1、洛阳理工学院毕业论文第页1CAD/CAMComputertechnologyhasriseninanexponentialcurve/OnlyagenerationagocomputerswerenotreallyneededforNCcontrol/Exceptforrelativelyfewfive-axismachines/NCwaspointtopoint/whichwaseasilyaccomplishedwithmanualprogramming/Withtheadventoftwo-dimensionalprofiling/hower/aneedarosefornumerousc
2、alculationstogeneratethecurvedprofile/Atthatpointthecomputerwaslookeduponasausefultoolinmanufacturingengineering/Aftersomedevelopment/itwasfoundthatpunchedormagnetictapecouldbedispensedwithentirelyinfavorofcomputerprogramsthatcontrolledthemachinesdirectly/Thencametheminicomputers/whichwhenoperatingw
3、iththecentralprocessorbroughtaboutthefirstrealconceptoftheautomaticfactory/Allofthesedevelopmentswereimportantstepsintheadvanceoftechnology/Thecomputerisnolongerviewedasaremotepieceofhardwareusedprimarilyinaccountingandengineeringdepartments/butinsteadasanimportanttooltobeusedincreasinglyinCADandCAM
4、/TodayCADandCAMhavebecomecloselylinkedforcompleteprocessingfromdesigntoproduction/ThedesinengineercannowcreatethedesireddesignonaCRTscreenthatislinkedtoacomputerizedgraphicsplotter/Thesamesystemcanbeusedtodeterminetheviabilityofthedesignbyanalyzingstressesanddeflectionsthatwilltakeplaceunderloadingc
5、onditions/Thefunctioningofmechanicallinkagesmayalsobechecked/Afterthedesigniscomplete/theproductiongroupcandrawontheinformationdevelopedinCADforcomputer-aidedmanufacture/ThustheunifiedCAD-CAMteamhasbeendevelopedtobringtheproductfromthedesignconcept洛阳理工学院毕业论文第页2throughmanufacture/CADFunctionsInitiall
6、yCADsystemswereprimarilyautomateddraftingstationsinwhichcomputerplottersproducedengineeringdrawings/Thesystemswerelaterlinkedtographicdisplayterminals/whichallowedtheusertocommunicatewiththecomputerinpicturesinsteadofrawcolumnsofnumbers/Nowadvancedsystemshaveaddedanalyticalcapabilities/CADfunctionsm
7、aybegroupedintofourmajorcategories/geometricmodeling/engineeringanalysis/kinematics/andautomateddrafting/GeometricModelingTraditionally/engineersdothesketchinganddrafts-menthedrafting/Engineersthendiscoverneededchangesorimprovementsanddraftsmendraftwhatisrequired/Movingabracket2in/totheleftcausesane
8、ntreechainreactionthroughoutacompletesetofdrawings/Nowthecomputerhasopenedupanewwaytomeetdesignengineeringneedswithspeedandreliabilityinproductsrangingfromhigh-performanceaircrafttocomplex/integratedcircuits/Thedesignercansketchdirectlyonthescreenofagraphicsterminal/Linesandcontoursaredefinedbypress
9、ingkeysandpositioningalightpen/andthecomputerdisplayswhatisexpressed/Curvefitting/orreducingthedesigntoasetofcontrolequationsisdoneattheterminal/eliminatingcoding/cardpunching/punching/andrepeatedcomputerbatchruns；thenCADconvertsthepreliminarydesigntoadimensionaldrawingwithauxiliaryviews/Ifthedrawin
10、grevealsaproblemofcompatibilitywithasubassembly/thepiecescanbemovedaroundwiththelightpen/Thecomputerthenconvertsthispictorialrepresentationtoamathematicalmodelstoredinthecomputerdatabaseforlateruse/洛阳理工学院毕业论文第页3ThemodelmaybeusedorotherCADfuctionsoritmayberecalledandrefinedbytheengineeratanypointinth
11、edesignprocess/GeometricmodelingisoftenconsideredtobethemostimportantfeatureofaCADsystembecausesomanyotherdesignfunctionsinthesystemdependheavilyonthemodel/Thegeometricmodelmaybeusedtocreateafiniteelementmodelofastructureforstressanalysis/Themodelmayalsoserveasaninputforautomateddraftingtoproduceeng
12、ineeringdrawings/IfCAD/CAMsystemsareinterfaced/thegeometricmodelcanbeusedtocreateNCtapesforfabricatingthepart/Mostmodelingisdonewithawireframethatrepresentsthepartshapewithinterconnectedlineelements/AnalysisAfterthegeometricmodelingisdone/theCADsystemallowsthedesignertomovedirectlytoanalysis/Withsim
13、plekeyboardinstructions/thecomputerisaskedtocalculateweight/volume/surfacearea/momenttoinertia/orcenterofgravityofapart/However/themostpowerfulmethodofanalyzingapartisbythefiniteelementmethod/Inthistechniquethestructureisbrokendownintoanetworkofsimpleelementthatthecomputerusestodeterminestresses/def
14、lections/andotherstructuralcharacteristics/Suchanalysisrequiresthetremendouscomputationalpowerofamainframecomputer/KinematicsManyCADsystemhavekinematicfeaturesforplottingoranimatingthemotionofsimple/hingedpartssuchasdoorsorcranks/Suchanalysiscanensurethatmovingcomponentsdonotimpactonotherpartsofthes
15、tructure/Thedesignofanautomobilehoodlinkage/forexample/requiresonlyafewminutesofinteractionwithacomputer/whereashundredsofhoursofhourscanberequiredformanualdesignofthesamepart/洛阳理工学院毕业论文第页4Expertsbelievethatinthefuturecomputersandprogramswillbeavailabletocompletelysynthesizeacomplexmechanicalsystemb
16、asedsolelyonitsintendedfunction/DraftingWithautomateddrafting/detailedengineeringdrawingsmaybeproducedautomaticallyfromadatabase/Inaddition/mostdraftingsystemshaveautomaticscalinganddimensioningfeatures/AtypicalCADsystemwithautomateddraftingcangenerateuptosixviewsonthescreen/Anydesignchangemadeonone
17、viewisautomaticallyaddedtotheothers/CAMFunctionsCAMfunctionscenteraroundfourmainareas/numericalcontrol/processplanning/robotics/andfactorymanagement/NumericalcontrolAsstatedpreviously/NCusescodedinformationtocontrolmachinetoolmovements/ThecomputercannowgenerateaNCprogramdirectlyfromageometricmodelof
18、apart/Automaticcapillariesaregeneralitieslinkedtohighlysymmetricgeometricandotherspecializedshapes/ProcessPlanningProcessplanningisinvolvedwiththedetailedsequenceofproductionstepsfromstarttofinish/Essentially/theprocessplandescribesthestateoftheworkplaceateachworkstation/Theuseofcomputersasanaidtopr
19、ocessplanningiscomparativelyrecentandhasledtoarebirthofwhatisknownasgrouptechnology(GT)/Grouptechnologyisbasedonorganizingallsimilarpartsintofamiliestoallowstandardizationoffabricatingsteps/Currentlyunderdevelopmentisprocessplanningsystemthatisabletoproduceprocessplansdirectlyfromthegeometricmodeldatabasewithalmostnohuman
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