外文翻译机床数控改造

外文翻译机床数控改造 外文资料翻译 机床数控改造 一、数控系统发展简史及趋势 1946年诞生了世界上第一台电子计算机，这表明人类创造了可增强和部分 代替脑力劳动的工具。它与人类在农业、工业社会中创造的那些只是增强体力劳 动的工具相比，起了质的飞跃，为人类进入信息社会奠定了基础。6年后，即在1952年，计算机技术应用到了机床上，在美国诞生了第一台数控机床。从此， 传统机床产生了质的变化。近半个世纪以来，数控系统经历了两个阶段和六代的 发展。 1.1、数控（NC）阶段（1952～1970年） 早期计算机的运算速度低，对当时的科学计算和数据处理影响还不大，但不 能适应机床实时控制的要求。人们不得不采用数字逻辑电路"搭"成一台机床专用计算机作为数控系统，被称为硬件连接数控（HARD-WIRED NC），简称为数控（NC）。随着元器件的发展，这个阶段历经了三代，即1952年的第一代--电子管；1959年的第二代--晶体管；1965年的第三代--小规模集成电路。 1.2、计算机数控（CNC）阶段（1970年～现在） 到1970年，通用小型计算机业已出现并成批生产。于是将它移植过来作为 数控系统的核心部件，从此进入了计算机数控（CNC）阶段（把计算机前面应有的"通用"两个字省略了）。到1971年，美国INTEL公司在世界上第一次将计算机的两个最核心的部件--运算器和控制器，采用大规模集成电路技术集成在一块 芯片上，称之为微处理器（MICROPROCESSOR），又可称为中央处理单元（简 称CPU）。 到1974年微处理器被应用于数控系统。这是因为小型计算机功能太强，控 制一台机床能力有富裕（故当时曾用于控制多台机床，称之为群控），不如采用 微处理器经济合理。而且当时的小型机可靠性也不理想。早期的微处理器速度和 功能虽还不够高，但可以通过多处理器结构来解决。由于微处理器是通用计算机 的核心部件，故仍称为计算机数控。 到了1990年，PC机（个人计算机，国内习惯称微机）的性能已发展到很高 的阶段，可以满足作为数控系统核心部件的要求。数控系统从此进入了基于PC的阶段。 总之，计算机数控阶段也经历了三代。即1970年的第四代--小型计算机；1974年的第五代--微处理器和1990年的第六代--基于PC（国外称为PC-BASED）。 1 外文资料翻译 还要指出的是，虽然国外早已改称为计算机数控（即CNC）了，而我国仍习惯称数控（NC）。所以我们日常讲的"数控"，实质上已是指"计算机数控"了。 1.3、数控未来发展的趋势 1.3.1 继续向开放式、基于PC的第六代方向发展 基于PC所具有的开放性、低成本、高可靠性、软硬件资源丰富等特点，更 多的数控系统生产厂家会走上这条道路。至少采用PC机作为它的前端机，来处理人机界面、编程、联网通信等问 题 快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题 ，由原有的系统承担数控的任务。PC机所 具有的友好的人机界面，将普及到所有的数控系统。远程通讯，远程诊断和维修 将更加普遍。 1.3.2向高速化和高精度化发展 这是适应机床向高速和高精度方向发展的需要。 1.3.3向智能化方向发展 随着人工智能在计算机领域的不断渗透和发展，数控系统的智能化程度将不 断提高。 （1）应用自适应控制技术 数控系统能检测过程中一些重要信息，并自动调整系统的有关参数，达到改 进系统运行状态的目的。 （2）引入专家系统指导加工 将熟练工人和专家的经验，加工的一般规律和特殊规律存入系统中，以工艺 参数数据库为支撑，建立具有人工智能的专家系统。 （3）引入故障诊断专家系统 （4）智能化数字伺服驱动装置 可以通过自动识别负载，而自动调整参数，使驱动系统获得最佳的运行。 二、机床数控化改造的必要性 2.1、微观看改造的必要性 从微观上看，数控机床比传统机床有以下突出的优越性，而且这些优越性均 来自数控系统所包含的计算机的威力。 2.1.1 可以加工出传统机床加工不出来的曲线、曲面等复杂的零件。 由于计算机有高超的运算能力，可以瞬时准确地计算出每个坐标轴瞬时应该 运动的运动量，因此可以复合成复杂的曲线或曲面。 2.1.2 可以实现加工的自动化，而且是柔性自动化，从而效率可比传统机床 2 外文资料翻译 提高3～7倍。 由于计算机有记忆和存储能力，可以将输入的程序记住和存储下来，然后按 程序规定的顺序自动去执行，从而实现自动化。数控机床只要更换一个程序，就 可实现另一工件加工的自动化，从而使单件和小批生产得以自动化，故被称为实 现了"柔性自动化"。 2.1.3 加工零件的精度高，尺寸分散度小，使装配容易，不再需要"修配"。 2.1.4 可实现多工序的集中，减少零件 在机床间的频繁搬运。 2.1.5 拥有自动报警、自动监控、自动补偿等多种自律功能，因而可实现长 时间无人看管加工。 2.1.6 由以上五条派生的好处。 如：降低了工人的劳动强度，节省了劳动力（一个人可以看管多台机床）， 减少了工装，缩短了新产品试制周期和生产周期，可对市场需求作出快速反应等 等。 以上这些优越性是前人想象不到的，是一个极为重大的突破。此外，机床数 控化还是推行FMC（柔性制造单元）、FMS（柔性制造系统）以及CIMS（计算机集成制造系统）等企业信息化改造的基础。数控技术已经成为制造业自动化的 核心技术和基础技术。 2.2、宏观看改造的必要性 从宏观上看，工业发达国家的军、民机械工业，在70年代末、80年代初已开始大规模应用数控机床。其本质是，采用信息技术对传统产业（包括军、民机 械工业）进行技术改造。除在制造过程中采用数控机床、FMC、FMS外，还包括在产品开发中推行CAD、CAE、CAM、虚拟制造以及在生产管理中推行MIS（管理信息系统）、CIMS等等。以及在其生产的产品中增加信息技术，包括人 工智能等的含量。由于采用信息技术对国外军、民机械工业进行深入改造（称之 为信息化），最终使得他们的产品在国际军品和民品的市场上竞争力大为增强。 而我们在信息技术改造传统产业方面比发达国家约落后20年。如我国机床拥有量中，数控机床的比重（数控化率）到1995年只有1.9％，而日本在1994年已达20.8％，因此每年都有大量机电产品进口。这也就从宏观上说明了机床数控化 改造的必要性。 三、机床与生产线数控化改造的市场 3.1、机床数控化改造的市场 3 外文资料翻译 我国目前机床总量380余万台，而其中数控机床总数只有11.34万台，即我国机床数控化率不到3％。近10年来，我国数控机床年产量约为0.6～0.8万台，年产值约为18亿元。机床的年产量数控化率为6％。我国机床役龄10年以上的占60％以上；10年以下的机床中，自动/半自动机床不到20％，FMC/FMS等自动化生产线更屈指可数（美国和日本自动和半自动机床占60％以上）。可见我们的大多数制造行业和企业的生产、加工装备绝大数是传统的机床，而且半数以上 是役龄在10年以上的旧机床。用这种装备加工出来的产品普遍存在质量差、品 种少、档次低、成本高、供货期长，从而在国际、国内市场上缺乏竞争力，直接 影响一个企业的产品、市场、效益，影响企业的生存和发展。所以必须大力提高 机床的数控化率。 3.2、进口设备和生产线的数控化改造市场 我国自改革开放以来，很多企业从国外引进技术、设备和生产线进行技术改 造。据不完全统计，从1979～1988年10年间，全国引进技术改造项目就有18446项，大约165.8亿美元。 这些项目中，大部分项目为我国的经济建设发挥了应有的作用。但是有的引 进项目由于种种原因，设备或生产线不能正常运转，甚至瘫痪，使企业的效益受 到影响，严重的使企业陷入困境。一些设备、生产线从国外引进以后，有的消化 吸收不好，备件不全，维护不当，结果运转不良；有的引进时只注意引进设备、 仪器、生产线，忽视软件、工艺、管理等，造成项目不完整，设备潜力不能发挥； 有的甚至不能启动运行，没有发挥应有的作用；有的生产线的产品销路很好，但 是因为设备故障不能达产达标；有的因为能耗高、产品合格率低而造成亏损；有 的已引进较长时间，需要进行技术更新。种种原因使有的设备不仅没有创造财富， 反而消耗着财富。 这些不能使用的设备、生产线是个包袱，也是一批很大的存量资产，修好了 就是财富。只要找出主要的技术难点，解决关键技术问题，就可以最小的投资盘 活最大的存量资产，争取到最大的经济效益和社会效益。这也是一个极大的改造 市场。 四、数控化改造的内容及优缺 4.1、国外改造业的兴起 在美国、日本和德国等发达国家，它们的机床改造作为新的经济增长行业， 生意盎然，正处在黄金时代。由于机床以及技术的不断进步，机床改造是个"永 4 外文资料翻译 恒"的课题。我国的机床改造业，也从老的行业进入到以数控技术为主的新的行 业。在美国、日本、德国，用数控技术改造机床和生产线具有广阔的市场，已形 成了机床和生产线数控改造的新的行业。在美国，机床改造业称为机床再生 （Remanufacturing）业。从事再生业的著名公司有：Bertsche工程公司、ayton机床公司、Devlieg-Bullavd（得宝）服务集团、US设备公司等。美国得宝公司 已在中国开办公司。在日本，机床改造业称为机床改装（Retrofitting）业。从事改装业的著名公司有：大隈工程集团、岗三机械公司、千代田工机公司、野崎工 程公司、滨田工程公司、山本工程公司等。 4.2、数控化改造的内容 机床与生产线的数控化改造主要内容有以下几点： 其一是恢复原功能，对机床、生产线存在的故障部分进行诊断并恢复；其二 是NC化，在普通机床上加数显装置，或加数控系统，改造成NC机床、CNC机床；其三是翻新，为提高精度、效率和自动化程度，对机械、电气部分进行翻 新，对机械部分重新装配加工，恢复原精度；对其不满足生产要求的CNC系统以最新CNC进行更新；其四是技术更新或技术创新，为提高性能或档次，或为 了使用新工艺、新技术，在原有基础上进行较大规模的技术更新或技术创新，较 大幅度地提高水平和档次的更新改造。 4.3、数控化改造的优缺 4.3.1 减少投资额、交货期短 同购置新机床相比，一般可以节省60％～80％的费用，改造费用低。特别 是大型、特殊机床尤其明显。一般大型机床改造，只花新机床购置费用的1/3，交货期短。但有些特殊情况，如高速主轴、托盘自动交换装置的制作与安装过于 费工、费钱，往往改造成本提高2～3倍，与购置新机床相比，只能节省投资50％左右。 4.3.2 机械性能稳定可靠，结构受限 所利用的床身、立柱等基础件都是重而坚固的铸造构件，而不是那种焊接构 件，改造后的机床性能高、质量好，可以作为新设备继续使用多年。但是受到原 来机械结构的限制，不宜做突破性的改造。 4.3.3 熟悉了解设备、便于操作维修 购买新设备时，不了解新设备是否能满足其加工要求。改造则不然，可以精 确地计算出机床的加工能力；另外，由于多年使用，操作者对机床的特性早已了 5 外文资料翻译 解，在操作使用和维修方面 培训 焊锡培训资料ppt免费下载焊接培训教程 ppt 下载特设培训下载班长管理培训下载培训时间表下载 时间短，见效快。改造的机床一安装好，就可以 实现全负荷运转。 4.3.4 可充分利用现有的条件 可以充分利用现有地基，不必像购入新设备时那样需重新构筑地基。 4.3.5 可以采用最新的控制技术 可根据技术革新的发展速度，及时地提高生产设备的自动化水平和效率，提 高设备质量和档次，将旧机床改成当今水平的机床。 五、数控系统的选择 数控系统主要有三种类型，改造时，应根据具体情况进行选择。 5.1、步进电机拖动的开环系统 该系统的伺服驱动装置主要是步进电机、功率步进电机、电液脉冲马达等。 由数控系统送出的进给指令脉冲，经驱动电路控制和功率放大后，使步进电机转 动，通过齿轮副与滚珠丝杠副驱动执行部件。只要控制指令脉冲的数量、频率以 及通电顺序，便可控制执行部件运动的位移量、速度和运动方向。这种系统不需 要将所测得的实际位置和速度反馈到输入端，故称之为开环系统，该系统的位移 精度主要决定于步进电机的角位移精度，齿轮丝杠等传动元件的节距精度，所以 系统的位移精度较低。 该系统结构简单，调试维修方便，工作可靠，成本低，易改装成功。 5.2、异步电动机或直流电机拖动，光栅测量反馈的闭环数控系统 该系统与开环系统的区别是：由光栅、感应同步器等位置检测装置测得的实 际位置反馈信号，随时与给定值进行比较，将两者的差值放大和变换，驱动执行 机构，以给定的速度向着消除偏差的方向运动，直到给定位置与反馈的实际位置 的差值等于零为止。闭环进给系统在结构上比开环进给系统复杂，成本也高，对 环境室温要求严。设计和调试都比开环系统难。但是可以获得比开环进给系统更 高的精度，更快的速度，驱动功率更大的特性指标。可根据产品技术要求，决定 是否采用这种系统。 5.3、交/直流伺服电机拖动，编码器反馈的半闭环数控系统 半闭环系统检测元件安装在中间传动件上，间接测量执行部件的位置。它只 能补偿系统环路内部部分元件的误差，因此，它的精度比闭环系统的精度低，但 是它的结构与调试都较闭环系统简单。在将角位移检测元件与速度检测元件和伺 服电机作成一个整体时则无需考虑位置检测装置的安装问题。 6 外文资料翻译 当前生产数控系统的公司厂家比较多，国外著名公司的如德国SIEMENS公 司、日本FANUC公司；国内公司如中国珠峰公司、北京航天机床数控系统集团 公司、华中数控公司和沈阳高档数控国家工程研究中心。 选择数控系统时主要是根据数控改造后机床要达到的各种精度、驱动电机的 功率和用户的要求。 六、数控改造中主要机械部件改装探讨 一台新的数控机床，在设计上要达到：有高的静动态刚度；运动副之间的摩 擦系数小，传动无间隙；功率大；便于操作和维修。机床数控改造时应尽量达到 上述要求。不能认为将数控装置与普通机床连接在一起就达到了数控机床的要 求，还应对主要部件进行相应的改造使其达到一定的设计要求，才能获得预期的 改造目的。 6.1、滑动导轨副 对数控车床来说，导轨除应具有普通车床导向精度和工艺性外，还要有良好 的耐摩擦、磨损特性，并减少因摩擦阻力而致死区。同时要有足够的刚度，以减 少导轨变形对加工精度的影响，要有合理的导轨防护和润滑。 6.2、齿轮副 一般机床的齿轮主要集中在主轴箱和变速箱中。为了保证传动精度，数控机 床上使用的齿轮精度等级都比普通机床高。在结构上要能达到无间隙传动，因而 改造时，机床主要齿轮必须满足数控机床的要求，以保证机床加工精度。 6.3、滑动丝杠与滚珠丝杠 丝杠传动直接关系到传动链精度。丝杠的选用主要取决于加工件的精度要求 和拖动扭矩要求。被加工件精度要求不高时可采用滑动丝杠，但应检查原丝杠磨 损情况，如螺距误差及螺距累计误差以及相配螺母间隙。一般情况滑动丝杠应不 低于6级，螺母间隙过大则更换螺母。采用滑动丝杠相对滚珠丝杠价格较低，但 难以满足精度较高的零件加工。 滚珠丝杠摩擦损失小，效率高，其传动效率可在90%以上；精度高，寿命长； 启动力矩和运动时力矩相接近，可以降低电机启动力矩。因此可满足较高精度零 件加工要求。 6.4、安全防护 效率必须以安全为前提。在机床改造中要根据实际情况采取相应的措施，切 不可忽视。滚珠丝杠副是精密元件，工作时要严防灰尘特别是切屑及硬砂粒进入 7 外文资料翻译 滚道。在纵向丝杠上也可加整体铁板防护罩。大拖板与滑动导轨接触的两端面要 密封好，绝对防止硬质颗粒状的异物进入滑动面损伤导轨。 七、机床数控改造主要步骤 7.1、改造方案的确定 改造的可行性分析通过以后，就可以针对某台或某几台机床的现况确定改造 方案，一般包括： 7.1.1 机械修理与电气改造相结合 一般来说，需进行电气改造的机床，都需进行机械修理。要确定修理的要求、 范围、内容；也要确定因电气改造而需进行机械结构改造的要求、内容；还要确 定电气改造与机械修理、改造之间的交错时间要求。机械性能的完好是电气改造 成功的基础。 7.1.2 先易后难、先局部后全局 原系统的拆除必须对照原图纸，仔细进行，及时在图纸上作出标记，防止遗 漏或过拆(局部改造情况下)。在拆的过程中也会发现一些新系统设计中的欠缺之处，应及时补充与修正，拆下的系统及零件应分门别类，妥善保管，以备万一改 造不成功或局部失败时恢复使用。还有一定使用价值的，可作其他机床备件用。 切忌大手大脚，乱扔乱放。 7.2 合理安排新系统位置及布线 根据新系统设计图纸，合理进行新系统配置，包括箱体固定、面板安放、线 路走向和固定、调整元器件位置、密封及必要装饰等。连线工作必须分工明确， 有人复查检验，以确保连线工艺 规范 编程规范下载gsp规范下载钢格栅规范下载警徽规范下载建设厅规范下载 、线径合适、正确无误、可靠美观。 7.3 调试 调试必须按事先确定的步骤和要求进行。调试人员应头脑冷静，随时记录， 以便发现和解决问题。调试中首先试安全保护系统灵敏度，防止人身、设备事故 发生。调试现场必须清理干净，无多余物品；各运动坐标拖板处于全行程中心位 置；能空载试验的，先空载后加载；能模拟试验的，先模拟后实动；能手动的， 先手动后自动。 7.4、验收及后期工作 验收工作应聘请有关的人员共同参加，并按已制定的验收标准进行。改造的 后期工作也很重要，它有利于项目技术水平的提高和使设备尽早投产。验收及后 期工作包括： 8 外文资料翻译 7.4.1 机床机械性能验收 经过机械修理和改造以及全面保养，机床的各项机械性能应达到要求，几何 精度应在规定的范围内。 7.4.2 电气控制功能和控制精度验收 电气控制的各项功能必须达到动作正常，灵敏可靠。控制精度应用系统本身 的功能(如步进尺寸等)与标准计量器具(如激光干涉仪、坐标测量仪等)对照检查，达到精度范围之内。同时还应与改造前机床的各项功能和精度作出对比，获得量 化的指标差。 7.4.3 试件切削验收 可以参照国内外有关数控机床切削试件标准，在有资格的操作工、编程人员 配合下进行试切削。试件切削可验收机床刚度、切削力、噪声、运动轨迹、关联 动作等，一般不宜采用产品零件作试件使用。 7.4.4 图纸、资料验收 机床改造完后，应及时将图纸(包括原理图、配置图、接线图、梯形图等)、资料(包括各类说明书)、改造档案(包括改造前、后的各种记录)汇总、整理、移交入档。保持资料的完整、有效、连续，这对该设备的今后稳定运行是十分重要 的。 7.4.5 总结、提高 每次改造结束后应及时总结，既有利于提高技术人员的业务水平，也有利于 整个企业的技术进步。 八、数控改造几个实例 1、用SIEMENS 810M改造X53铣床 1998年，公司投入20万元，用德国西门子810M数控系统、611A交流伺服驱动系统对公司的一台型号为X53的铣床进行X、Y、Z三轴数控改造；保留了原有的主轴系统和冷却系统；改造的三轴在机械上采用了滚轴丝杆及齿轮传动机 构。整个改造工作包括机械设计、电气设计、PLC程序的编制与调试、机床大修， 最后是整机的安装和调试。铣床改造后，加工有效行程X/Y/Z轴分别为880/270/280 mm；最大速度X/Y/Z轴分别为5000/1500/800 mm/min；手动速度X/Y/Z轴分别为3000/1000/500 mm/min；机床加工精度达到?0.001mm。机床的三坐标联动可完成各种复杂曲线或曲面的加工。 2、用GSK980T和步进驱动系统改造C6140车床 9 外文资料翻译 1999年，公司投入了8万元，采用广州数控设备厂生产的GSK980T数控系统、DY3混合式步进驱动单元对公司的一台加长C6140车床的X、Z两轴进行改造；保留了原有的主轴系统和冷却系统；改造的两轴在机械上采用了滚轴丝杆 及同步带传动机构。整个改造工作包括机械设计、电气设计、机床大修及整机的 安装和调试。车床改造后，加工有效行程X/Z轴分别为390/1400 mm；最大速度X/Z轴分别为1200/3000 mm/min；手动速度为400mm/min；手动快速为X/Z轴分别为1200/3000 mm/min；机床最小移动单位为0.001mm。 3、用GSK980T和交流伺服驱动系统改造C6140车床 2000年，用广州数控设备厂生产的GSK980T数控系统、DA98交流伺服单元及4工位自动刀架对电机分厂的一台C6140车床X、Z两轴进行数控改造；保 留了原有的主轴系统和冷却系统；改造的两轴在机械上采用了滚轴丝杆及同步带 传动机构。整个改造工作包括机械设计、电气设计、机床大修及整机的安装和调 试。车床改造后，加工有效行程X/Z轴分别为390/730 mm；最大速度X/Z轴分别为1200/3000 mm/min；手动速度为400mm/min；手动快速为X/Z轴分别为1200/3000 mm/min；机床最小移动单位为0.001mm。 4、用SIEMENS 802S改造X53铣床 2000年，公司投入12万元，用德国西门子802S数控系统、步进驱动系统 对公司的另一台型号为X53的铣床进行X、Y、Z三轴数控改造；保留了原有的 主轴系统和冷却系统；改造的三轴在机械上采用了滚轴丝杆及齿轮传动机构。整 个改造工作包括机械设计、电气设计、机床大修，最后是整机的安装和调试。铣 床改造后，加工有效行程X/Y/Z轴分别为630/240/280 mm；最大速度X/Y/Z轴分别为3000/1000/600 mm/min；手动进给速度X/Y/Z轴分别为2000/800/500 mm/min；最小移动单位为0.001mm。 九、数控改造中的问题和建议 通过几台机床的数控改造工作后，发现工作中也存在许多问题，主要表现在： 一是各部门、开发人员职责不明朗，组织混乱，严重影响了改造进度； 二是制定的工作进程和 计划 项目进度计划表范例计划下载计划下载计划下载课程教学计划下载 大多只是凭经验制定，不太合理； 三是相关人员的培训工作没有到位，导致机床改造后工艺人员不会编程、操 作人员对机床操作不熟练等问题。 综合以上问题，有几点建议： 一是负责改造的员工职责明确，奖罚分明，充分调动员工的积极性； 10 外文资料翻译 二是培养一批高素质的应用和维护人员，选派人员外出进修，学习先进技术； 三是要注重用户使用、维护数控系统的技术培训，建立国内外数控技术资源 库。 Machine tool numerical control reforms First, CNC systems and the development trend of history 1946 birth of the world's first electronic computer, which shows that human beings created to enhance and replace some of the mental work tools. It and human agriculture, industrial society in the creation of those who merely increase compared to manual tools, from a qualitative leap for mankind's entry into the information society laid the foundation. Six years later, in 1952, computer technology applied to the machine in the United States was born first CNC machine tools. Since then, the traditional machine produced a qualitative change. Nearly half a century since the CNC system has experienced two phases and six generations of development. 1.1, Numerical Control (NC) phase (1952 to 1970) Early computer's computational speed low and the prevailing scientific computing and data processing is not affected, but can not meet the requirements of real-time control machine. People have to use digital logic circuit "tied" into a single machine as a dedicated computer numerical control system, known as the hardware connection NC (HARD-WIRED NC), called the Numerical Control (NC). With the development of components of this phase after three generations, that is, in 1952 the first generation - tube; 1959 of the second generation - transistor; 1965 of the third generation - small-scale integrated circuits. 1.2, Computer Numerical Control (CNC) phase (1970 to present) To 1970, GM has been a small computer and mass-produced. So it transplant system as the core component of NC, have entered a Computer Numerical Control (CNC) stage (in front of the computer should be "universal" word omitted). To 1971, the United States INTEL company in the world will be the first time the two most core computer components - computing and controller, a large-scale integrated circuit 11 外文资料翻译 technology integration in a chip, called the microprocessor (MICROPROCESSOR) , also known as the central processing unit (CPU). 1974 microprocessor to be used in CNC system. This is because the function of the computer is too small to control a machine tool capacity affluent (the time has been used to control more than one machine, called Group Control), as a reasonable economic use of the microprocessor. Minicomputer reliability and then not ideal. Early microprocessor speed and functionality while still not high enough, but can be adopted to solve the multi-processor architecture. As microprocessor core is a general computer components, it is still known as the CNC. By 1990, PC machines (personal computers, domestic habits that computer) performance has been developed to a high stage, as a CNC system to meet the requirements of the core components. NC system based on PC has now entered the stage. In short, CNC has also experienced a stage three generations. That is, in 1970's fourth generation - small computer; 1974 of the fifth generation - microprocessors and the sixth-generation 1990 - Based on the PC (called PC-BASED abroad). Also pointed out that, although the foreign computer has been renamed NC (CNC), but China still customary said Numerical Control (NC). Therefore, we stress the day-to-day "NC", in essence, is that "computer numerically controlled." 1.3, the trend of future development of NC 1.3.1 continue to open, the sixth generation of PC-based development Based on the PC with the open, low-cost, high reliability, rich in resources such as hardware and software features, and more CNC system manufacturers will embark on this path. At least it used PC as a front-end machine, to deal with the human-machine interface, programming, networking and communications problems, the former NC Some systems have the mandate. PC machine with the friendly interface, will be universal to all CNC system. Remote communications, remote diagnostics and maintenance will be more widespread. 1.3.2 high-speed and high-precision Development This is to adapt to high-speed and high-precision machine tools to the needs of the development direction. 12 外文资料翻译 1.3.3 intelligent direction to the development of With artificial intelligence in the computer field infiltration and the continuing development of the intelligent numerical control system will be continuously improved. （1）adaptive control technology CNC system can detect some important information in the process, and automatically adjust system parameters to improve the system running state purposes. （2）the introduction of expert guidance processing system Will be the experience of skilled workers and experts, processing and the general rules of law of special deposit system, the process parameters to the database as the foundation, and establish artificial intelligence expert system. （3）introduction of Fault Diagnosis Expert System （4）intelligent digital servo drives Automatic Identification can load, and automatically adjust parameters to get the best drive system operation. Second, CNC of the need for transformation 2.1, microscopic view of the necessity of From the micro perspective, CNC machine tools than traditional machines have the following prominent superiority, and these advantages are from the NC system includes computer power. 2.1.1 can be processed by conventional machining is not the curve, surface and other complex parts. Because computers are superb computing power can be accurately calculated instantaneous each coordinate axis movement exercise should be instantaneous, it can compound into complex curves and surfaces. 2.1.2 automated processing can be achieved, but also flexible automation to increase machine efficiency than traditional 3 to 7 times. Because computers are memory and storage capacity, can be imported and stored procedures remember down, and then click procedural requirements to implement the order automatically to achieve automation. CNC machine tool as a replacement procedures, we can achieve another workpiece machining automation, so 13 外文资料翻译 that single pieces and small batch production can be automated, it has been called "flexible automation." 2.1.3 high precision machining parts, the size dispersion of small, easy to assemble, no longer needed "repair." 2.1.4 processes can be realized more focused, in part to reduce the frequent removal machine. 2.1.5 have automatic alarm, automatic control, automatic compensation, and other self-regulatory functions, thus achieving long unattended processing. 2.1.6 derived from the benefits of more than five. Such as: reducing the labor intensity of the workers, save the labour force (one can look after more than one machine), a decrease of tooling, shorten Trial Production of a new product cycle and the production cycle, the market demand for quick response, and so on. These advantages are our predecessors did not expect, is a very major breakthrough. In addition, CNC machine tools or the FMC (Flexible Manufacturing Cell), FMS (flexible manufacturing system) and CIMS (Computer Integrated Manufacturing System), and other enterprises, the basis of information transformation. NC manufacturing automation technology has become the core technology and basic technology. 2.2, the macro view of the necessity of From a macro perspective, the military industrial developed countries, the machinery industry, in the late 1970s, early 1980s, has begun a large-scale application of CNC machine tools. Its essence is the use of information technology on the traditional industries (including the military, the Machinery Industry) for technological transformation. In addition to the manufacturing process used in CNC machine tools, FMC, FMS, but also included in the product development in the implementation of CAD, CAE, CAM, virtual manufacturing and production management in the implementation of the MIS (Management Information System), CIMS, and so on. And the products that they produce an increase in information technology, including artificial intelligence and other content. As the use of information technology to foreign forces, the depth of Machinery Industry (referred to 14 外文资料翻译 as information technology), and ultimately makes their products in the international military and civilian products on the market competitiveness of much stronger. And we in the information technology to transform traditional industries than about 20 years behind developed countries. Such as possession of machine tools in China, the proportion of CNC machine tools (CNC rate) in 1995 to only 1.9 percent, while Japan in 1994 reached 20.8 percent, every year a large number of imports of mechanical and electrical products. This also explains the macro CNC transformation of the need. Third, CNC machine tools and production lines of the transformation of the market 3.1, CNC transformation of the market My current machine total more than 380 million units, of which only the total number of CNC machine tool 113,400 Taiwan, or that China's CNC rate of less than 3 percent. Over the past 10 years, China's annual output of about 0.6 CNC machine tools to 0.8 million units, an annual output value of about 1.8 billion yuan. CNC machine tools annual rate of 6 per cent. China's machine tool easements over age 10 account for more than 60% below the 10 machines, automatic / semi-automatic machine less than 20 per cent, FMC / FMS, such as a handful more automated production line (the United States and Japan automatic and semi-automatic machine, 60 percent above). This shows that we the majority of manufacturing industries and enterprises of the production, processing equipment is the great majority of traditional machine tools, and more than half of military age is over 10 years old machine. Processing equipment used by the prevalence of poor quality products, less variety, low-grade, high cost, supply a long period, in view of the international and domestic markets, lack of competitiveness, and a direct impact on a company's products, markets, efficiency and impact The survival and development of enterprises. Therefore, we must vigorously raise the rate of CNC machine tools. 3.2, import equipment and production lines of the transformation of NC market Since China's reform and opening up, many foreign enterprises from the introduction of technology, equipment and production lines for technological transformation. According to incomplete statistics, from 1979 to 1988 10, the 15 外文资料翻译 introduction of technological transformation projects are 18,446, about 16.58 billion US dollars. These projects, the majority of projects in China's economic construction play a due role. Some, however, the introduction of projects due to various reasons, not equipment or normal operation of the production line, and even paralyzed, and the effectiveness of enterprises affected by serious enterprise is in trouble. Some of the equipment, production lines introduced from abroad, the digestion and absorption of some bad, spare parts incomplete, improper maintenance, poor operating results; only pay attention to the introduction of some imported the equipment, apparatus, production lines, ignore software, technology, and management, resulting in items integrity, and potential equipment can not play, but some can not even start running, did not play due role, but some production lines to sell the products very well, but not because of equipment failure production standards; because some high energy consumption, low pass rate products incur losses, but some have introduced a longer time, and the need for technological upgrading. Some of the causes of the equipment did not create wealth, but consumption of wealth. These can not use the equipment, production lines is a burden, but also a number of significant assets in stock, wealth is repaired. As long as identifying the main technical difficulties, and solve key technical problems, we can minimize the investment and make the most of their assets in stock, gain the greatest economic and social benefits. This is a great transformation of the market. Fourth, NC transformation of the content and gifted missing 4.1, the rise of foreign trade reform In the United States, Japan and Germany and other developed countries, and their machine transformation as new economic growth sector, the business scene, is in a golden age. The machine, as well as technology continues to progress, is a machine of the "eternal" issue. China's machine tool industry transformation, but also from old industries to enter the CNC technology mainly to the new industries. In the United States, Japan, Germany, with CNC machine tools and technological transformation of production lines vast market, has formed a CNC machine tools and production lines of the new industry. In the United States, transforming machine machine tool industry 16 外文资料翻译 as renewable (Remanufacturing) industry. Renewable industry in the famous companies: Bertsche engineering company, ayton machine tool company, Devlieg-Bullavd (Bo) services group, US equipment companies. Companies in the United States-run companies in China. In Japan, the machine tool industry transformation as machine modification (Retrofitting) industry. Conversion industry in the famous companies: Okuma engineering group, Kong 3 Machinery Company, Chiyoda Engineering Company, Nozaki engineering company, Hamada engineering companies, Yamamoto Engineering Company. 4.2, the content of NC Machine tools and production line NC transformation main contents of the following: One is the restoration of the original features of the machine tools, production line of the fault diagnosis and recovery; second NC, in the ordinary machine augend significant installations, or additions to NC system, transformed into NC machine tools, CNC machine tools; its Third, renovation, to improve accuracy, efficiency and the degree of automation, mechanical, electrical part of the renovation, re-assembly of mechanical parts processing, restore the original accuracy of their production requirements are not satisfied with the latest CNC CNC system update; Fourth, the technology updates or technical innovation, to enhance performance or grades, or for the use of new technology, new technologies, based on the original technology for large-scale update or technological innovation, and more significantly raise the level, and grades of upgrading. 4.3, NC transformation of the gifted missing 4.3.1 reduce the amount of investment, shorter delivery time Compared with the purchase of new machine, the general can save 60% to 80% of the costs and transforming low-cost. Especially for large, special machine tools particularly obvious. General transformation of large-scale machine, spent only the cost of the new machine purchase 1 / 3, short delivery time. But some special circumstances, such as high-speed spindle, automatic tray switching systems and the production of the installation costs too costly and often raise the cost of 2 to 3 times 17 外文资料翻译 compared with the purchase of new machine, only about 50 percent of savings investment. 4.3.2 stable and reliable mechanical properties, structure limited By the use of bed, column, and other basic items are heavy and solid casting components, rather than kind of welding components of the machine after the high-performance, quality, and can continue to use the new equipment for many years. But by the mechanical structure of the original restrictions, it is not appropriate to the transformation of a breakthrough. 4.3.3 become familiar with the equipment, ease of operation and maintenance The purchase of new equipment, new equipment do not know whether to meet the processing requirements. Transformation is not, can be used to calculate the machine processing capacity; In addition, since the use of many years, the operator of the machine has long been understood that in the operation, use and maintenance of the training time is short, quick. Transformation of the machine tools installed, we can achieve full load operation. 4.3.4 can take full advantage of the existing conditions Take full advantage of the existing foundation, not like buying new equipment as necessary to build a foundation. 4.3.5 can be used as control technology According to the development speed of technological innovation and in a timely manner increased level of automation in production equipment and efficiency, improve the quality of equipment and grades, and the old machine will be replaced by the current level of machine. 5, the choice of NC System NC system are the three major types of transformation, in accordance with specific circumstances Choose. 5.1, stepper motor drive the open-loop system The servo drive system is stepper motor, stepper motor power, such as electro-hydraulic pulse motor. NC system by sending commands to the progress of pulse, the drive control and power amplifier circuit, the stepper motor rotate through the gears with ball screw drive of the implementation of parts. As long as control commands the number of pulses, frequency and electricity sequence can control the 18 外文资料翻译 implementation of parts of the displacement movement, speed and direction of movement. Such a system does not require the test will be the actual position and velocity feedback to the input, so called open-loop system, the system accuracy of the displacement in the major decisions of the stepper motor angular displacement accuracy, transmission gear and other components of the leadscrew pitch accuracy, the accuracy of the lower displacement. The system is simple, convenient debugging maintenance, reliable, low cost, easy modification success. 5.2, or asynchronous motor DC Motor Drive, grating feedback loop measurement NC system And the open-loop system is the difference between a system: from the grating, such as position sensors for simultaneous detection device measured the actual position feedback signals, at any time and to compare the value will be the difference between the two enlarge and change, driven implementing agencies , given the speed of elimination of bias towards the direction of movement, until a given position feedback and the actual location of the margin of zero. Feed the closed-loop system in the structure than to the open-loop system into the complex, high-cost, strict requirements on the environment at room temperature. Design and debugging difficult than open-loop system. However, can be compared to the open-loop system into higher accuracy, faster speed, greater power drive characteristic indicators. Under the technological requirements and decide whether or not to adopt this system. 5.3, AC / DC servo motor drive, the semi-encoder feedback loop NC system Semi-closed-loop system detection devices installed in the middle of transmission, the implementation of indirect measurement components position. It can only be part of the internal loop compensation system components of the error and, therefore, it compared the accuracy of the closed-loop system of low accuracy, but its structure and debug than simple closed-loop system. Will be in the angular displacement detection devices and speed detection devices and make a servo motor when there was no need to consider the overall position of the installation of detection devices. NC system for the current production companies more manufacturers, such as the famous German company SIEMENS, Japan FANUC companies; Everest 19 外文资料翻译 domestic companies such as China, Beijing Aerospace CNC System Corporation, Shenyang and the central high-grade companies NC NC National Engineering Research Center. NC selection system is based mainly CNC machine modified to achieve the various precision, motor-driven power and user requirements. Sixth, the transformation of NC modification of the main mechanical components A new CNC machine tools in the design to achieve: a high static and dynamic stiffness of movement of the friction coefficient between small, transmission without clearance; big power; easy operation and maintenance. CNC transformation should be possible to achieve the above requirements. NC devices that can not be connected together with the general machine tools to reach the requirements of the NC machine tool, should also be major components corresponding to the transformation of up to a certain design requirements can be anticipated adaptation. 6.1, sliding Guideway On the NC lathe, in addition to a general guide lathes and precision of sexual orientation, but also a good Naimaca, wear characteristics, and reduce the frictional resistance to the death zone. At the same time there must be enough stiffness to reduce rail deformation on the impact of machining accuracy, a reasonable guide protection and lubrication. 6.2, deputy Gear General Machine concentrated in the main gear box and gearbox in the spindle. In order to ensure transmission accuracy, the use of CNC machine tool accuracy of gear higher grades than the general machine tools. In the structure must be able to achieve seamless transmission, thus transforming, machine main gear must meet the requirements of CNC machine tools, in order to ensure accuracy machining. 6.3, and the ball screw sliding leadscrew Screw-drive directly related to the transmission chain accuracy. Screw selection depends largely on the accuracy of the processing of requests and drag torque requirements. Accuracy is the main requirement of processing may be sliding Screw, but should check the leadscrew wear, such as pitch and pitch error accumulated error 20 外文资料翻译 and match Nut Gap. Sliding leadscrew general should not be less than six, the nut is too large gap replacement nut. The use of a sliding leadscrew relatively lower prices of ball screw, but it is difficult to meet the high precision machining. Ball screw friction losses small, high efficiency, the transmission efficiency of more than 90% of high accuracy, long life; starting torque and the torque of close campaigns, starting torque motor can be reduced. So to meet high precision machining requirements. 6.4, security Efficiency must be security as the prerequisite. Machine transformation in the light of the actual situation, we should take corresponding measures must not be ignored. Ball screw is sophisticated components, work to prevent dust particular chip and hard sand into the raceway. Screw in the vertical can also increase overall plate shields. And the extension units at both ends of the sliding contact surface Guide to seal well, absolutely rigid Coarse prevent the entry of foreign matter sliding surface damage Guide. 7, the main steps of CNC machine tools 7.1, for the determination of transformation Through analysis of the feasibility of transforming the future, we can against a Taiwan or a few machines determine the current status of reform programmes, which are generally include: 7.1.1 mechanical and electrical repair of combining Generally speaking, the need for a transformation of the electrical machine, are subject to mechanical repairs. Repairs to determine the requirements, scope, content must be decided by electrical machinery required to transform the structure of the request; transformation to determine electrical and mechanical repair, alteration between the staggered time requirements. The mechanical properties of intact electrical transform the basis of success. 7.1.2 easy first, and to the overall situation after the first local The removal of the original system must control the original drawings, carefully, to make drawings in a timely manner marked to prevent the demolition or omission (of local circumstances). In the process of demolition will discover some new system design in 21 外文资料翻译 the gaps, and that should be promptly added, removed and parts of the system should be disaggregated, safekeeping, in case of failure or partial failure reinstated. There is a definite value, and can be used for spare parts for other machines. Must not extravagantly used and misplaced. 7.2 reasonable arrangements for a new location and routing system Under the new system design drawings and reasonable new system configurations, including fixed box, panel installation, alignments, and the fixed position adjustment components, sealing and necessary, such as decoration. Connection must be a clear division of work, it was reviewed inspection to ensure connectivity of norms, diameter appropriate, accurate, reliable handsome. 7.3 Debugging Commissioning must be identified in advance by the steps and requirements. Debugging should be cool-headed, keep records, in order to identify and solve problems. Commissioning of the first test sensitivity security protection systems to prevent physical, equipment accidents. Debugging the scene must be cleaned, no superfluous items; coordinates extension units in the campaign centre of the whole trip; empty can test, first empty after loading; can simulate the test, after the first real dynamic simulation; can manually the upper hand After moving automatically. 7.4, acceptance and post-work Acceptance of the work to employ the staff to join, has been developed in accordance with the acceptance criteria. The transformation of the late work is also very important, it is conducive to enhancing the level of technical projects and equipment as soon as possible so that production. Acceptance and post include: 7.4.1 machine mechanical properties acceptance After mechanical repairs and maintenance as well as a full transformation, the mechanical properties of the machine tools should meet the requirement, in the geometric accuracy should be within the limits prescribed. 7.4.2 electrical control function and control accuracy acceptance Electrical control the various functions of action must be normal, sensitive and reliable. Application control accuracy of the system itself functions (such as stepping dimensions, etc.) and standard measurement apparatus (such as laser interferometer, 22 外文资料翻译 coordinate measurement machines) inspection, the scope of accuracy achieved. At the same time also and the transformation of the former machine tool accuracy of the various functions and to contrast, poor access to quantifiable indicators. 7.4.3 specimen cutting Acceptance Can refer to the CNC machine tool cutting at home and abroad specimen standards, qualified operatives, with the programming staff to test cutting. Acceptance specimen cutting machine stiffness can be cutting, noise, trajectory, and other related actions, the general should not be used for product components specimen use. 7.4.4 drawings, information acceptance Machine transformation of the latter should be timely drawings (including schematics, layout plans, wiring diagram, ladder diagram, etc.), information (including various brochures), the transformation of files (including the transformation before and after the various records) summary, collating, transfer to stall. Maintain data integrity, effective, continuous, and that the future stability of the equipment running is very important. 7.4.5 summing up, enhancing After the end of each should be promptly summed up, helps improve the operational level of technical personnel, but also conducive to the whole enterprise technical progress. 8, several examples of NC 1, use of X53 milling SIEMENS 810M 1998, the company invested 200,000 yuan, with Germany's Siemens 810 M CNC system, 611 A AC servo drive system for the company's X53 as a model of the milling machine for X, Y, Z three-axis NC transformation of the original reservation Spindle and cooling systems; transformation of the three-axis machine used in the roller screw and gear drive mechanism. Transformation of the entire work includes mechanical design, electrical design, PLC and the establishment of procedures for debugging, machine overhaul and, finally, the components are installed and debug. Milling After the transformation, processing effective itinerary X / Y / Z-axis respectively 880/270/280 mm; maximum speed X / Y / Z-axis respectively 5000/1500/800 mm / min; manual speed X / Y / Z-axis respectively 3000/1000/500 23 外文资料翻译 mm / min; machining accuracy of ? 0.001mm. Coordinate machine can be linked to complete all kinds of complex curves and surfaces processing. 2, and Step by GSK980T driven system of the C6140 Lathe 1999, the company invested 80,000 yuan, a Guangzhou NC plant production GSK980T NC system, DY3 hybrid stepping drive unit for the company's C6140 longer a lathe X and Z axes to transform the two retention The main axis of the original system and the cooling system; transformation of the two-axis machine used in the roller screw and belt drive mechanism. Transformation of the entire work includes mechanical design, electrical design, machine overhaul and the components are installed and debug. Lathe After the transformation, processing effective itinerary X / Z-axis respectively 390/1400 mm; maximum speed X / Z-axis respectively 1200/3000 mm / min; manual speed of 400 mm / min; manual for the rapid X / Z-axis respectively for the 1200/3000 mm / min; machine smallest mobile units of 0.001 mm. 3, and GSK980T with AC servo drive system of the C6140 Lathe 2000, NC plant in Guangzhou with production GSK980T NC system, DA98 AC servo unit and 4-position automatic tool carrier of a motor factory lathe C6140-X, Z two-axis NC transformation of the original reservation the spindle and cooling systems; transformation of the two-axis machine used in the roller screw and belt drive mechanism. Transformation of the entire work includes mechanical design, electrical design, machine overhaul and the components are installed and debug. Lathe After the transformation, processing effective itinerary X / Z-axis respectively 390/730 mm; maximum speed X / Z-axis respectively 1200/3000 mm / min; manual speed of 400 mm / min; manual for the rapid X / Z-axis respectively for the 1200/3000 mm / min; machine smallest mobile units of 0.001 mm. 4, use of X53 milling SIEMENS 802S 2000, the company invested 120,000 yuan, with Germany's Siemens 802 S CNC system, stepping drive system for the company's another model of the X53 milling machine for X, Y, Z three-axis NC transformation of the original reservation Spindle and cooling systems; transformation of the three-axis machine used in the roller screw and gear drive mechanism. Transformation of the entire work includes mechanical 24 外文资料翻译 design, electrical design, machine overhaul and, finally, the components are installed and debugged . Milling After the transformation, processing effective itinerary X / Y / Z-axis respectively 630/240/280mm; maximum speed X / Y / Z-axis respectively 3000/1000/600mm / min; manual feed rate X / Y / Z-axis respectively 2000/800/500mm / min; smallest mobile units of 0.001mm. 9, NC transformation of the issues and recommendations Through several of CNC machine work, there are also found in many of the issues, as demonstrated by: First, departments, staff development duties uncertainty, organizational chaos, seriously affecting the progress of reform; Second, the work of the development process and the development plan are mostly use their experience, not reasonable; Third, the training of relevant personnel not in place, resulting in improved process machine will be no programming, the operator of the machine operator unskilled, and other issues. Based on the above issues, a few suggestions: First, the staff responsible for the transformation of clear responsibilities, reward and punishment clear, and fully mobilize the enthusiasm of the staff; Second, cultivate a number of high-quality applications and maintenance personnel, selected staff on education and learn advanced technology; Third, we need to pay attention to users, maintaining CNC system technical training, the establishment of the technical resources at home and abroad NC. 电火花加工法对加工超韧性的导电 材料 关于××同志的政审材料调查表环保先进个人材料国家普通话测试材料农民专业合作社注销四查四问剖析材料 （如新的太空合金）特别有价值。这些金属很难 用常规方法加工，用常规的切削刀具不可能加工极其复杂的形状，电火花加工使之变得相对 简单了。在金属切削工业中，这种加工方法正不断寻找新的应用领域。塑料工业已广泛使用 25 外文资料翻译 这种方法，如在钢制模具上加工几乎是任何形状的模腔。 电火花加工法是一种受控制的金属切削技术，它使用电火花切除（侵蚀）工件上的多余 金属，工件在切削后的形状与刀具（电极）相反。切削刀具用导电材料（通常是碳）制造。 电极形状与所需型腔想匹配。工件与电极都浸在不导电的液体里，这种液体通常是轻润滑油。 它应当是点的不良导体或绝缘体。 用伺服机构是电极和工件间的保持0.0005~0.001英寸 （0.01~0.02mm）的间隙，以阻止他们相互接触。频率为20000Hz左右的低电压大电流的直流电加到电极上，这些电脉冲引起火花，跳过电极与工件的见的不导电的液体间隙。在火花 冲击的局部区域，产生了大量的热量，金属融化了，从工件表面喷出融化金属的小粒子。不 断循环着的不导电的液体，将侵蚀下来的金属粒子带走，同时也有助于驱散火花产生的热量。 在最近几年，电火花加工的主要进步是降低了它加工后的表面粗糙度。用低的金属切除 率时，表面粗糙度可达2—4vin.(0.05—0.10vin)。用高的金属切除率[如高达15in3/h(245.8cm3/h)]时，表面粗糙度为1000vin.(25vm)。 需要的表面粗糙度的类型，决定了能使用的安培数,电容,频率和电压值。快速切除金属（粗切削）时，用大电流,低频率,高电容和最小的间隙电压。缓慢切除金属（精切削）和需 获得高的表面光洁度时，用小电流,高频率,低电容和最高的间隙电压。 与常规机加工方法相比，电火花加工有许多优点。 1 . 不论硬度高低，只要是导电材料都能对其进行切削。对用常规方法极难切削的硬质 合金和超韧性的太空合金，电火化加工特别有价值。 2 . 工件可在淬火状态下加工，因克服了由淬火引起的变形问题。 3 . 很容易将断在工件中的丝锥和钻头除。 4 . 由于刀具（电极）从未与工件接触过，故工件中不会产生应力。 5 . 加工出的零件无毛刺。 6 . 薄而脆的工件很容易加工，且无毛刺。 7 . 对许多类型的工件，一般不需第二次精加工。 Electrical discharge machining Electrical discharge machining has proved especially valuable in the 26 外文资料翻译 machining of super-tough, electrically conductive materials such as the new space-age alloys. These metals would have been difficult to machine by conventional methods, but EDM has made it relatively simple to machine intricate shapes that would be impossible to produce with conventional cutting tools. This machining process is continually finding further applications in the metal-cutting industry. It is being used extensively in the plastic industry to produce cavities of almost any shape in the steel molds. Electrical discharge machining is a controlled metal removal technique whereby an electric spark is used to cut (erode) the workpiece, which takes a shape opposite to that of the cutting tool or electrode. The cutting tool (electrode) is made from electrically conductive material, usually carbon. The electrode, made to the shape of the cavity required, and the workpiece are both submerged in a dielectric fluid, which is generally a light lubricating oil. This dielectric fluid should be a nonconductor (or poor conductor) of electricity. A servo mechanism maintains a gap of about 0.0005 to 0.001 in. (0.01 to 0.02 mm) between the electrode and the work, preventing them from coming into contact with each other. A direct current of low voltage and high amperage is delivered to the electrode at the rate of approximately 20 000 hertz (Hz). These electrical energy impulses become sparks which jump the dielectric fluid. Intense heat is created in the localized area of the park impact, the metal melts and a small particle of molten metal is expelled from the surface of the workpiece . The dielectric fluid, which is constantly being circulated, carries away the eroded particles of metal and also assists in dissipating the heat caused by the spark. In the last few years, major advances have been made with regard to the surface finishes that can be produced. With the low metal removal rates, surface finishes of 2 to 4 um. (0.05 to 0.10um) are possible. With high metal removal rates finishes of 1 000uin. (25um) are produced. The type of finish required determines the number of amperes which can be used, the capacitance, frequency, and the voltage setting. For fast metal 27 外文资料翻译 removal (roughing cuts), high amperage, low frequency, high capacitance, and minimum gap voltage are required. For slow metal removal (finish cut) and good surface finish, low amperage, high frequency, low capacitance, and the highest gap voltage are required. Electrical discharge machining has many advantages over conventional machining processes. 1. Any material that is electrically conductive can be cut, regardless of its hardness. It is especially valuable for cemented carbides and the new supertough space-age alloys that are extremely difficult to cut by conventional means. 2. Work can be machined in a hardened state, thereby overcoming the deformation caused by the hardening process. 3. Broken taps or drills can readily be removed from workpieces. 4. It does not create stresses in the work material since the tool (electrode) never comes in contact with the work. 5. The process is burr-free. 6. Thin, fragile sections can be easily machined without deforming. 7. Secondary finishing operations are generally eliminated for many types of work. 28