《模具专业英语》教学课件—17Electric-Discharge-Machining.ppt

Lesson 17 Electric Discharge MachiningPPT模板下载： 行业PPT模板： 节日PPT模板： PPT素材下载： PPT图表下载： 优秀PPT下载： PPT教程： Word教程： Excel教程： 资料下载： PPT课件下载： 范文下载： 试卷下载： 教案下载： PPT论坛： TABLE OFCONTENT 1Passage2NewWordsandExpressions3Notes4ReadingMaterialLesson17ElectricDischargeMachining Metal removal in electric discharge machining (EDM) is due to metal erosion by interrupted electrical discharges. The process is carried out in a dielectric medium (generally kerosene). The EDM process is particularly advantageous in machining highly complicated shapes in forging, blanking, trimming, and other types of dies, and in machining hard and brittle materials. The major advantage of the process is that machining can be carried out in the hardened state of the work materials, thus eliminating heat treating and the possibility of subsequent cracking. 电火花加工利用断续的放电火花对金属的腐蚀作用来去除金属，该过程在一种绝缘介质（通常是煤油）中完成。

电火花加工在加工形状复杂的锻造、冲裁、挤压及其他类型模具和硬、脆材料时具有特殊优势其主要优点是可在工件材料的硬化状态下加工，因而消除了热处理的影响和产生开裂的可能性 Lesson17ElectricDischargeMachining1. Principle of EDM Machine The basic principle of the working of an EDM machine is shown in Figure 17-1. The main components of the machine are the worktable, tool holder, precision slides for tool holder in the two horizontal directions (X and Y), dielectric tank, pulse generating system, power supply and a filter for refining of used dielectric.1电火花加工机床的基本原理电火花加工机床的基本原理如图17-1所示，其重要组成部分是工作台、工具夹持器、使工具夹持器在两个水平方向（X、Y）上运动的精密滑台、介质箱、脉冲发生器、直流电源和净化介质的过滤器。

Figure17-1Schematicdiagramofelectricdischargemachining1filter;2pump;3electrolyte;4dielectrictank;5toolholder;6gearbox;7servomotor;8tool;9overflowlube;10workpiece;11worktable;12vibratorfortable图17-1电火花加工原理图1过滤器；2泵；3电解液；4介质箱；5工具夹持器；6传动箱；7伺服电动机；8工具；9溢出润滑油；10工件；11工作台；12振动台Lesson17ElectricDischargeMachining电源正极作为阳极，工具作为阴极最简单的电路由一个电容器和一个负载电阻组成（RC电路）由伺服电动机驱动使工具的末端靠近工件，当两者靠得很近时，介质不再绝缘，在工具和工件表面的最近点产生一次放电由于电容器放电和负载电阻的作用，工具和工件之间的电压下降，放电也就停止了这种突然的高强度的脉冲放电能产生很高的温度，且可能在电火花附近产生冲击波通常，与电火花接触的表面层被融化，并由于压力波和气蚀作用而被冲走，从而引起工具和工件表面的损耗。

The work is connected to the positive terminal (anode) and the tool is made the cathode. The simplest circuit consists of a condenser and charging resistance (RC circuit). The tool end is brought near the work piece surface by a servomotor. As the two get very near, the dielectric gives way and a discharge takes place between the nearest points on the tool and the work piece surfaces. The condenser discharges and because of the condenser discharges and the charging resistance, the voltage across the tool and the work piece drops, and hence the discharge also stops. This sudden pulse of high intensity discharge can give rise to very high temperatures and possibly shock waves in the vicinity of the park. The surface layer in line with the spark generally melts and is removed from the site by the pressure wave and cavitations. Thus both the tool and work piece surfaces wear out. Note句中的“take place”译为“发生，产生”。

Lesson17ElectricDischargeMachining2脉冲发生电路如果通过带或不带反馈的电子电路来产生脉冲，则可以克服与放电电路有关的一些缺点放电电路在高能级上工作，此时放电频率较低因为能级越高，消电离时间越长，拉弧危险越大；相反，脉冲电路可产生较高频率，在同样的去除速率下，每个电火花的能量就可降低因此，放电通道迅速消除电离，加工时间占循环时间的比值增大，带脉冲电路的机床少消耗能量1/31/2，工具损耗也有所降低 2. Relaxation Circuits If the pulses are generated by an electronic circuit with or without a feed back, some of the disadvantages associated with the relaxation circuit can be removed. Relaxation circuits operate at high energy levels with lower frequencies of sparks. This is because of higher energy levels, it takes more time for deionization and hence there is in greater danger of arcing. Pulse circuits, on the other hand, can have higher frequencies. For the same machining rate, a lower energy per spark would be needed. Hence the spark path gets deionized quickly and the ratio of machining time to cycle time increases. The pulse circuit machines consume two to three times less energy and also result in reduced tool wearing.Note句中的“be associated with.”是“与有关”的意思。

Lesson17ElectricDischargeMachining3. Tool Materials The major advantage of the EDM process is that tools of softer material can be used to erode very hard and brittle materials. The tool materials generally used are copper, brass, aluminum, graphite, etc. Silver-tungsten and copper-tungsten are low wearing tool materials which may be used for finished machining. Cast iron can also be used during rough machining. 3工具材料工具材料电火花加工的主要优点之一是可用较软的工具材料来加工硬、脆材料常用的工具材料是铜、黄铜、铝、石墨等银-钨合金和铜-钨合金是低损耗工具材料，可用于精加工，粗加工时可使用铸铁。

Lesson17ElectricDischargeMachining4. Applications The process can be used economically for the following applications on workpieces, which are good conductors of electricity:(1) For machining dies for forging, blanking, extrusion, etc.;(2) For drilling fine deep holes such as in fuel injector nozzles;(3) For machining hydraulic valve spools;(4) For slitting of hard alloys;(5) For manufacture of fragile components, which cannot be machined by conventional processes due to high tool forces.4应用应用电火花加工可经济地用于加工下列良好电导体的场合中：（1）用于加工锻造、冲裁、挤压模具等；（2）用于加工精细深孔，如燃料喷油器喷嘴；（3）用于加工液压阀阀体；（4）用于切割坚硬的合金；（5）用于加工易碎零件，这。