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1、Unit 8 Numerical ControlContentslNew Words&Expressions lText&TranslationlComplex Sentence AnalysislKey to ExercisesNew Words&Expressions lnumerical control 数字控制linstruction instrkn n.指令lbinary bainri adj.二进制llathe lei n.车床lmill mil v.铣ldrill dril v.钻lbore b:v.镗New Words&Expressions lgrind graind v.磨
2、lturret t:rit n.转盘lpunch pnt n.冲床lflame fleim n.(电)火花lwire-cutting 线切割lpipe bender 弯管机lspindle spindl n.主轴lcontour kntu n.轮廓New Words&Expressions lworkpiece w:kpi:s n.工件lcountersink kauntsik n.钻(沉头)孔lcounterbore n.镗(沉头)孔lream ri:m n.铰孔ltapping n.攻螺纹lspotwelding sptweldi 点焊lsynchronization sikrnaizei
3、n n.同步linterpolation int:pulein n.插补New Words&Expressions lparabolic prblik adj.抛物线的lcompensation kmpensein n.补偿lpertain p:tein v.合适lcoolant ku:lnt n.冷却液，切削液lclamping klmp n.夹紧lminiaturization minitraizein n.小型化ldedicated dedikeitid adj.专用的Text&Translationl 1Numerical control(NC)is a form of program
4、mable automation in which the processing equipment is controlled by means of numbers，letters，and other symbolsThe numbers，letters，and symbols are coded in an appropriate format to define a program of instructions for a particular workpart or job.The instructions are provided by either of the two bin
5、ary coded decimal systems:the Electronic Industries Association(EIA)code,or the American Standard Code for Information Interchange(ASCII).Text&TranslationlASCII-coded machine control units will not accept EIA coded instructions and vice versa.Increasingly,however,control units are being made to acce
6、pt instructions in either code.2Automation operation by NC is readily adaptable to the operation of all metalworking machines.Lathes,milling machines,drill presses,boring machines,grinding machines,turret punches,flame or wire-cutting and welding machines,and even pipe benders are available with num
7、erical controls.Text&Translationl1.Basic Components of NC lA numerical control system consists of the following three basic components：l(1)Program instructions.l(2)Machine control unit.l(3)Processing equipment.lThe program instructions are the detailed step by step commands that direct the processin
8、g equipment3In its most common form，the commands refer to positions of a machine tool spindle with respect to the worktable on which the part is fixedMore advanced instructions include selection of spindle speeds，cutting tools，and other functions.Text&TranslationlThe machine control unit(MCU)consist
9、s of the electronics and control hardware that reads and interprets the program of instructions and convert it into mechanical actions of the machine tool or other processing equipment lThe processing equipment is the component that performs metal processIn the most common example of numerical contr
10、ol，it is used to perform machining operations.The processing equipment consists of the worktable and spindle as well as the motors and controls needed to drive themText&Translationl2.Types of NC lThere are two basic types of numerical control systems：point to point and contouringlPoint to point cont
11、rol system,also called positioning,is simpler than contouring control systemIts primary purpose is to move a tool or workpiece from one programmed point to another.Usually the machine function，such as a drilling operation，is also activated at each point by command from the NC ProgramPoint to point s
12、ystem is suitable for hole machining operations such as drilling,countersinking，counterboring，reaming，boring and tapping.Hole punching machines，spotwelding machines，and assembly machines also use point to point NC systemText&TranslationlContouring system，also known as the continuous path system，posi
13、tioning and cutting operations are both along controlled paths but at different velocitiesBecause the tool cuts as it travels along a prescribed path，accurate control and synchronization of velocities and movements are importantThe contouring system is used on lathes，milling machines，grinders，weldin
14、g machinery，and machining centersMovement along the path，or interpolation，occurs incrementally，by one of several basic methodsText&Translationl4There are a number of interpolation schemes that have been developed to deal with the various problems that are encountered in generating a smooth continuou
15、s path with a contouring type NC systemThey include linear interpolation,circular interpolation,helical interpolation,parabolic interpolation and cubic interpolation.In all interpolations，the path controlled is that of the center of rotation of the toolCompensation for different tools，different diam
16、eter tools，or tools wear during machining，can be made in the NC programText&Translationl3.Programming for NC l5A program for numerical control consists of a sequence of directions that causes an NC machine to carry out a certain operation，machining being the most commonly used processProgramming for
17、 NC may be done by an internal programming department，on the shop floor，or purchased from an outside sourceAlso，programming may be done manually or with computer assistanceText&TranslationlThe program contains instructions and commandsGeometric instructions pertain to relative movements between the
18、tool and the workpiece.Processing instructions pertain to spindle speeds，feeds，tools，and so onTravel instructions pertain to the type of interpolation and slow or rapid movements of the tool or worktableSwitching commands pertain to on/off position for coolant supplies，spindle rotation，direction of
19、spindle rotation，tool changes，workpiece feeding，clamping，and so on.The first NC programming language was developed by MIT(Massachusetts Institute of Technology)developmental work on NC programming systems in the late 1950s and called APT(Automatically Programmed Tools).Text&Translationl4.DNC and CNC
20、 lThe development of numerical control was a significant achievement in batch and job shop manufacturing，from both a technological and a commercial viewpointThere have been two enhancements and extensions of NC technology，including：l(1)Direct numerical control l(2)Computer numerical control Text&Tra
21、nslationlDirect numerical control can be defined as a manufacturing system in which a number of machines are controlled by a computer through direct connection and in real timeThe tape reader is omitted in DNC，thus relieving the system of its least reliable componentInstead of using the tape reader，
22、the part program is transmitted to the machine tool directly from the computer memoryIn principle，one computer can be used to control more than 100 separate machines(One commercial DNC system during the l970s boasted a control capability of up to 256 machine tools.)The DNC computer is designed to pr
23、ovide instructions to each machine tool on demandWhen the machine needs control commands，they are communicated to it immediatelyText&TranslationlSince the introduction of DNC，there have been dramatic advances in computer technologyThe physical size and cost of a digital computer has been significant
24、ly reduced at the same time that its computational capabilities have been substantially increasedIn numerical control，the result of these advances has been that the large hard-wired MCUs of conventional NC have been replaced by control units based on the digital computerInitially，minicomputers were
25、utilized in the early 1970s As further miniaturization occurred in computers，minicomputers were replaced by todays microcomputersText&TranslationlComputer numerical control is an NC system using dedicated microcomputer as the machine control unitBecause a digital computer is used in both CNC and DNC
26、，it is appropriate to distinguish between the two types of systemThere are three principal differences：l(1)DNC computers distribute instructional data to，and collect data from，a large number of machinesCNC computers control only one machine，or a small number of machinesText&Translationl(2)DNC comput
27、ers occupy a location that is typically remote from the machines under their control.CNC computers are located very near their machine tools.l(3)DNC software is developed not only to control individual pieces of production equipment,but also to serve as part of a management information system in the
28、 manufacturing sector of the firm.CNC software is developed to augment the capabilities of a particular machine tool.Text&Translationl数字控制是一种利用程序实现自动控制的技术，加工制造设备采用数控技术后能由数字、字符和符号等进行控制。这些数字、字符和符号等被编码成按一定格式定义的指令程序，用于一个特定的加工或工件。这些指令可以采用两种二进制编码的数字系统中的任意一种进行定义，这两种二进制编码数字系统分别为电工协会代码(EIA)和美国标准信息交换代码(ASCII)
29、。一般来说，ASCII 编码的机床控制系统不能接受EIA 编码的指令，反之亦然。当然，这样的问题已经逐渐得到解决。数控加工制造目前已经广泛地应用于几乎所有的金属加工机床：车床，铣床，钻床，镗床，磨床，回转冲床，电火化，线切割和焊接机床，甚至弯管机也采用数控加工技术。Text&Translationl1.数控技术的基本组成 l一个数控系统主要由以下3个部分组成：l（1）程序指令。l（2）加工控制单元。l（3）制造装备。l程序指令是由一条一条的详细指令所组成，制造装备按要求执行这些指令，最常用的指令有：可以按要求使机床刀具主轴位于工作台上的具体位置，工作台是用于固定加工零件的，许多更高级的指令还包
30、括用于主轴速度的选择，刀具速度的选择及其他一些功能。Text&Translationl加工控制单元(MCU)包括一些用于阅读和解释程序指令并将其转换为机床刀具或其他制造装备的机械动作的电子和控制硬件。l制造装备是一种进行金属加工的数控技术装备，在常用的数控技术领域中，制造装备用于进行机械制造。制造装备包括工作台、主轴、电机及控制驱动单元。Text&Translationl2.数控技术的类型 l数控技术系统主要有两种类型：点对点数控系统和轮廓线数控系统。l点对点数控系统也称为位置数控系统，比轮廓线数控系统简单，其主要的原理是移动刀具或工件从一个程序控制点到另一个控制点，通常像钻床这样的加工功能，
31、每个点都可以通过NC 程序中的指令进行控制。点对点数控系统适用于像钻孔，沉孔加工、沉孔镗孔、铰孔和攻丝等。其他冲孔机床、点焊机和装配机床等也都采用点对点数控系统。Text&Translationl轮廓线数控系统也称为轮廓线路径数控系统，定位和切割操作都是以不同的速度沿着控制的路径进行的。由于刀具沿路径进行切削，因此刀具的运动和速度的精确控制和同步性能是非常重要的。轮廓线数控系统经常应用于车床、铣床、磨床、焊接机床和加工中心中。刀具沿着路径的运动，或称为插补逐渐出现了几个不同的方法。有许多类型的插补方法用于处理轮廓线数控系统中生成光滑的轮廓线时遇到的各种问题，几种比较常用的方法有线性插补，圆形插
32、补，螺旋形插补，抛物线插补和立方插补等，在所有的插补方法中，路经控制是以刀具的旋转中心为标准，对于不同类型，不同直径的刀具，加工过程中的不同刀具磨削量在数控程序中获得不同的补偿。Text&Translationl3.数控系统的编程 l一个数控系统(NC)的程序包括使数控(NC)机床进行操作和加工的一系列指令。数控程序可以由数控机床内部的程序库开发生成，也可以从外面采购获得。另外，程序可以通过手工编写，也可以进行计算机辅助编程。Text&Translationl数控程序包括一系列指令系统和命令系统。几何类指令用于定义刀具和工件之间的相对位置和运动；加工类指令用于定义主轴转速、进给、刀具转速等；传
33、送类指令用于定义刀具或工作台的运动速度和插补的类型等；开关类指令用于冷却液供给、主轴旋转、主轴旋转方向选择、换刀、工件进给、夹具等的开关。第一个用于数控编程的数控编程语言是20 世纪50 年代由麻省理工学院数控编程系统开发小组专家开发的，并被命名为自动编程工具(APT)。Text&Translationl4.直接数字控制(DNC)和计算机数字控制(CNC)l数控技术的发展在批量生产和车间生产加工中，不管是在技术上还是在商业上都获得了巨大的成功。目前，已经有两种数控技术系统得到了发展，分别为：l(1)直接数字控制(DNC)。l(2)计算机数字控制(CNC)。Text&Translationl直接
34、数字控制(DNC)可以被定义为这样一个生产制造系统，该制造系统有许多台加工机床，而相互之间由一台计算机采用直接连接，进行实时控制。这样，在传统的数字控制技术中采用的磁带阅读器在直接数字控制中被取消，从而保证了系统的可靠性，不使用磁带阅读器，被加工的零件程序就从计算机的存储器中直接传送到进行加工的刀具上。从原理上讲，一台计算机可以控制多达100 台加工机床，(在20 世纪70 年代一个商业使用的DNC 系统宣称可以控制多达256个机床刀具)。直接数字控制计算机用于按要求提供加工指令给每个进行加工的刀具上，当机床需要控制指令时，计算机就可以马上将指令传送到机床上。Text&Translationl
35、随着直接数字控制(DNC)技术和计算机技术的飞速发展，数字式计算机的尺寸和价格的大幅度的降低，数字式计算机的计算能力的大大提高，大量传统的以硬件线路为基础的加工控制单元被以数字计算机为基础的数字控制单元所替代。最初，在20 世纪70 年代使用了小型计算机。后来，随着计算机的进一步小型化，早期的小型计算机逐渐被现在的微型计算机所取代。Text&Translationl计算机数控(CNC)使用专用的微型计算机作为加工控制单元。因为数字计算机都用于计算机数控(CNC)和直接数控(DNC)，所以应该注意两者之间的区别，可以从3 个方面来加以区分:l(1)DNC 计算机是将指令数据发送到许多机床去和从许
36、多机床中收集数据，而CNC 计算机每次只控制一台或几台机床。l(2)DNC 计算机一般位于距机床一定距离的位置，而CNC 计算机一般都位于距机床较近的位置。l(3)DNC 计算机开发的软件不仅可以用于控制单件生产，而且可以用于一个企业的制造部门的管理信息系统，而CNC 计算机开发的软件一般只用于某个特殊加工的工具。Complex Sentence Analysisl1 Numerical control(NC)is a form of programmable automation in which the processing equipment is controlled by means
37、 of numbers，letters，and other symbols数字控制是一种利用程序实现自动控制的技术，加工制造设备采用数控技术后能由数字、字符和符号等进行控制。l a form of.：一个的形式l in which：引导的是定语从句，修饰前面的programmable automation l by means of：通过，使用方法Complex Sentence Analysisl2 Automation operation by NC is readily adaptable to the operation of all metalworking machines.Lat
38、hes,milling machines,drill presses,boring machines,grinding machines,turret punches,flame or wire-cutting and welding machines,and even pipe benders are available with numerical controls.数控加工制造目前已经广泛地应用于几乎所有的金属加工机床：车床、铣床、钻床、镗床、磨床、回转冲床、电火花，线切割和焊接机床，甚至弯管机也采用数控加工技术。l be adaptable to.：可适用于l available：有效
39、的，可获得的。该词的表现力很强，将其和另外的词搭配，能表达多种意思。例如：These data are readily available.这些资料易于得到。lThe doctor is available now.医生现在有空。Complex Sentence Analysisl3 In its most common form，the commands refer to positions of a machine tool spindle with respect to the worktable on which the part is fixed最常用的指令有：可以按要求使机床刀具主
40、轴位于工作台上的具体位置，工作台是用于固定加工零件的。l refer to：指涉及，指的是，适用于l with respect to：关于l on which：引导的是定语从句，修饰前面的worktable Complex Sentence Analysisl4 There are a number of interpolation schemes that have been developed to deal with the various problems that are encountered in generating a smooth continuous path with
41、a contouring type NC system.有许多类型的插补方法用于处理轮廓线数控系统中生成光滑的轮廓线时遇到的各种问题。l a number of：许多l 句中第一个that 引导的从句修饰前面的schemes，第二个that 引导的从句修饰前面的problems l deal with：处理，对待Complex Sentence Analysisl5 A program for numerical control consists of a sequence of directions that causes an NC machine to carry out a certa
42、in operation，machining being the most commonly used process一个数控系统(NC)的程序包括使数控(NC)机床进行操作和加工的一系列指令。l consist of：包含l that引导的从句修饰前面的directions l being 是一个分词，与machining一起构成独立主格结构Key to Exercisesl.Translate the following phrases into Chinese or English.1.数字控制2.program instructions3.加工控制单元4.machine control
43、 unit5.点对点数控系统6.processing equipment7.直接数字控制（DNC）8.interpolation schemes9.计算机数字控制（CNC）10.linear interpolationKey to Exercisesl.Mark the following statement with True(T)or False(F)according to the text.l1.Fl2.F l3.T l4.T l5.T Key to Exercisesl.Fill in the blanks with the suitable words or phrases giv
44、en below.l1.can be defined as l2.a number ofl3.Instead of l4.In principlel5.up tol6.is designed toKey to Exercisesl.Translate the Chinese parts given in the brackets into English.l1.a form of programmable automationl2.consists of the worktable and spindle as well as the motors and controls needed to drivel3.to move a tool or workpiece from one programmed point to anotherl4.its computational capabilities have been substantially increasedl5.pertain to relative movements between the tool and the workpiecelThe end!