Unit-10-Electrical-Discharge-Machining-机电专业英语-图文课件.ppt

1、Unit 10 Electrical Discharge MachiningContentslNew Words&Expressions lText&TranslationlComplex Sentence AnalysislKey to ExercisesNew Words&Expressions lElectrical-discharge machining(EDM)电火花加工lpulsating plseiti adj.脉冲的，脉动的lDC(direct current)直流电ldielectric daiilektrik n.电介质，绝缘体 adj.非传导性的lmount maunt

2、v.安放，设置lelectrode ilektrud n.电极New Words&Expressions lservomotor s:vumut n.伺服电机lrectifier rektifai n.整流器lvibrator vaibreit n.振动器；振荡器lmulti vibrator 多频振荡器loscillator sileit n.振动器lcircuit s:kit n.电路，线路lvicinity visiniti n.附近，临近levaporate ivpreit v.蒸发；消失New Words&Expressions lvaporize veipraiz v.使蒸发lcr

3、ater kreit n.坑lerode irud v.侵蚀，腐蚀，逐渐消蚀掉lglobule glbju:l n.小球lservo-control n.伺机控制，随动控制lmicrosecond n.微秒；一百万分之一秒lservodrive 伺服传动装置；伺服控制lcavity kviti n.洞，穴New Words&Expressions lextrusion ekstru:n n.挤压（成型）ldie dai n.模具，冲模lgraphite grfait n.石墨，黑铅lcemented carbide 硬质合金，烧结炭化物lsinter sint v.烧结lhigh-aspect

4、-ratio 高深宽比，高纵横比lflush fl v.冲洗lfuel-injector nozzle 喷油嘴Text&TranslationlElectrical discharge machining(EDM)，which is also called spark machining，removes material with repetitive spark discharges from a pulsating DC power supply，with a dielectric flowing between the workpiece and the tool.Text&Transl

5、ationlThe working principle of the EDM process is illustrated by the simplified diagram in Fig.101.1The tool is mounted on the chuck attached to the machine spindle whose motion is controlled by a servo controlled feed drive.The workpiece is placed in a tank filled with a dielectric fluid；a depth of

6、 at least 50 mm over the work surface is maintained to eliminate the risk of fire.The tool and workpiece are connected to a pulsating DC power supply.Dielectric fluid circulates under pressure by a pump，usually through a hole(or holes)in the tool electrode.The servomotor maintains a spark gap of abo

7、ut 0.025 to 0.05 mm.Text&TranslationlIn power supply system of EDM，the input power is first converted into continuous DC power by conventional solid state rectifiers.The flow of this DC power is then controlled by a bank of power transistors which are switched by a digital multi vibrator oscillator

8、circuit.2The high power pulsed output is then applied to the tools and workpiece to produce the sparks responsible for material removal.Text&TranslationFig.10-1 Basic feature of electrical-discharge machiningText&TranslationlEach spark generates a localized high temperature on the order of 12 000 C

9、in its immediate vicinity.This heat causes part of the surrounding dielectric fluid to evaporate；it also melts and vaporizes the metal to form a small crater on the work surface.Since the spark always occurs between the points of the tool and work that are closest together，the high spots of the work

10、 are gradually eroded，and the form of the tool is reproduced on the work.The flowing dielectric fluid carries the condensed metal globules away，which are formed during the working process.As the metal is eroded，the tool is fed toward the workpiece by a servo controlled feed mechanism.Text&Translatio

11、nlEach pulse in the EDM cycle lasts for only a few microseconds.Repeated pulses，at rates up to 100 000 per second，result in uniform erosion of material from the workpiece and from the electrode.As the process progresses，the electrode is advanced by the servo drive toward the workpiece to maintain a

12、constant gap distance until the final cavity is produced.Text&TranslationlElectrical discharge machining can be used for all electrically conducting materials regardless of their hardness.The process is quite suitable to produce the sinking of irregularly shaped holes，slots，and cavities.Fragile work

13、pieces can be machined without any damages.Holes can take various shapes and can be produced at shallow angles in curved surfaces，in which case workers dont have to worry about the problem of tool wander.Text&TranslationlThe EDM process is widely used in tool making，especially in the manufacture of

14、press tools，extrusion dies，forging dies，and molds.Graphite electrodes produced by copy milling from patterns are often used.lA great advantage of EDM is that the tool or die can be machined after it is hardened and hence great accuracy can be achieved.3Tools of cemented carbide can be machined after

15、 final sintering，which eliminates the need for an intermediate partial sintering stage，thus eliminating the inaccuracies resulting from final sintering after holes，slots，and so on，are machined.Text&TranslationlElectrical discharge machining can be used effectively to drill small high aspect ratio ho

16、les.Diameters as small as 0.3 mm in materials 20 mm or more in thickness can be easily achieved.With sufficient flushing，holes with aspect ratios as high as 100 1 can be produced.The process has been used successfully to produce very small diameter holes in hardened fuel injector nozzles.Varying num

17、ber of holes in a precise pattern can be drilled around the injector tip.Text&Translationl电火花加工（EDM）或放电加工，它是通过脉冲直流电源不断地产生火花放电来去除工件材料的，工件与刀具之间有绝缘液体介质。Text&Translationl如图10-1所示为被简化的图，它描述了EDM工艺的原理。工具被安装在机床主轴的卡盘上，它的运动由伺服控制进给驱动。工件安装在一个盛满液体介质的箱中；液面至少在工作表面50 mm以上以排除燃烧的风险。工具和工件通过直流脉冲电源连接。液体介质通常通过工具电极上的一个孔（或

18、多个孔）在泵提供的压力下流动。约0.0250.05 mm的火花间隙能通过伺服电机保持。Text&Translation图10-1电火花加工的基本特征Text&Translationl在EDM电源中，输入电源首先被常规的晶体整流器转化成连续的直流电。随后直流电流由一组作为多频振荡器电路开关的功率晶体管控制。高功率脉冲输出到工具和工件中以产生可靠的电火花来去除材料。Text&Translationl每个电火花在它的附近产生规定的12 000 的局部高温。其热量导致零件周围的液体介质蒸发，它也融化和蒸发金属已在零件的工作面形成小坑。由于电火花总是发生在工具上的一些点与工件最接近处，工件的上高的点就被

19、逐渐侵蚀，并且工具的外形被复制到工件上。在加工过程中形成浓缩的金属小球由流动的电介质流体带走。当金属被完全侵蚀，工具就通过伺服控制进给机构向工件方向进给。Text&TranslationlEDM循环的每个脉冲维持了几个微妙的时间。按照每秒100 000次以上的频率重复的脉冲，使工件和电极材料侵蚀相同。随着工艺的发展，电极能通过向工件方向的伺服驱动来保持间隙距离为常数，直到最后的孔洞被加工出来。l电火花加工能用于所有导电材料而不管其硬度如何。该工艺最适合加工不规则形状的孔、槽和空腔。脆性工件能被加工而不会破裂。电火花加工可加工出各种形状的孔以及曲面上角度很小的孔，且不存在工具漂移的问题。Text

20、&Translationl目前，EDM广泛地应用于模具制造，特别是压力模具、挤压模具、锻模和铸模等。通过对图案复制的铣削加工得到的石墨电极被经常采用。lEDM最有利的是工具或模具能在它变硬后被加工，因此能得到极高的精度。烧结后的硬质合金工具能被加工，它取消了部分烧结时期的介质，因而也消除了孔、槽等诸如此类的加工误差。Text&Translationl电火花加工能高效地用于钻小的高纵横比的孔。20 mm厚的材料上直径为0.3 mm的孔或更厚材料都能容易地加工完成。带着高效冲洗，纵横比100:1的孔也能被加工出来。电火花加工已经成功地用于淬硬喷油嘴中的极小孔的加工。喷头周围具有精确形状的大量不同的

21、孔也能被加工出来。Complex Sentence Analysisl1 The tool is mounted on the chuck attached to the machine spindle whose motion is controlled by a servo-controlled feed drive.工具被安装在机床主轴的卡盘上，它的运动由伺服控制进给驱动。l whose：引导定语从句，修饰tooll attached：过去分词做the chuck的后置定语Complex Sentence Analysisl2 The high-power pulsed output i

22、s then applied to the tools and workpiece to produce the sparks responsible for material removal.高功率脉冲输出到工具和工件中以产生可靠的电火花来去除材料。l (be)responsible for：为负责，是造成的原因，responsible for 做后置定语修饰sparksl 此句是一个被动的语态，主语为the high-power pulsed output，pulsed做定语修饰outputComplex Sentence Analysisl3 Tools of cemented carb

23、ide can be machined after final sintering,which eliminates the need for an intermediate partial sintering stage,thus eliminating the inaccuracies resulting from final sintering after holes,slots,and so on,are machined.烧结后的硬质合金工具能被加工，它消除了部分烧结时期的介质，因而也消除了孔、槽等诸如此类的加工误差。l which：引导定语从句，并在从句中做主语，修饰整个句子l r

24、esult from：由产生Key to ExerciseslI.Translationl1.电火花加工 l2.pulsating DC power supplyl3.绝缘液体介质l4.convert into l5.传统晶体整流器l6.a servo-controlled feed mechanisml7.不管不顾l8.fragile workpiecel9.石墨电极l10.efficient flushing Key to ExerciseslII.True or Falsel1.T l2.F l3.T l4.F l5.FKey to ExerciseslIII.Blank Filling

25、l1.microseconds l2.uniform erosion l3.servodrive l4.constant gap distance l5.hardness.l6.Fragile workpiecesKey to ExerciseslIV.Chinese to Englishl1.filled with a dielectric fluidl2.The high-power pulsed output is then applied to the tools and workpiecel3.by a servo-controlled feed mechanisml4.A great advantage of EDM is that the tool or die can be machined after it is hardened l5.The process has been used successfully to produce very-small-diameter holeslThe end!