特种加工复习指导_免费下载.docx

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1、第一章•DEFINITIONOFEDMElectricalDischargeMachining(EDM)istheprocessofmachiningelectricallyconductivematerialsbyusingpreciselycontrolledsparksthatoccurbetweenanelectrodeandaworkpieceinthepresenceofadielectricfluid,sotomakethesize，theshapeandthesurfacequalitymeetthepr

2、edeterminedrequirements.Theelectrodemaybeconsideredthecuttingtool.DifferentTypesofEDMDie・sinker(alsoknownasram)typeEDMmachinesrequiretheelectrodetobemachinedintheexactoppositeshapeastheoneintheworkpiece.Wire-cutEDMmachinesuseacontinuouswireastheelectrode・Sparking

3、takesplacefromtheelectrodewire-sidesurfacetotheworkpiece.SmallholeEDMdrilling(fastholeEDMdrilling).EDMDiffersFromMostChipMakingMachiningOperations1.electrodedoesnotmakephysicalcontactwiththeworkpieceformaterialremoval.2.EDMhasnotoolforce.3.electrodemustalwaysbesp

4、acedawayfromtheworkpiecebythedistancerequiredforsparking,knownasthesparkinggap.4.onlyonesparkoccursatanyinstant.(exceptforHSWEDM)(frequencyrangefrom2?000to1,000,000sparkspersecond)DielectricMaterialorDielectricFluidEDMisathermalprocess;materialisremovedbyheat.Mat

5、erialatclosestpointswherethesparkoriginatesandterminates,areheatedtothepointwherethematerialvaporizes・Thisdielectricmaterialisnormallyafluid.Die-sinkertypeEDMmachinesusuallyusehydrocarbonoil,whilewire-cutEDM(LSWEDM)machinesnormallyusede-ionizedwaterThePrincipleof

6、EDMTheworkpieceandtoolarcplacedintheworkpositionsothattheydonottouch.Agapremains,filledbythe"dielectric”.TheworkpieceandtoolareconnectedtoaD・C・powersourceviaacable・Aswitchisinsertedintheconnection.Whenclosed,anelectricalvoltageissetupbetweentheworkpieceandtool.Ma

7、inCharacteristicofDielectricFluid1Controllingthesparking-gapspacingbetweentheelectrodeandworkpieceasaninsulator;2CoolingtheheatedmaterialtoformtheEDMchip;3RemovingEDMchipsfromthesparkingarea;4Compressdischargechannel&causeexplosioninchannel.NecessaryConditionforE

8、DM:(5个)Sparkgap,Dielectricfluid,Powerfulpulsepower,SparkontimeisveryshortyEnoughsparkofftime。COMPARISONOFDIE-SINKERANDWIRE-CUTMACHINESBothdie-sinkerandwire-cut