CAD-And-CAM-计算机辅助设计(CAD)和计算机辅助制造(CAM)-外文翻译.doc-得力文库

1、CAD And CAMThe term CAD/CAM is a shortening of Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM). Well then, what is a general CAD system?The general CAD system was developed by considering a wide range of possible uses of such a system. The following were considered in detail:(1) M

2、echanical engineering design;(2) Building design;(3) Structural engineering design;(4) Electronic circuit design;(5) Animation and graphic design.It was postulated that four basic processes involving graphics occurred, to various degrees, in each field, namely:(1) Pure analysis - standard design and

3、 analysis processes.(2) Pure draughtingproduction of a drawing or picture by the manual creation and manipulation of lines, arcs, etc.(3) Drawing by analysisthe production of a picture or part of a picture directly from analysis: for example, production of cam profiles.(4) Analysis of drawingevaluat

4、ion of the properties of an item described graphically, for example the production of a quantity list by analysis of a builders plan drawing.For the system to be able to support pure analysis it must contain facilities for the running of analysis programs of unlimited length and for the storage and

5、rapid retrieval of large amounts of data.It was considered important that the user should be able to communicate directly and graphically with analysis programs. Graphics facilities were provided which were considered to be sufficient for a general design draughting system. However, the range of gra

6、phical construction techniques is so large in practice that the system contained only as many facilities as could practically be incorporated in the draughting system, leaving other more specialized techniques to be developed by the applications programmer.For both the production of drawing items by

7、 analysis and the analysis of drawings, it is essential that there is a simple efficient link between data produced by the draughting system and analysis programs. It is also essential that graphic data can be annotated in a way which is recognized by analysis programs but which does not affect the

8、draughting system.It was thought that for most practical application the general draughting system would be incorporated in a much larger specific applications system. For this reason the draughting system was as simple as possible consistent with reasonable running efficiency, so that it could be i

9、ncorporated into an applications system with the minimum of effort.The facilities embodied in the general CAD system are now described. These facilities are aimed at allowing a user to input graphical information into the computer and file it. Initial data entry is made by digitizing rough sketches.

10、 The system also permits the user to access the data, manipulate it, process it, output it in hard-copy form, or re-file it for permanent storage. There are many reasons for using CAD; the most potent driving force is competition. In order to win business, companies used CAD to produce better design

11、s more quickly and more cheaply than their competitors. Productivity is much improved by a CAD program enabling you to easily draw polygons, ellipses, multiple parallel lines and multiple parallel curves. Copy, rotate and mirror facilities are also very handy when drawing symmetrical parts. Many hat

12、ch patterns are supplied with CAD programs. Filling areas in various colors is a requirement in artwork and presentations. Different style fonts for text are always supplied with any CAD programs. The possibility of importing different graphic file formats and scanning of material (photographs) into

13、 a CAD program is also an asset especially as the image can be manipulated, retouched and animated.Another advantage of a CAD system is its ability to store entities, which are frequently used on drawings. Libraries of regularly used parts can be purchased separately or can be created by the draught

14、sman. For repetitive use on a drawing, a typical item may be retrieved and positioned in seconds, also oriented at any angle to suit particular circumstances.Using CAD products, assembly drawings can be constructed by inserting existing component drawings into the assembly drawing and positioning th

15、em as required.Clearance between different components can be measured directly from the drawing, and if required, additional components designed using the assembly as reference.CAD is very suitable for fast documentation. Previously, engineers and drafters wasted almost 30% of their time looking for

16、 drawings and other documents. Editing drawings to effect revisions and produce updated parts lists is quick and easy using a CAD product.When youre working on paper and a customer wants to change a drawing, you have to draw it all over again; In CAD, you make the change immediately and print out a

17、new drawing in minutes, or you can transmit it via E-mail or Internet all over the world instantly. On paper creating complex geometry often involves a lot of measuring and location of reference points; In CAD it is a breeze and revisions are even simpler. Many CAD programs include a macro or an add

18、-on programming language that allows customizing it.Customizing your CAD programs to suit your specific needs and implementing your ideas can make your CAD system different from your rivals. CAD can enable companies to produce better designs that are almost impossible to produce manually and to elim

19、inate dubious options during the conceptual design phase.Many CAD systems permit the rapid generation of models of proposed designs as wireframes. The solid modeling created in CAD can be transferred to a Finite Element Analysis (FEA) program, which will then verify whether the suggested design will

20、 be capable of supporting the expected loads.CAD will be linked to CAM (Computer Aided Manufacturing) whenever possible.CAD/CAM systems could produce computerized instructions for computerized machine controllers: lathes, mills, machining centers, turret punches, welding equipment, automated assembl

21、ies, etc.The CAM parts have evolved from the technology of Numerical Controlled (NC) machines. Early NC machines had their own on-board electronic control systems for their servo drives and motors, and where programmed by punched paper tape. In time, that becomes equivalent to a control stream of AS

22、CII text data typed into a text editor.Each machine maker developed their own control code scheme, usually a very cryptic set of letters for machine actions and numbers for the values of speed, depth, etc., and position coordinates.NC machines include a computer with a screen and keyboard. These use

23、 a “conventional” control language. Modern CAD/CAM systems automatically generate tool paths from a 3D model, and can simulate the cutting action on-screen. The most CAD/CAM systems are modular that means you can buy whichever modules do the option you want and they integrates into a unified system.

24、CIM (Computer Integrated Manufacturing) means complete integration of all aspects of manufacturing utilizing computerized information.CIM is the use of component data created by CAD in the CAM environment. In other words, the part geometry for manufacturing use in computerized form is used for NC pr

25、ogramming. This stage of development may be termed small-scale integration.The most highly developed form of CIM is the creation of a database containing all the information required for flexible manufacturing of components produced by the plant, in a form in which it can be retrieved and used by an

26、yone who needs it. Flexible manufacturing means the ability to make any components in small numbers or well as large, quickly, at economical cost, thus reducing tool charges, work in process and costly inventory.The main information flows involved in computer integrated manufacturing were clearly ou

27、tlined by Helberg. CAD generates product model and product describing data that are transformed by CAPP (computer aided process planning) into routings and control programs for the CAM systems. The PPC (production planning and control systems) systems generate and manage all operational data that ar

28、e used for controlling in the CAM area. CAQ (computer aided quality assurance) on a short-term basis corrects deviations in the manufacturing process and in the long run influences the development of products and methods with regard to quality assurance.Helbergs outline does not include further nece

29、ssary or desirable informational connections between the systems, such as a connection of CAD/CAPP and PPC for an accompanying calculation during design and routing generation, or feedback from manufacturing to planning. Furthermore, at least in the case of single-parts manufacturing, processes like

30、 design and process planning can be regarded as elements of the lead time of an order and therefore can be planned and controlled by the PPC system in the same way as the actual manufacturing and assembly processed. In that case a corresponding feedback becomes necessary.System integration and ratio

31、nalization is not simply a technological matter, as the CIM theorists suggest. To integrate disperse and incompatible systems we must change traditional procedure, not just throw in more money and equipment. Whenever we try to change procedures we find resistance. The larger the company and the more

32、 independent the network, the more difficult it is to turn policies and procedures around. Yet, as Fig. 21.1 suggests, a condition for successful system integration is that it extends along functional and support lines, in the global sense of the distributed environment.FUNCTIONAL(LINES OFPRODUCTS A

33、NDSERVICES)Fig. 21.1 System IntegrationFig. 21.1 System integration should be accomplished along three different axes of reference: distributed environment (topology), functional support, software and hardware.Because the tangible and intangible benefits of CIM are long term, the usual discounted-ca

34、sh-flow and return-on-investment methods cannot justify a CIM installation of a flexible manufacturing process frequently. Instead, strategic advantages and intangible benefits must be used to weigh the desirability of investment in CIM.CAD And CAM术语CAD/CAM是计算机辅助设计(CAD)和计算机辅助制造(CAM)的缩写。那么，什么是一个通用的CA

35、D系统呢？通用的CAD系统在被开发时要考虑这个系统应该具有尽可能广的应用范围，有以下几个方面详细考虑：（1）机械工程设计；（2）建筑设计；（3）结构工程设计；（4）电子电路设计；（5）动画和图形设计；在各个领域，包括作图在内都应该具有4个基本过程，无论其应用程度如何，即：纯分析标准设计和分析过程；（1）纯绘图用手工画线、圆弧等绘出的图或画；（2）图分析生产的一幅图画或者直接从分析:例如,生产的凸轮型材;（4）分析作图直接分析的方法产生描述的一个项目进行特性评估，比如通过对建筑师规划图的分析，得出这个项目的工程量表。对于能支持纯分析的系统，必须提供能运行无限长分析的程序以及存储和

36、快速检索大量数据的工具。人们看重的一点是，用户能通过直接和图形方式与分析程序通信。提供给通用绘图设计系统的作图工具应该充足。然而由于实际的制图技术范围太广，作图系统只能尽可能多的将实用工具包含进去，而将其他更专门的技术留给应用程序员去开发。对于有分析产生的作图项目和绘图分析而言，由作图系统所产生的数据和分析程序之间必须有一个简单高效的联系。另外，图形数据可用能被分析程序识别但不对组图系统产生影响的方法进行注释。对大多数实际应用来说，应考虑把通用作图系统合并到大型专用系统中。作图系统应该尽可能简单而高效地运行，这样把作图系统合并到应用系统就不用花很多的精力。现在说明通用CAD系统包含的工具，这些

37、工具的作用在于允许用户将图形信息输入计算机并归档。原始数据的输入通过将草图数字化而完成。该系统也允许用户存取、加工、处理并以硬拷贝形式输出这些数据，或者重新归档为永久性存储文件。使用CAD的原因有很多，最有效的动力就是竞争。为了赢得业务，公司使用CAD可以创造出更好的设计，并且在设计速度上比竞争对手更快，在成本上花费更少。通过使用CAD，成品率得到了很大提高，用户能够很容易地画多边形、椭圆、多条平行线和多条平行的曲线。在绘制对称部分时，复制、旋转、镜像这些工具使用起来也是很方便的。很多飞机舱口的样式就是用CAD程序设计的。用各种不同的颜色填充空白的区域是艺术和表达的需要。CAD总是提供许多不

38、同类型的字体。能够将不常用的图形文件格式和扫描材料（照片）导入CAD也是一大优点，特别是可以对图像进行加工、润饰和加入动画效果。CAD系统另外一个优点是能够存储在绘图中经常用到的实体。常用零件库可以另外购买或者由绘图员自己创建。在绘图中反复使用的一个典型的项目可以在数秒内检索并确定它的位置，也可定位在任一角度，以满足特定的要求。使用CAD产品，可以通过插入现有的零件图到装配图中，然后按照要求把他们放在合适的位置来绘制装配图。不同零件部件之间的间距能够在图中直接测量。如果需要，可以使用装配图设计出另外的零件作为参考。CAD非常适合文件的快速归档。以前，工程师和绘图员们浪费大约30%的时间去寻找图

39、纸和其它文档。用CAD产品可以快速而简便地编辑图样，对以前的东西进行修改，更新零件明细表。当你用纸绘图而客户希望修改图样的时候，你就得全部重画。使用CAD，你可以马上进行修改，并在几分钟之内打印出新图，或者通过E-mail和互联网立即传送到世界的各个地方。在纸上绘制复杂的几何图形时，经常要进行很多测量并且需要确定参考点。在CAD中，这是一个轻而易举的事情，修改也更容易了。许多CAD程序包含“宏”或者允许用户定制的附加程序语言。定制你的CAD系统来使它适合你的特定要求，并且它实现你的天才创意，从而能使你的CAD系统区别于你的竞争对手。CAD能够使企业完成更出色的设计，而用手工的方式几乎是不可能，

40、同时排出了概念设计阶段的不确定选项。许多CAD系统允许快速生成提出的设计模型作为一个线框模型。在CAD里创建的实体造型可以输入到一个有无限元分析（FEA）程序内，以检验设计方案能否承受预期的负荷。CAD总是尽可能地和CAM（计算机辅助制造）联系在一起。CAD/CAM系统能够为计算机化的电机控制器产生计算机指令。例如车床、磨床、加工中心、旋转冲天、焊接设备和自动化装置等。CAM是从数控机床技术中发展来的。早期的数控机床用于伺服驱动装置和电机的机载电子控制系统，编程要用穿孔纸袋，然后及时地变成等效的ASCII码文本数据控制流，输入到文本编辑器。每个设备制造商都开发自己的控制码方案，通常是一组用于表

41、示机械运动的秘密字符和表示速度、深度等和位置坐标的数值。数控机床包括一个带有屏幕和键盘的计算机。他们使用“常规”的控制语言。现代的CAD/CAM系统能够自动的从三维模型中产生刀具路径，并且能够在屏幕上模拟切削动作。大部分的CAD/CAM系统是模块化的，这就意味着你可以只购买你需要的模块并把他们集成为一个统一的系统。CIM（计算机集成制造）是指基于计算机化信息的制造业各方面的集成。CIM是CAD产生的零件数据在CAM环境中的应用。换句话说，就是将计算机化的零件加工成几何形状用于数控编程。这个发展阶段可以称作小规模集成。CIM开发的最高级模式是创建一个数据库，其中包含了工厂用于生产零件的柔性制造系

42、统需要的所有信息。在这种模式下，任何需要的人都可以检索和使用。柔性制造是指能够快速、经济地生产任意小批量或大批量的零件，从而减少加工费用、工作量并降低高昂的库存费用。计算机集成制造中的主要信息流程已经由Helberg清楚地概括出来。CAD生产产品模型以及产品描述数据，这些数据由CAPP（计算机辅助工艺规划）转换成工艺流程和CAM系统的控制程序。PPC系统（生产计划和控制系统）产生并管理所有在CAM中用于控制的操作数据。CAQ（计算机辅助质量保证）校正制造过程中的短期偏差，但从长远看则影响产品的开发和关于质量保证的办法。Helberg的信息流程没有包括系统之间必要的或者期望的更进一步的信息连接。

43、例如在设计和确定工艺流程时，伴随着计算机所进行的CAD/CAPP和PPC之间的连接，或者从制造到计划的反馈。此外，至少在加工单件零件的情况下，诸如在设计和工艺规划这样的规程可以认为是订单交付周期的一部分。因此，他们可以像实际加工和装配过程一样由PPC系统规划和控制。在这种情况下，相应的反馈就变得非常必要。CIM的理论专家们认为，系统集成化和合理化不是一个简单的技术方法问题。为了把分散的不兼容系统集成起来，不能只是简单地投入大量的经费和设备，而必须改变传统的工艺过程。但只要想改变工艺过程，就会遇到阻力。公司越大，网络就越独立，改变生产策略和工艺过程就越困难。正如图21.1所示，成功的系统集成条件实在分布式环境的全局上，沿功能轴和支持轴（硬件和软件）扩展。函数（线的产品与维修）分布式环境 (拓扑)硬件、主机、PC图.系统的集成因为使用CIM带来的切实利益在潜在的利益时长期，常用的折扣现金收支流和投资回报率的评价方法不能经常有效地评估一个安装了CIM的柔性制造系统。相反，必须用战略性优势和潜在的利益来估量对CIM投资的期望。

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