模具专业英语课件-Unit_Four.ppt

1、Unit Four Manufacturing Technology of Mold,Passage One Numerical Control,Passage Two Electric Discharge Machining,Passage Three Wire Electrical Discharge Machining（Wire EDM）,Passage Four Rapid Prototyping and Manufacturing,Passage Five Electrochemical Machining（ECM）,Passage One Numerical Control,1,M

2、any types of machine tools and other industrial processes are equipped for numerical control， commonly called NC. The earliest forms of NC were developed in the 1950s when the movements of the axes of machine tools were assigned numerical values to facilitate the replacement of hand wheels and dials

3、 by control logic . NC requires accurate product design values; early systems were limited by the lack of detailed analyses for the geometrical drawings of the components to be manufactured. Later in the decade， this problem was overcome when computers were developed that could describe geometric to

4、ol movements as functions of a part -programming language. One of the best known of these early languages of tool instructions was APT （Automatically Programmed Tools）.,Unit Four Manufacturing Technology of Mold,Unit Four Manufacturing Technology of Mold,A significant development of the early 1960s

5、was a system known as Sketchpad， which enabled engineers to draw designs on a cathode -ray tube by using a light pen and a keyboard. When this system was connected to a computer， it enabled designers to study drawings interactively and facilitated the modification of their designs. A NC system or de

6、vice is one that controls the actions of a machine or process by the direct insertion of numerical data at some points， the system also must automatically interpret at least some portion of the data. Various kinds of numerical control systems use data coded in the form of numbers， letters， symbols，

7、words， or a combination of these forms.,Unit Four Manufacturing Technology of Mold,The instructions necessary for machining a part by NC are derived from the part drawing and are written in coded form on a program manuscript . The following kinds of data may be included on the manuscript: sequence o

8、f operation， kind of operation， depth of cut， coordinate dimensions for the center of the cutting tool， feed rate， spindle speed， tool number， and other miscellaneous operations. The coded information is punched into a ribbon of one -inch -wide machine -control tape with a tape -punching machine sim

9、ilar to a typewriter. The tape， usually made of paper or plastic， is inserted into the NC system， which is connected to the machine tool. The NC,Unit Four Manufacturing Technology of Mold,system interprets the information on the tape， thus activates relays and electrical circuits that cause the mach

10、ines servomechanisms and other controls to perform a sequence of operations automatically. On some NC systems， the coded information is inserted into the machines on punched cards or magnetic tape instead of punched tape. The tape can be stored for future use on the same machine or on others like it

11、 at any location. NC machines can produce parts accurately to tolerances of 0.0001 to 0.001 inch（0.0025 to 0.025 mm） depending on the design of the machine， the NC system， and other factors， such as environmental temperature. NC systems on machine tools can be classified into two basic types: point

12、-to -point（Fig.4 -1） and continuous -path （Fig.4 -2）. Point -to -point systems， commonly used on,Unit Four Manufacturing Technology of Mold,machines that perform hole -machining and straight -line milling operations， are relatively simple to program and do not require the aid of a computer.,Fig.4 -1

13、 Point -to -point Fig.4 -2 Continuous -path,Unit Four Manufacturing Technology of Mold,Continuous -path NC systems are commonly used on machines that perform contouring operations， such as milling machines， lathes， flame -cutting machines， and drafting machines . Program preparation for continuous -

14、path machines is more complex and usually requires the aid of a computer. An entire manufacturing technology known as CAD/CAM has developed around the NC concept and， in addition， CNC with its powerful microprocessors and other enabling technologies proffered from the personal computer has enabled t

15、he NC concept to branch into many variants， even a variant that is essentially record/playback. The latter of which are known in the industry as“teach lathes”. In addition， powerful and well -crafted human/machine,Unit Four Manufacturing Technology of Mold,interfaces allow the machine operator to pr

16、epare programs by means of interactive displays which request only the definition of the machining operation and its required parameters（such as a“pocket” and its dimensions） and not the actual tool paths with all the calculations that are required there. Anyone who knows machining concepts and blue

17、print interpretation can produce programs at the machine without the need for CAD/CAM. Nonetheless， the vast majority of programs are now produced with the aid of CAD/CAM and， for most users， CNC today（for all its gigahertz microprocessors and megabyte of real time kernel software） is conceptually l

18、ittle different from,Unit Four Manufacturing Technology of Mold,the first NC demonstrated by MIT in 1952. If there is a notable difference in concept， it is that CNC is no longer just for the spindle/cutting tool process of stock removal. It is for any processes that can be carried on machine tool m

19、otion platforms and that benefit from the separation of programming from operations， that is， from the CAD/CAM technology. These include lasing， welding， friction stir welding， ultrasonic welding， flame cutting， bending， spinning， pinning， gluing， fabric cutting， sewing， tape and fiber placement， ro

20、uting， picking and placing （ PnP）， sawing and undoubtedly， the industrial processes of tomorrow.,Unit Four Manufacturing Technology of Mold, Later in the decade， this problem was overcome when computers were developed that could describe geometric tool movements as functions of a part -programming l

21、anguage. 在稍后的十年内，当计算机的发展可以将几何刀具的运动描述成零件加工语言的函数时，这个问题就被解决了。 “that could describe geometric tool movements as functions of a part -programming language”作为定语从句修饰“developed”，“as functions of a part -programming language”在从句中作状语。 The tape can be stored for future use on the same machine or on others like

22、 it at any location. 打孔带能被储存以便将来在任何场所用在相同的机器或同它一样的其他机器上。,Notes:,Unit Four Manufacturing Technology of Mold,NC systems on machine tools can be classified into two basic types: point -to -point（Fig.4 -1） and continuous -path（Fig.4 -2）. 机床上的数控系统可分为两种基本类型:点到点型（图4 -1）和连续路径型（图4 -2）。 点到点型也称点位控制，从一个点位移到另一个点

23、位，它追求的结果是最终位置的准确性，并能在最终位置上保持，而并不重视两点之间的路径。 连续路径型也称轮廓控制，能够连续控制两个或两个以上坐标方向的联合运动。,New Words and Expressions ：,Unit Four Manufacturing Technology of Mold,machine tools机床 numerical control数字控制 axes ksi z n.轴 facilitatef siliteit vt.帮助 dial d i l n.刻度盘 control logic控制逻辑 geometrical drawing几何制图 instruction

24、in str k n n.指令 APT自动编程工具 sketchpad sket p d n.几何画板 cathode -ray阴极射线 interactively int r ktivli adv.交互式地,Unit Four Manufacturing Technology of Mold,interactively int r ktivli adv.交互式地 modification m difi kei n n.修改，修正 interpretin t prit v.解释 derivedi raiv vt.得自 manuscript m njuskript n.手稿，原稿 sequenc

25、e si kw ns n.顺序，次序 depth of cut切削深度 feed rate进给速度 spindle speed转速 miscellaneousmisi leinj s adj.混杂的 punch into打入 tape -punching machine打孔机 servomechanism s v u mek niz m n. 伺服机构,Unit Four Manufacturing Technology of Mold,punched card打孔卡片 magnetic tape磁带 tolerance t l r ns n.公差 environmentalin v i r

26、n mentl adj.环境的 point -to -point点到点 continuous -path连续路径 contouringk n tu ri n.造型 drafting machine绘图仪 complex k mpleks adj.复杂的 microprocessorm ikr u pr uses（r） n. 微处理器 phenomenonfi n min n n.现象 variant v ri nt n.变量 human/machine interface人/机交互界面,Unit Four Manufacturing Technology of Mold,definition

27、defi ni n n.定义 parameterp r mit n.参数 blueprint blu print n.设计图，蓝图 nonetheless n n les adv.虽然如此，但是 vastv st adj.巨大的，大量的 gigahertz i h ts n.千兆赫 megabyte me b it n.兆字节 kernel k nl n.核心，要点 demonstrate dem nstreit vt.示范 lasing leisi n.发射激光 welding weldi n.焊接 friction stir welding摩擦焊接,Unit Four Manufactur

28、ing Technology of Mold,ultrasonic welding超声波焊接 flame cutting气割 bending bendi n.弯曲 spinning spini n.旋压加工 pinning pini n.销连接，钉压 gluing lu i n.胶粘 fabric cutting帘布裁断 sewing s ui n.缝纫 routing ru ti n.造模铣切 picking and placing（PnP）分拣放置 sawing s i n.锯割,Exercises：,Answer the following questions according to

29、the text above. 1. What is the numerical control? Try to describe it using the words in this passage or of your own. 2. What kinds of data may be included on the program manuscript? 3. What are two basic types of numerically controlled machine tools? 4. Describe the processes that can be benefit fro

30、m the CAD/CAM technology.,Unit Four Manufacturing Technology of Mold,Translate the following words into Chinese: 1. machine tools 2. numerical control 3. control logic 4. geometrical drawing 5. Automatically Programmed Tools 6. depth of cut 7. feed rate 8. spindle speed 9. tape -punching machine 10.

31、 point -to -point 11. continuous -path 12. drafting machine,Unit Four Manufacturing Technology of Mold,Translate the passage below into Chinese: Numerical control has been in use for almost 40 years. Since its inception，it has been improved continually. Each improvement has added a new benefit or im

32、proved an existing benefit of NC as compared with traditional manual machine operation. During this period， a body of knowledge has developed from the actual benefits that can be derived from NC. There is a general consensus among manufacturing professionals that the principal benefits derived from

33、NC are the following:,Unit Four Manufacturing Technology of Mold,Unit Four Manufacturing Technology of Mold,Better planning Greater -flexibility Easier scheduling Less setup， lead，and processing time Better machine utilization Lower overall tooling costs Greater uniformity in cutting Greater accurac

34、y in cutting A higher degree of interchangeability of parts and tools More accurate cost estimates Permanent memory of how a part was made,参考译文：,数控技术,许多类型的机床及其他工业加工设备都配备有数字控制装置，通常称为NC。数控技 术的最早形式产生于19世纪50年代，那时机床主轴运动的数值化控制推动了用逻辑控制来替代的手轮和刻度盘的人工控制。数控技术需要正确的产品设计数值;先前的系统由于缺乏详细的制造零件几何制图的分析计算而受到限制。在稍后的十年内，当

35、计算机的发展可以将几何刀具的运动描述成零件加工语言的函数时，这个问题就被解决了。APT语言（自动编程工具）是早先最好的加工指令语言之一。,译,Unit Four Manufacturing Technology of Mold,Unit Four Manufacturing Technology of Mold,19世纪60年代初期，一个重要的发展是几何画板系统，这个系统能让工程师利用光笔和键盘在阴极射线管屏幕上设计图形。当这个系统被连接到计算机上时，能够使设计者交互式地学习制图且帮助他们做设计的修改。 数控系统或设备是一种通过在某些点上直接插入数字数据来控制机床或加工操作的 系统;系统也必须

36、能够自动地解释最基本部分的数据。不同类型的数字控制系统使用的数据指令多以数字、文字、符号、词组的形式或以几种形式的组合来实现。 数控加工零件必需的指令来自于部分的制图数据并且以编码的形式写在源程序上。 源程序上可能包括下列类型的数据:操作的顺序、操作的类型、切削深度、刀具中心的尺寸 坐标、进给速度、主轴转速、工具编号及其他各种的操作。,Unit Four Manufacturing Technology of Mold,代码信息被类似于打字机的打孔机打入一条一英寸宽的机器控制带上。打孔带通常由纸或塑料做成，被插入连接到机床的数控系统中。数控系统解释纸带上的信息，从而启动继电器，使机器的伺服机构

37、和其他控制机构的电路能自动地进行一系列的操作。在一些数控系统中，代码信息在代替了打孔带的打孔卡片或磁带上被插入到机器中。打孔带能被储存以便将来在任何场所用在相同的机器或同它一样的其他机器上。在机床设计、数控系统和其他的因素，如环境温度的允许下，数控机床能加工的零件的公差在0.00010.001 英寸（0.00250.025 mm）之间。 机床上的数控系统可分为两种基本类型:点到点型（图4 -1）和连续路径型（图4 -2）。点到点系统普遍应用于进行孔加工和直线铣削等的机床中，其相对编程简单且不需要计算机辅助。,Unit Four Manufacturing Technology of Mold,

38、图4 -1 点到点型 图4 -2 连续路径型,连续路径数控系统普遍应用于造型加工的机床，如铣床、车床、气割机和绘图仪等。连续路径加工的程序准备更复杂且通常需要计算机的辅助。,Unit Four Manufacturing Technology of Mold,一种称为CAD/CAM的完整的制造技术围绕着数控概念发展起来了。除此之外，由个 人计算机提供的有着强大的微处理器和其他促成技术的CNC（计算机数字控制）技术已经使数控观念产生了许多分支，一个分支本质上是一个记录或再生。后者在工业中被称为“教师车床”。 除此之外，强大的、工艺良好的人/机交互界面让机床操作员编写程序时只需知道机 床操作的定义

39、及其必需参数（例如一个“端口”及其尺寸），并不需要所有的真实刀具路径的计算。任何人只要知道加工概念和理解设计图就可以在机床上编写程序而不需要 CAD/CAM的辅助。虽然如此 ,现在绝大多数的程序还,Unit Four Manufacturing Technology of Mold,是需要借助于CAD/CAM来进行编 写的。对于大多数使用者来说，今天的CNC（尽管它有千兆赫微处理器和兆字节的实时核 心软件）与1952年麻省理工学院的第一台数控展示机床在概念上几乎没有什么不同。 如果在概念中有较大的不同的话，那就是 CNC不再只是适用于旋转/切削刀具对零件原料切除的加工。它能用于任何在机床刀具运

40、动平台上进行的加工，而且其另一优势是使编程从机器操作中分离开来，也就是来自CAD/CAM技术。这些技术包括发射激光、焊接、摩擦焊接、超声波焊接、气割、弯曲、旋压、钉压、胶粘、帘布裁断、缝合、带和光纤放置、 造模铣切、分拣放置（PnP）、锯割以及毫无疑问的未来工业加工方法。,Passage Two Electric Discharge Machining,2,Metal removal in electric discharge machining（EDM） is due to metal erosion by interrupted electrical discharges. The pro

41、cess 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 machini

42、ng can be carried out in the hardened state of the work materials， thus eliminating heat treating and the possibility of subsequent cracking.,Unit Four Manufacturing Technology of Mold,1.Principle of EDM machine,Unit Four Manufacturing Technology of Mold,The basic principle of the working of an EDM

43、machine is shown in Fig.4 -3. 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， a d.c. power supply and a filter for refining of used dielectric. The work is connec

44、ted to the positive terminal（ anode） and the tool is made the cathode . The simplest circuit con- sists of a condenser and charging resistance（ RC circuit）. The tool end is brought near the work piece surface by a ser-vomotor . As the two get very near， the dielectric gives way and a discharge takes

45、 place between the nearest points on the,Unit Four Manufacturing Technology of Mold,Fig.4 -3 Schematic diagram of electric discharge machining 1filter; 2pump; 3electrolyte; 4dielectric tank; 5tool holder; 6gear box; 7servomotor; 8tool; 9overflow lube;10workpiece;11table;12vibrator for table,Unit Fou

46、r Manufacturing Technology of Mold,tool and the work piece surfaces. The condenser discharges and because of 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 temp

47、eratures and possibly shock waves in the vicinity of the spark . 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.,2.Pulse Generation Circuit,Unit Four Manufacturing Techno

48、logy of Mold,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 with higher energy level

49、s， it takes more time for deionization and hence there is 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 cy

50、cle time increases. The pulse circuit machines consume two to three times less energy and also result in reduced tool wear.,Unit Four Manufacturing Technology of Mold,3.Tool Materials,The major advantage of the EDM process is that tools of softer material can be used to erode very hard and brittle m

51、aterials. 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 finish machining. Cast iron can also be used during rough machining.,4.Applications,The process can be used economicall

52、y for the following applications on workpieces， which are good conductors of electricity.,Unit Four Manufacturing Technology of Mold,（1）For machining dies for forging， blanking， extru- sion， etc.; （2）For drilling fine deep holes such as in fuel injector nozzles ; （3）For machining hydraulic valve spo

53、ols; （4）For slitting of hard alloys; （5） For manufacture of fragile components， which cannot be machined by conventional processes due to high tool forces.,5.Advantage of EDM,Electric discharge machining has many advantages over conventional machining processes:,Unit Four Manufacturing Technology of

54、 Mold,（1）Any material that is electrically conductive can be cut， regardless of its hardness. It is especially valuable for cemented carbides and the new super tough space -age alloys that are extremely difficult to cut by conventional means. （2）Workpiece can be machined in a hardened state， thereby

55、 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 c

56、an be easily machined with- out deforming .,Unit Four Manufacturing Technology of Mold,（7）Secondary finishing operations are generally elimi- nated for many types of work. （8）The process is automatic in that the servomechanism advances the electrode into the work as the metal is re- moved. （9）One pe

57、rson can operate several EDM machines at one time. （10） Intricate shapes， impossible to produce by conven- tional means， are cut out of a solid with relative ease. （11）Better dies and molds can be produced at lower costs. （12）A die punch can be used as the electrode to repro- duce its shape in the m

58、atching die plate， completed with the necessary clearance.,Unit Four Manufacturing Technology of Mold, 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. 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。 “take place”译为

59、“发生，产生”。 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. 如果通过带或不带反馈的电子电路来产生脉冲，可以克服与放电电路有关的一些缺点。 be associated with .是“与有关”的意思。 For manufacture of fragile components， which cannot be machined by conventional processes due to high tool forces. 用于加工易碎零件，这些零件因高应力而不能用传统方法加工。,Notes:,New Words and Expressions ：,Unit Four Manufacturing Technology of Mold,electric discharge machining（EDM）电火花加工 dischargedis t d n.放电，排放 erosioni r