数控技术专业英语 教学课件 作者 黄义俊 电子教案统一模板(数控)Unit9.ppt

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1、Unit9TheSpecial-PurposeMachiningEquipmentLesson17Electro-dischargeMachines9.1Lesson18TypesofElectro-dischargeMachines9.2ReadingMaterials17Traveling-wireEDMMachine9.3ReadingMaterials18ElectrochemicalMachines9.49.1Lesson17Electro-dischargeMachinesElectricaldischargemachining(EDM),orelectro-di

2、schargemachining,orsparkmachining,asitisso-called,isbasedontheerodingeffectofanelectricsparkonboththeelectrodesusedtoproduceit.Whenapplyingtheelectro-dischargemachiningprocess,thematerialiserodedasaresultofanelectricaldischargebetweentoolandwork.AsinthecaseofECM,EDMisacopyingprocesswherethe

3、reisnocontactbetweentoolandwork.ContrarytoECM,thereissomeerosionofthetoolinEDM,whichmustbeallowedforinthetooldesigntoensureaccuracyofmachining.AfurtherdifferencearisesfromthefactthatinEDMthereisnofixedtoolfeed,butthegapsizemustbemaintainedinaccordancewiththerateofmetalremovalandthecondition

4、sexistingwithinthegap.[1]EDMisaformofmetalremovalinwhichpulsatingdirectcurrentisappliedtoashapedtool(electrode)andaworkpiece,bothofwhicharecapableofconductingelectricity.Thetwoareheldclosetoeachotherwithanon-conductingfluidservingasaninsulatorbetweenthem.Whenavoltagehighenoughtobreakdownthe

5、insulatorisreached,asparkjumpsinthegapbetweenthetoolandworkpiece.Asaresult,thissparkremovesasmallportionofmaterial.Themainadvantageisthatelectricaldischargemachiningprocesseswithgoodsurfacefinishandcanmachinemetalofanyhardness.9.2Lesson18TypesofElectro-dischargeMachinesTherearetwobasictypes

6、ofelectro-dischargemachinesdescribedasbelow：Electro-dischargedie-sinkingmachines—TheconstructionprinciplesofanEDMdie-sinkingmachineareshowninFigure9-1.Sparkerosiontakesplaceinacontainerfilledwiththedielectric,inwhichthework-pieceisclamped.Thecontrolledfeedoftheelectrodeisthroughanelectro-h

7、ydraulicorelectro-mechanicalservosystem.Theelectricalenergyforerosionisprovidedbytheerosiongenerator.Thefilteringunitseparatestheerodedmaterialfromthedielectric.Theappliedvoltageionizesthegapatthebeginningofthedischarge.Atthepointofthehighestfieldstrengt