计算机辅助设计与制造VIP

2009届本科毕业论文（设计）相关中英文翻译资料 资料题目：计算机辅助设计与制造 CAD and CAMThe engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes. Today these lathes are used primarily in small shops where smaller quantities rather than large production runs are encountered. In the beginning, CAD systems were no more than a graphics editor with some built-in design symbols. The geometry available to the user was limited to lines, circular arcs, and the combination of them. The development of free-form curves and surfaces, such as Coons patch, Beziers patch, and B-spline, enables a CAD systems allow a designer to move into the third dimension. Because a three-dimensional model contains enough information for NC cutter-path programming, the linkage between CAD and NC can be developed. So called turnkey CAD/CAM systems were developed based on this concept and became popular in the 1970s and 1980s. The 1970s marked the beginning of a new era in CAD the invention of three-dimensional solid modeling. In the past, three-dimensional, wire-frame models represented an object only by its bounding edges. They are ambiguous in the sense that several interpretations might be possible for a single model. There is also no way to find the volumetric information of a model. Solid models contain complete information; therefore, not only can they be used to produce engineering drawing, but engineering analysis can be performed on the same model as well. Later, many commercial systems and research systems were developed. Quite a few of these systems were based on the PADL and BUILD systems. Although they are powerful in representation, many deficiencies still exist. For example, such systems have extreme computation and resource (memory) requirements, an unconventional way of modeling objects and a lack of tolerance capability have all hindered CAD applications. It was not until the mid-1980s that solid modelers made their way into the design environment. Today, their use is as common as drafting and wire-frame model application.CAD implementations on personal computers (PCs) have brought CAD to the masses. This development has made CAD available and affordable. CAD originally was a tool used only by aerospace and other major industrial corporation. The introduction of PC CAD packages, such as AutoCAD, VersaCAD, CADKEY systems, made small companies, even individuals, own and use CAD. By 1988, more than 100,000 PC CAD Packages had been sold. Today, PC-based solid modelers are available and are becoming increasingly popular. Because rapid developments in microcomputers have enabled PCs to carry the heavy computational load necessary for solid modeling, many solid graphics user interface (GUI) , CAD systems can be ported easily from one computer to another, most major CAD systems are able to run on a variety of platforms. There is little difference between mainframe, workstation, and PC-based CAD systems.When a design has frozen, manufacturing can begin. Computers have an important role to play in many aspects of production. Numerically controlled (NC) machine tools need a part program to define the components being made; computer techniques exist to assist, and in some cases virtually automate the generation of part programs. Modern shipbuilding fabricates structures from welded steel plates that are cut from a large steel sheet. Computer-controlled flame cutters are often used for this task and the computer is used to calculate the optimum layout of the components to minimize waste metal. Printed circuit board assembly can also be improved by computer methods. Quality is maintained by computer-controlled automatic test equipment that diagnoses faults in a particular board and rejects defective boards from the assembly line. Computers are used extensively to plot the artwork used to etch printed circuit boards and also to produce part programs for NC drilling machines.One of the most important manufacturing functions is stock and production control. If the original design is done on a computer, obtaining lists of material requirements is straightforward. Standard computer data processing methods are employed to organize the work flow and order components when required.Part geometry requires calculation of a large number of tool positions. Part programming software is usually incorporated into a family of CAM (Computer Aided Manufacturing) software. Some CAM software is associated with CAD (Computer Aided Design) software into CAD/CAM stations. Then the CAM software can use the CAD files as a source of data, which speeds up the programming process.Part programming software is user-friendly, meaning that the programmer does not have to know the computer programming language or its operating system. It uses screen menus to lead the user through the programming process. Data can be entered via the keyboard, the mouse, or the function keys. Experienced programmers can use built-in macro capabilities and advanced techniques such as a family of parts to become even more productive. Programming software has a dynamic graphics database to hold the actual machining sequences. These sequences can be viewed, edited, chained, or deleted. The programming can be accomplished whether single cuts or CNC machine canned cycle will be used. The software will also automatically calculate the proper feeds and speeds to be used during the machining, create a tooling list, and define the tool path.Programmers can use different layers to associate with each profile being created or to construct clamps and fixtures to get a complete picture of the part setup. The tool motion can be seen as it will occur at the machine.Using part programming software, the programmer can easily solve trigonometry problems to define an accurate tool path. When the program is done, the programmer can send it from the PC to the machine via a communication channel using built-in software with communications capability. Good part programming software is capable of:（1）Establishing the machining parameters and tooling for a particular machine or job.（2）Defining the geometry and tool path.（3）Code generation, enabling the programmer to use standard communications protocols or create his or her own.计算机辅助设计及制造在讲述CAD的基本原理之前，先说说它的简史是比较合适的。CAD是计算机时代的产品。它从早期的计算机绘图系统发展到现在的交互式计算机图形学。两个这样的系统包括：麻省理工学院的Sage Project及Sketchpad。Sage Project旨在开发CRT显示器及操作系统。Sketchpad是在 Sage Project下发展起来的。CRT显示和光笔输入用于与系统进行交互操作。CAD与初次出现的NC和APT（自动编程工具）碰巧同时问世。后来，XY绘图仪作为计算机绘图的标准拷贝输出装置使用。一个有趣的现象是XY绘图仪与NC钻床具有相同的基本结构，除啦绘图笔被NC机床上的主轴的刀具代替之外。开始，CAD系统仅仅是一个带有内置设计符号的绘图编辑器。供用户使用的几何元素只有直线、圆弧以及两者的组合。自由曲线及曲面的发展，如昆氏嵌面、贝赛尔嵌面以及B样条曲线，使得CAD可用于复杂曲线与曲面设计。三维CAD设计允许设计者进入三维设计空间。由于一个三维模型包含啦NC刀具路径编程所需要的足够信息，所以能够开发CAD与NC之间联系的系统。所谓交钥匙的CAD/CAM系统便是根据这一概念开发的，并从20世纪70年代至80年代流行起来。20世纪70年代末，三维实体建模的发明标志着CAD一个新时代的开始。过去的三维线框模型仅用其边界来表达一个物体。这在某种意义上是含糊的，一个简单的模型可能有几种解释。同时也无法获得一个模型的体积信息。实体模型包含完整的信息，因此，他们不仅可用于生成工程图，而且也可在同一模型上完成工程分析。后来，开发了许多商业系统和研究系统。这些系统中相当多的是基于PADL和BUICD系统。尽管他们在表达上是强有力的，但仍然存在许多缺陷。例如，这种系统要有极强的计算能力和内存需求，非常规的物体建模实体建模开始介入设计环境。今天实体建模的应用如同绘图和线框模型应用一样普遍。在个人计算机上，CAD已走向大众化。这种发展使CAD应用面广并且很经济。CAD原本作为一种工具仅被航空和其它主要工业企业使用。诸如AutoCAD，VersaCAD，CADKEY等个人机CAD软件包的引入，使小型公司乃至个人可以拥有并使用CAD系统。到1988年为止已销售10万个以上的PCCAD软件包。今天，基于个人计算机的迅速发展使得个人计算机的实体建模的PCCAD易于获得，并且销售变得更为普及。由于微型计算机的迅速发展使得个人计算机能够承受实体模型需要的大量计算负荷，所以如今许多实体模型在PC机上运行，并且作为平台已不成问题。随着标准图形用户界面的发展CAD系统可以很容易的从一台计算机向另一台计算机传送，大多数CAD系统都能够在不同的平台上运行。在大型计算机、工作站和基于个人计算机的CAD系统之间几乎没有区别。当设计确定之后，制造才能开始。计算机在生产的许多方面扮演者一个重要角色。数控机床需要一个零件程序来表达被加工零件；计算机技术起到辅助作用，在谋些情况下实质上是自动生产零件加工程序。现代造船是用从大张钢板上切下并焊接钢板来制造船体结构的。计算机