特種加工資料

1、1、什么是什么是EDMElectricalDisgeMachining(EDM)istheprocessofmachiningelectricallyconductivematerialsbyusingpreciselycontrolledsparksthatoccurbetweenanelectrodeawkpieceinthepresenceofadielectricfluidsotomakethesizetheshapethesu

2、rfacequalitymeetthepredeterminedrequirements.2、EDM與傳統(tǒng)加工方法的差異與傳統(tǒng)加工方法的差異1）electrodedoesnotmakephysicalcontactwiththewkpiecefmaterialremoval.2）EDMhasnotoolfce.3）electrodemustalwaysbespacedawayfromthewkpiecebythedistancerequ

3、iredfsparkingknownasthesparkinggap.4）onlyonesparkoccursatanyinstant.(exceptfHSWEDM)(frequencyrangefrom2000to500000sparkspersecond)3、EDM的發(fā)展歷史的發(fā)展歷史In1943，theFirstEDMIntheWldIn1943theLazarenkosdevelopedasparkmachiningproces

4、swithanelectricalcircuitthatusedmanyofthesamecomponentsastheautomobileignitionsystem.ThisprocessbecameoneofthestardEDMsystemsinusethroughoutthewld.SincetheLazarenkoEDMsystemusedresistscapacitsitbecameknownasaresistcapaci

5、t(RC)circuitfEDM.4、WEDM機床的的發(fā)展歷史機床的的發(fā)展歷史約在1960年前蘇聯(lián)的科學院中央電工實驗室首先研制出第一臺低速走絲靠模仿形電火花線切割機床以后二三年中從靠模仿形又發(fā)展到光電跟蹤1962年前后瑞士阿奇公司開始研究電火花線切割加工的數(shù)字控制技術但在五六年后才達到實用化程度。我國科學院電子研究所1964年研制出光電跟蹤線切割機床這又是思維和技術上的一次飛躍?？奢^大地提高工作效率、縮短制造周期和降低加工成本增加了切

6、割更復雜型面的可能性提高了工藝的適應性和“柔性”。由于第一代線切割機床的絲速很低在煤油工作液中切縫較窄排屑不暢所切割速度很低只有2～5mm2min且電極絲一次性使用也很浪費。上海電表廠張維良工程師對此作了創(chuàng)新性改進在陽極機械切割工藝和機床的基礎上采用了往復、高速走絲和水基工作液(乳化液)使切割速度成倍、數(shù)十倍提高(大于10mm2min)且可進行大厚度切割。此后上海機床電器廠又和復旦大學數(shù)學系聯(lián)合研制出線切割簡易數(shù)控系統(tǒng)后經(jīng)用戶、生產(chǎn)廠、

7、科研院所、高校等的技術工人和科技人員多方面改進和完善形成了具有我國自主知識產(chǎn)權和中國特色的數(shù)控高速走絲電火花線切割機床品種。ThefirstmajeventintheevolutionofwirecutEDMwasnumericalcontrol(NC)in1960s.In1967awirecutEDMmachineproducedintheUSSRwasdisplayedatamachineexpositioninMontrealQu

8、ebecCanada.Thismachinefeaturednumericalcontrolwithpositioningbysteppingmots.TheUSSRwirecutEDMmachinewasprobablythefirstcommerciallyavailableunittobemarketed.5、電火花與線切割的比較、電火花與線切割的比較BothdiesinkerwirecutEDMmachinesusesparks

9、toremoveelectricallyconductivematerial.Butwhilebothtypesareelectricaldisgemachinestherearedifferencesintheiruseoperation.Dielectricfluid:diesinkerEDMmachinesusehydrocarbonoilsubmergethewkpiecesparkinthefluidThetransistal

10、lowselectricitytobeavailableatthesparkinggapduringtheONtimebutthesparkwillnotoccuruntilthedielectricfluidionizestoallowthepassageoftheelectricity.Therearetwodifferentconditionsthatcanthenoccur:1.thedielectricfluidwillnot

11、ionizeduringthetransistONtimewhenthevoltageisappliedacrossthesparkinggap2.thedielectricfluidwillionizeduringthetransistONtimewhenthevoltageisappliedacrossthesparkinggap.AdvantageofEqualONtimeSparking1）EqualONtimesparking

12、isbasedonstartingthesparkONtimeatthepointofdielectricfluidionization.2）IonizationtakesplaceONtimecommencesstaysonfthetimesetatthepowersupplycontrol.3）SparkingamperesflowonlyduringthetimeofionizationuntiltheOFFtimebegins.

13、4）Eachsparkhereisalwaysequal.5）EqualsparkONtimeensuresequalmaterialremovalfeachsparkallowsfconsistencyinthemachinedsurface.11、脈沖電源的一般要求、脈沖電源的一般要求1)脈沖電壓波形的前后沿應該很陡，即脈沖電流及脈沖能量的變化較小，減小因電極間隙的變化或極間介質污染程度等引起工藝過程的波動。2)脈沖是單向的，即沒有

14、負半波或負半波很小，這樣才能最大限度地利用極性效應，實現(xiàn)高效低耗的加工。3)脈沖的主要參數(shù)如電流幅值、脈沖寬度、脈沖間隔等應能在很寬的范圍內調節(jié)，以適應不同要求。4)工作穩(wěn)定可靠，操作維修方便，成本低，壽命長，體積小。GeneralRequirementsfPowerSupply1)Thefmerrearedgeofpulsevoltagewavefmshouldbeverysteepthatispulsecurrentpulseene

15、rgychangesinasmallrangethatcanreducetheprocessfluctuationscausedbyelectrodegapchangesthepollutionlevelofdielectric.2)Thepulseisunidirectionalthatisthereisnoverysmallnegativewavetomaximizetheuseofpolarityeffectsmachiningw

16、ithahighefficiencylowelectrodewear.3)Themainparameterssuchaspulsecurrentamplitudepulsewidthpulseintervaletc.shouldbeabletoadjustinawiderangetoadapttodifferentrequirements.4)Wkingstablereliableconveniencefoperationmainten

17、ancelowcostlonglifesmallsize.12、電感效應的總結、電感效應的總結Thefollowingpointssummarizewhathappenswithinductivereactance:1）inductivereactanceincreasesassparkfrequencyincreases2）inductivereactancecausesthetrailingedgeofthesparkwavefmt

18、oextend3）extensionofthewavefmtrailingedgedecreasesthetimefromonesparktothenext4）whenthetrailingedgeextensionincreasestothepointthatitconnectswiththenextsparkDCarcingwillresult.InductiveReactanceTheelectricaltermfimpeding