMs6.1IntroductionContents6.2InitialGraphicsExchangeSpecifications6.3

StandardfortheExchangeofProductModelData6.4STEP-NC6.5FeatureRecognition6.6GroupTechnology6.7CMIs6.1IntroductionIntheearlydays,CADandCAMweredesignedseparately,ThemainfunctionofCAMsystemswastoallowmanufacturingandtoolingengineerstowritecomputerprogramstocontrolmachinetooloperationssuchasmillingandturning.ButtherewasnocommunicationbetweenCADandCAMsystems.ThedevelopmentofCADandCAMtechnologyhassignificantlyincreasedefficiencyineachindividualarea.Theindependentdevelopment,however,greatlyrestrainedtheimprovementofoverallefficiencyfromdesigntomanufacturing.6.1IntroductionCurrently,thesimpleintegrationbetweenCADandCAMsystemshasbeenachieved.However,theseamlessCAD/CAMintegrationhasnotyetbeachieved.ThefirstefforttobreaktheisolationofCADandCAMsystemswastocreateastandardproductdataformatofanobject.IGESandSTEPformatsareconsideredastwoofthepopularstandardformats.ThesecondeffortistodevelopSTEP-NCtoaddresstheaboveproblemtoo.STEP-NCbasedhigh-levelmachiningsimulationsintegratesCAD/CAPP/CAMinawaythatallowstwo-waycommunicationbetweenCAD,CAPPandCAMsystems.ButcurrentlySTEP-NCisinitsinitialtestphase.6.2InitialGraphicsExchangeSpecifications

ProductdatasharingandtransferringacrossdifferentsystemsisanimportantparttoCAD/CAMintegration.ItcanmakedifferentCAD/CAMsystemscommunicatewitheachother.Therearemainlytwotypesofdatatranslators:

directtranslatorsandneutraltranslators.1.Introduction6.2InitialGraphicsExchangeSpecificationsDirectandneutraldatatransferThetwoprimaryneutralstandardformatsusedtodayareIGES(InitialGraphicsExchangeSpecification)andSTEP(StandardfortheExchangeofProductModelData)formechanicalproductdataexchange.IGEStranslators6.2InitialGraphicsExchangeSpecifications6.2InitialGraphicsExchangeSpecifications2.StructureofIGESFilesIGESisbasedontheconceptofentities.Entities:simplegeometricobjects,suchaspoints,lines,plane,andarcs.ormoresophisticatedentities,suchassubfiguresanddimensions.EntitiesinIGESaredividedinthreecategories:(1)Geometricentities:suchasarcs,lines,andpointsthatdefinetheobject.6.2InitialGraphicsExchangeSpecifications(2)Annotationentities:suchasdimensionsandnotesthatareaddedinthedocumentationandvisualizationoftheobject.(3)Structureentities:ThosedefinetheassociationsbetweenotherentitiesinIGESfile.IGESfileiswrittenintermsofASCIIcharactersasasequenceof80characterrecords.AnIGESfileconsistsoffivesectionswhichmustappearinthefollowingorder:Startsection,Globalsection,DirectoryEntry(DE)section,ParameterData(PD)section,andTerminatesection,6.2InitialGraphicsExchangeSpecificationsIGESfilestructurethenamesofthesendingandreceivingCAD/CAMsystems,abriefdescriptionoftheproductbeingconverted.asinglerecordwhichspecifiesthenumberofrecordsineachofthefourprecedingsectionsforcheckingpurposes.informationthatdescribethepreprocessorandinformationneededbythepostprocessortointerpretthefile.6.2InitialGraphicsExchangeSpecifications

DirectoryEntrySection(DE)Structureofdirectorysection6.2InitialGraphicsExchangeSpecificationsParameterDataSection(PD)Structureofparameterdatasection6.2InitialGraphicsExchangeSpecifications3.BasicIGESEntities(1)Line(entity110)(2)CircularArc(entity100)(3)TransformationMatrix(entity124)(4)SurfaceofRevolution(entity120)(5)Point(entity116)(6)Direction(entity123)(7)Planesurface(entity190)6.2InitialGraphicsExchangeSpecifications(10)Loop(entity508)(11)

Face(entity510)(12)Shell(entity514)(13)RightCircularCylindricalSurface(entity192)(8)VertexList(entity502)(9)EdgeList(entity504)6.2InitialGraphicsExchangeSpecifications4.AnExampleofIGESFiles6.2InitialGraphicsExchangeSpecifications5.LimitationsofIGESIGESprovideslimitedsupportfordifferentdatatypesandapplications.Productdataincludesaverywiderangeofdatatypes,notjustCADgeometry.AnotherbigshortcomingofIGESisthatthereismorethanonewaytodescribesomeentities.Forinstance,acubicsplinemaybepresentedasIGESentity112orentity126orevenasapolylineofpoints(entity106).Hence,acompletelynewapproachwasneeded.6.3StandardfortheExchangeofProductModelData(STEP)1.Introduction

STEPwasdevelopedasaninternationaldataexchangestandardsince1990s.ItbecameafullISO(InternationalStandardsOrganization)standardin1994andbynoweverymajorCADsystemvendorhasimplementedSTEPdatatranslation.STEPovercomestheshortcomingofIGESandgivesanexplicitandcompleterepresentationoftheproductdatamodel.STEPalreadycontainsdefinitionsforgeometry,productidentification,productstructure(assembly),configurationcontrolandmanufacturingfeatures.Inrecentyears,workhasbeendoneonincludinginformationfortooling,manufacturingstrategies,manufacturingprocessesandmaintenance.6.3StandardfortheExchangeofProductModelData(STEP)STEPwasdesignedtosupportaverywidevarietyoffunctionalandbusinessrequirements.Itcontainstheproductdatacoveringtheentireproductlifecycleandhasaneutralformatthatisindependentofanysoftwarepackageandunrestrictedtoanyparticularhardwareplatform.Thegeometrymodelsatisfiestherequirementsofthecomputer-basedrepresentationoftheshapeofaspecificproduct,butitisunabletodescribenon-geometricproductinformation.6.3StandardfortheExchangeofProductModelData(STEP)6.3StandardfortheExchangeofProductModelData(STEP)2.AnExampleofSTEPFilesThefilecontainstwosections:HEADERsection,DATAsection6.4STEP-NC1.IntroductionCurrently,"G-code"functionsasalinkorabridgebetweenCAD/CAM/CNCsystems.Asaresult,portingprogramsbetweenmachinesisdifficult.CurrentsituationsinCAMsystemsandCNCmachines6.4STEP-NCThebasicideabehindSTEP-NCisthatitremediestheshortcomingsof''G-code''byspecifyingmachiningprocessesratherthanmachinetoolmotion,usingtheconceptofworkingsteps.Workingstepscorrespondtohigh-levelmachiningfeaturesandassociatedprocessparameters.CNCsareresponsiblefortranslatingworkingstepstoaxismotionandtooloperation.ThereplacementforG-codeisso-called''STEP-NC'',thenameSTEP-NCmeaningtheSTEPstandardextendedforNC.STEP-NCisanewmodelofdatatransferbetweenCAD/CAMsystemsandCNCmachines.6.4STEP-NCSTEP-NCispromisingonCAD/CAMintegrationalthoughitsdevelopmentisstillintheinitialexperimentalstage.AmajorbenefitofSTEP-NCisitsuseofexistingdatamodelsfromSTEP.Basically,thestandardisthesmoothandseamlessexchangeofpartinformationbetweenCAD,CAM,andNCprogramming

asshowninthefollowingFigure.6.4STEP-NCFuture'sCAMandCNCunderSTEP-NC6.4STEP-NCTheSTEP-NCworksinanewwayofactioninmanufacturinglifecycle,fromdesigntofabrication.ThefollowingFiguresareacomparisonbetweenthecurrentCAD/CAM/CNCwayandthewaysupportedbySTEP-NC.6.4STEP-NCThecurrentwayofactioninmanufacturinglifecycle6.4STEP-NCOverviewofSTEP-NCprocessmodel6.4STEP-NC2.STEP-NCDataModelThecurrentmachine-toolprogrammingstandardistheISO6983(G-codes)datingbacktotheearly1980s.Thisstandardwithlowlevelinformationdescribeselementaryactionsandtoolsmoves,stronglyreducingpossibilitiesattheCNClevel.Itslinearlysequentialnature(seethefollowingFigure)breakstheCAD–CAM–CNCnumericalchainandmakesgatheringfeedbackfromtheshopfloordifficult.TheG-codesstandardisoneofthemainlimitationstoflexibilityandinteroperability.6.4STEP-NCCurrentG-codeprogrammingThisstandardwithlowlevelinformationdescribeselementaryactionsandtoolsmoves,stronglyreducingpossibilitiesattheCNClevel.TheG-codesstandardisoneofthemainlimitationstoflexibilityandinteroperability.6.4STEP-NCNewSTEP-NChighlevelprogrammingSTEP-NCprovidesnewopportunitiestosupporthighlevelandstandardizedinformationfromthedesignstagetofabricationbyanNCcontroller.6.5FeatureRecognition1.IntroductionWhyisfeaturerecognitionneeded?Andwhatisfeaturerecognition?Thebridgebetweendesignandmanufacturingisprocessplanning.Processplanningistheprocessofdeterminingdetailedoperationinstructionstotransformanengineeringdesigntoafinalpart.NowadaysComputerAidedProcessPlanning(CAPP)isusedtoautomatetheprocessplanning.6.5FeatureRecognitionCADandCAMsystemsusedifferentsetsoffeaturesindesignandmanufacturing.SoinCAPP,aprocesscalledfeaturerecognition(FR)distinguishesthemanufacturingfeatureofapartfromthegeometryandtopologicaldatastoredintheCADsystem.Usually,therearethreedistinctstagesinmostFRmethods.(1)Extractasetoffacesorothergeometric/topologicalelementsthatcanpotentiallyformafeature.6.5FeatureRecognition

（2)Describeeachfeaturetoberecognizedasacombinationofgeometric/topographicelements.

（3)Thethirdandfinalstepinvolvescomparingtheextractedpatternwiththepre-definedsetoffeaturetemplates.Whataremanufacturing/machiningfeatures?Firstthinkaboutdesignfeaturesmentionedbefore.6.5FeatureRecognitionClassificationofmachiningfeatures6.5FeatureRecognitionExamplesofmachiningfeatures

6.5FeatureRecognitionGeneralmachiningfeaturesb)Transitionfeaturec)Compound/regionfeatured)ReplicatefeatureManufacturingfeatures6.5FeatureRecognition2.FeatureRecognitionNotice:ThefieldofFRisquitebroad,andtheexistingFRmethodscanbeclassifiedbasedondifferentcriteria.Forexample,FRtechniquesrelatedtodifferentCADsystems;FRtechniquesusedinCAPP.InthissectionFRreferstothelaterone.Flowchartforafeaturerecognitionsystem6.5FeatureRecognition3.FeatureRecognitionTechniques6.5FeatureRecognitionBoundaryrepresentationBoundaryrepresentation(orsurfacerepresentation)usesacollectionoffacesinthesolidmodeltorepresentfeatures.Surfacerepresentationprovidesanaturalwaytoassociateimportantmanufacturinginformationsuchastolerancesandsurfaceroughnesswiththefeatures.VolumetricrepresentationVolumetricrepresentationrepresentsfeaturesbyusingsolidvolumesthatcanberemovedfromtheworkpieceinamachiningoperation.6.5FeatureRecognitionTherehasbeenanincreaseduseofvolumetricrepresentationinrecentresearchasitprovidesamorecomprehensiverepresentationoftheactualmachiningoperationsthansurfacerepresentation.However,thepurevolumetricrepresentationisnotsuitedtohandledesignandprocesschangesanditcannotbeclearlyrelatedtotheassociatedfacesofthedesignmodel.ThefollowingFigureillustratesexamplesofsurfaceandvolumetricrepresentationsofthesamepart.6.5FeatureRecognitiona)Solidmodelandfeaturesb)Surfacerepresentationsc)Volumetricrepresentations6.5FeatureRecognitionRule-basedapproachRule-basedapproachdeterminessometypicaltemplatepatternsoffeatures,whichexpressesthecharacteristicrelationshipbetweentheentitiessuchasfaces,loops,edgesandvertices.EmployingcharacteristictraitsorsignaturesthatidentifytheexistenceofafeatureiscommoninpublishedFRmethodology.Essentially,graph-based,hint-based,rule-basedandneuralnetworkscanbe

categorizedintorule-basedapproach.6.5FeatureRecognitiona）Partb)Attributeadjacencygraphc)RecognizedfeaturesAnexampleofgraphbasedpatternmatchingforfeaturerecognition6.5FeatureRecognitionTheprocessofrule-basedapproach:ThepartgraphshownintheaboveFigureissearchedfor