毕业论文（设计）外文翻译题目：
学院：机电工程学院
学生姓名：
专业：机械设计制造及其自动化
班级：
指导教师：赵晓栋
起止日期： 2010.11.15—2010.12.15
2010年11 月15日
Introduction to CAD/CAM and VP
1 Introduction to CAD/CAM
Throughout the history of our industrial society, many inventions have been patented and whole new technologies have evolved. Perhaps the single development that has impacted manufacturing more quickly and significantly than any previous technology is the digital computer. Computers are being used increasingly for both design and detailing of engineering components in the drawing office.
Computer-aided design (CAD) is defined as the application of computers and graphics software to aid or enhance the product design from conceptualization to documentation. CAD is most commonly associated with the use of an interactive computer graphics system, referred to as a CAD system. Computer-aided design systems are powerful tools and in the mechanical design and geometric modeling of products and components.
There are several good reasons for using a CAD system to support the engineering design function:
●To increase the productivity
●To improve the quality of the design
●To uniform design standards
●To create a manufacturing data base
●To eliminate inaccuracies caused by hand-copying of drawings and
inconsistency between drawings
Computer-aided manufacturing (CAM) is defined as the effective use computer technology in manufacturing planning and control. CAM is most closely associated with functions in manufacturing engineering, such as process and production planning, machining, scheduling, management, quality control, and numerical control (NC) part programming. Computer-aided design and computer-aided manufacturing are often combined CAD/CAM systems.
This combination allows the transfer of information from the design into the stage of planning for the manufacturing of a product, without the need to reenter the data on part geometry manually. The database developed during CAD is stored; then it is processed further, by CAM, into the necessary data and instructions for operating and controlling
production machinery, material-handling equipment, and automated testing and inspection for product quality.
1.1 Rationale for CAD/CAM
The rationale for CAD/CAM is similar to that used to justify any technology-based improvement in manufacturing. It grows our of a need to continually improve productivity, quality and competitiveness. There are also other reasons why a company might make a conversion from manual processes to CAD/CAM:
●Increased productivity
●Better quality
●Better communication
●Common database with manufacturing
●Reduced prototype construction casts
●Faster response to customers
1.2 CAD/CAM Hardware
The hardware part of a CAD/CAM system consists of the following component（1）one or mare design workstations, （2）digital computer, （3）plotters and other output devices, and（4）storage devices. The relationship among the component is illustrated in Fig. 10. 1. In addition, the CAD/CAM system would have a communication interface to permit transmission of data to and from other computer systems, thus enabling some of the benefits of computer integration.
The workstation is the interface between computer and user in the CAD system. The design of the CAD work station and its available features have an important influence on the convenience, productivity, and quality of the user output. The workstation must include a digital computer with a high-speed control processing unit (CPU). It contains require a and logic/arithmetic section for the system. The most widely used secondary storage medium in CAD/CAM is the hard disk, floppy diskette, or a combination of both.
The typical I/O devices used in a CAD system are shown in Fig. 10 .2. Input devices are generally used to transfer information from a human or storage medium to a computer where ¨CAD functions¨are carried out. There are two basic approaches to input an existing drawing: model the object on a drawing or digitize the drawing. The
standard output device for CAD/CAM is a CRT display. There are two major of CRT displays: random-scan-line-drawing displays and raster-scan displays. In addition to CRT, there are also plasma panel displays and liquid-crystal displays.
1.3 CAD/CAM Software
Software allows the human user to turn a hardware configuration into a powerful design and manufacturing system. CAD/CAM software falls into two broad categories, 2-D and 3-D, based on the number of dimensions are called 2-D representations of 3-D objects is inherently confusing. Equally problem has been the inability of manufacturing personnel to properly read and interpret complicated 2-D representations of objects. 3-D software permits the parts to be viewed with the 3-D planes-height, width, and depth-visible. The trend in CAD/CAM is toward 3-D representation of graphic images. Such representation approximate the actual shape and appearance of the object to be produced; therefore, they are easier to read and understand.
1.4 Applications of CAD/CAM
The emergence of CAD/CAM has had a major impact on manufacturing, by standardizing product development and by reducing design effort, tryout, and prototype work; it has made possible significantly reduced costs and improved productivity.
Some typical applications of CAN/CAM are as follows:
Programming for NC, C N C, and industrial robots;
Design of dies and molds for casting, in which, for example, shrinkage allowances are preprogrammed;
Design of tools and fixtures and E D M electrodes;
Quality control and inspection——for instance, coordinate-measuring machines programmed on a CAD/CAM workstation;
Process planning and scheduling.
AutoCAD is a computer-aided drafting and design system implemenented on a personal computer. It supports a large number of devices. Device drivers come with the system and include most of the digitizers, printer/plotters, video display boards, and plotters available on the market.
AutoCAD supports 2-D drafting and 3-D wire-frame models. The system is designed
as a single-user CAD package. The drawing elements are lines, poly-lines of any width, arcs, circles, faces, and solids. There are many ways to define a drawing element. For example, a circle can be defined by center and its radius, three points, and two end points of its diameter. The system always prompts the user for all options.
Of course, the prompt can be turned off by advanced users. Annotation and dimensioning are also supported. Text and dimension symbols can be placed on anywhere on the drawing, at any angle, and at any size. A variety of fonts and styles are also availble.
2Introduction to VP
2.1 Introduction
In an age when consumers demand high-quality, low-priced and customized products, the competition among ?rm s has ceased to bestrictly a price competition and is now a com-petition in product variety and speed to market (Pine, 1993). The current philosophy is to replace old products constantly with either an improved product or a new variation of the product. Differentiation in product variety, i.e. customization, assumes ever increasing importance as a marketing instrument. The duration of a product’s life depends on its acceptance by the consumers; a “failed” prod uct could be out of the market in a matter of months. A short product development cycle is crucial to the survival of the company as it enables the company to deliver new products to the market quickly. On the other hand, pursuing variety and quick response would not compromise the economy of scale, an advantage characterized by mass production. The balance between the economy of scale and scope is often difficult as manufacturers pursue a “dynamic stability” (Boynton and Bert, 1991).
Customization emphasizes the uniqueness of the products. This product proliferation naturally results in the continuous accretion of variety and thus engenders design variations and process changeovers. This situation contradicts the pursuit of the low costs of mass production where ?exibility is limited and stability is emphasized. Such a setup, therefore, presents product development with a special challenge. It is vital to provide designers with feedback from production, quality, and tests early at the conceptual stage so as to maintain the integrity of the product family and the continuity of the infrastructure, hence leveraging existing design and manufacturing investments.
Concurrent engineering (CE), as one approach to these problems, is well recognized with its natural focus on product design (Prasad, 1996). CE calls for the consideration and inclusion of product life cycle concerns such as aesthetics, ergonomics,
marketability, and manufacturability in the product design process. In CE implementation, the link between designs, represented as geometric information, and manufacturing instructions has been a major obstacle to CAD/CAM integration (Barash, 1985). A number of techniques have been developed to bridge this gap, including feature-based design and feature extraction approaches. Aiming at the challenge of keeping the economy of scale, this paper adopts an alternative approach, called design by manufacturing simulation (DM S). The concept that manufacturing simulation could be used as a design tool was ?rst introduced by Gossard (1975). In his approach, parts are designed by simulating manufacturing operations on the screen; thus, designers generate manufacturing speci?cations as they design. Simulation based design (SBD) is a similar approach popularized by successful DARPA (Defense Advanced Research Projects Agency) initiatives in the early 1990s (DARPA, 1994). SBD refers to the use of computer simulation techniques for system design using virtual proto-typing models. Simulation of virtual proto-type design is accomplished through the construction of a virtual system prototy peand virtual environments.
On the other hand, a number of marketing studies (Berkowitz, 1987; LaChance-Porter,1993; Sujan and Dekleva, 1987) have pointed out the s igni?cance of understanding cus tomer preferences on the appearances of new products. An attractive appearance draws customers to a product and adds value to the product by increasing the quality of the user’s experiences (Kotler and Rath, 1984).Therefore, identifying those elements that enhance t he chances for customer’s accep tance represents an important issue for engineering designers. With this in mind, effective use of customer preference data in engineering design helps integrate the perspectives of marketing professionals and designers.
As for a product’s appearance, customer reactions appear to depend in part on how well the design conforms to aesthetic principles such as those developed by Gestalt theorists (Veryzer, 1993) and ergonomics criteria. Preferences also may be affected by how well a new design ?ts within the constellation of existing designs. Therefore, the ease with which customers may categorize a new design and its closeness to existing proto-types may play a signi?cant role in market-place acceptance (Sujan and Dekleva, 1987).Although Gestalt and prototypicality principles may apply widely to customers, salient individual differences (i.e. customization) in product appearance preferences are possibly expected. As a result, it is important for design teams to explore the customer’s per ception on the appearance of a target product.
Traditionally, market analysis techniques are adopted to investigate customer responses to design options. For example, conjoint analysis is widely used to measure preferences for different product pro?les and to build market simulation models (Dobson and Kalish, 1993). It takes a qualitative approach and uses focus groups to provide a reality check on the usefulness of a new product design. However, although a number of researchers agree on the importance of including customer preferences and other marketplace information in product designs, methodologies to capture product
preferences and tastes are not evident in a concurrent engineering context (Veryzer, 1993). In other words, it is imperative to integ rate both the customer’s percep tion and manufacturing concerns in design evaluation.
2.1 Types of prototype
During product development, physical proto-types are frequently required for iterative evaluation to provide feedback for design modi?cation such as selection of design alter-natives, engineering analysis, manufacturing planning and visualization of a product. Even using conventional processes and highly skilled technic ians, the time, effort and cost of constructing a prototype are substantial (Gibson et al.,1993). Rapid Prototyping (RP) systems are capable of making highly accurate prototypes in a short time. The starting point for such systems is good quality 3D CAD modeling where solid models are constructed and then post-processed in a layer format, using, for instance, stereolithography,to make them suitable for the prototyping machines (Jacobs, 1992).
There are basically two types of virtual proto-type, i.e. the immersive virtual prototype and the analytical virtual prototype. Recent progress in the development of graphics hard-ware has allowed complex geometric representations to be rendered and manipulated in real time. These representations, when coupled with new human computer interfaces such as data gloves and headsets, can help give the user a belief that the object actually exists. The virtual effects and tactile proper-ties are of primary importance in these immersive virtual prototypes, which are necessary in visualizing and interacting with the digital clay. A more useful form of virtual prototype, in the context of product development, is one that tells the user how it will perform and behave in its intended environment. This analytical virtual prototype usually uses standard computing technology (mouse, keyboard and screen). It is thought that eventually they will also use immersive technology. Leaving aside the problems of moving toward immersive environments, analytical virtual prototypes will not be used efficiently within the product development process until geometric representations are efficiently integrated with analysis applications. This seems to be a serious problem.
CAD/CAM技术与虚拟样机技术概论
1 CAD/CAM技术概论
1.1 前言
遍及我们工业社会的历史，一些发明已经取得了很多专利，并且有了新的发展。比以前任何一项技术能对制造业产生更迅速，更重大影响的发展或许是数字化计算机。计算机被逐步的应用到图纸和零件的设计。
计算机辅助设计（CAD）是指从概念化的文件中辅助或提高产品设计的计算机应用和图形软件。CAD是与交互式计算机制图系统最普遍的结合，称之为CAD系统。计算机辅助设计系统是有效的工具，并在机械设计和产品元件的几何模型中得到应用。下面是CAD系统在图纸设计中的几个有利因素：
1）提高生产能力；
2）增加设计数量；
3）统计设计标准；
4）创建一个生产数据库；
5）减小由手工复制图纸而引起的偏差。
计算机辅助制造（CAD）是指在设计和控制制造业有效利用计算机技术。CAM与制造工程最亲密的结合，例如程序设计、生产设计、机械加工、调度、控制、质量控制和数字控制程序设定。计算机辅助设计和计算机制造经常被组合为CAD/CAM系统。
这个组合使信息传递从设计阶段进入到设计生产阶段，不用人工重复输入几何部分的数据。通过CAD存储数据，再利用CAM促进工艺过程的发展，进入到必须数据和指令过程，并通过控制生产设备，原料处理设备对产品质量进行自动测试和检验。
1.2 CAD/CAM的理论基础
CAD/CAM的理论基础与过去已被证明的任何制造工艺基础上的改进相类似。它带来不断提高生产率、质量和竞争力的必要。企业从手工发展转化为CAD/CAM还有一些其他因素：
1）提高生产力；
2）提高产品质量；
3）生产上有公共的数据库；
4）减少样板伍的成本；
5）更快的响应消费者。
1.3 CAD/CAM硬件
CAD/CAM系统的硬盘部分由以下元件组成：
1）一个或更多个设计工作站；
2）数字计算机；
3）绘图机、打印机和其他的输出设备；
4）CAD/CAM系统应该有传输接口，使之与别的计算机系统传输数据成为可能，因此，有益于使计算机成为整体。
CAD系统中工作站是计算机与其使用者的连接体。CAD工作站的结构和它的可利用的特点再使用的特点在使用者产品的适合度、生产率和质量上的影响。工作站必须一个图形显象终端设备和一个输出设备。应用CAD/CAM需要一个有高速中央处理机（CPU）的数字计算机。它包括主存储器和逻辑系统或算术系统。在CAD/CAM中最广泛的利用的二级存储器是硬盘、软盘或二者的结合。
输入装置通常被用来从操作者或存储器到计算机传输信息，这样就执行了“CAD的操作”。输出已有绘图有两个基本方法：绘图模型或将资料数字化绘图。
CAD/CAM的标准输出设备是一个阴极射线管显示器。阴极射线管主要有两种类型：随机扫描直线制图显示器和光栅扫描显示器。除此之外阴极射线管还包括等离子显示器和液晶显示器。
1.4 CAD/CAM软件
软件使用户从硬盘构形转向为高效的设计和生产系统。CAD/CAM软件分为两大类：根据完成的几何图的维数分为2-D和3-D。CAD的组件即代表物在2 维空间中则称之为2-D软件。早期系统被限制在2-D。这是一个严重的不足，因为2-D表示3-D目标是本质上的混淆。同样的问题是生产人员不能彻底的看懂并解释难懂的2-D表示目标。3-D软件使高、宽深度在三维空间中可见。CAD/CAM趋势是用3-D形象的表现物体。因此，这样的与实物接近的模型在生产时容易被理解。
2 虚拟样机技术概论
2.1 前言
在这个时代，当消费者越来越追求高品质，低价格和可定制产品时，公司之间的竞争已不再是传统的严格意义上的价格竞争，而是一种新型的在产品多样性和对市场快速反应方面的竞争了。目前大部分公司的理念主要是对已推出市场的老产品不断的进行改良，要么通过提升老产品的品质，要么对老产品做出一些新的变化。因此，在产品品种不断分化的现实情况下，“定制”，作为一种营销手段，其承担的任务的重要性必将日益凸显。然而，一种产品的生命期限往往主要依赖于它被消费者所接受的程度，一种“失败”的产品从上市到无人问津可能只需要一个月的时间。所以，产品开发周期的长短对该公司能否长期生存就显得得至关重要了。因此，这就要求公司从产品设计到向市场推出新产品必须做到非常迅速。另一方面，过分追求产品的多样化和对市场快速反应有时会产生一些负面影响，但其最大的优势和特点是其能够进行大规模的生产。经济规模和范围的平衡是很难把握的，因此，制造商往往很难追求到一种“动态平衡”。
“定制”，所强调的是产品的独特性。产品扩散自然地会导致公司持续不断地推出新品种，进而催生新的变化和生产过程的转换。这种情况违背了规模生产能够获得低成本的初衷，而规模生产的灵活性是受限的，强调的是其稳定性。这样的设置，就给产品开发者提出了一个特殊挑战。至关重要的是要为设计者提供产量，产品质量以及设计概念等各方面的反馈信息，以保持整个产品系列的完整性和连续性，因此，只有这样才能够充分利用现有的设计成果和制造投资。
并行工程（CE），作为解决这一系列问题的主要方法，其主要的特点是以产品设计为重点。CE，注重是对设计过程的审议，寻求的是对产品设整个生命周期中的关注，如美学，人体工程学，市场可承受力以及制造力。在并行工程实施过程中，设计过程，产业信息，制造业指标相互之间的联系一直是CAD / CAM技术发展的重大障碍。很多新技术已经发展和成熟起来用以为攻克这一系列难题架设一座桥梁，包括基于特征的设计和有限元分析等等。旨在完成继续保持经济发展规模这一挑战，文本介绍了另一方法，即设计制造仿真（DMS）。这个方法可以作为设计时的一种辅助工具，它由戈萨德首先提出。在他的方法中，各种零部件得以在计算机上完成设计，制造及仿真；因此，设计者能够最大限度的保证所设计的零部件真正都是自己想得到的。模拟根据设计（SBD）是一种类似并行工程（CE）的方法，成功推广这一方法的是在二十世纪九十年代早期时的DARPA （高级防御研究计划局）。SBD是指利用计算机模拟技术为虚拟样机设计提供设计系统。虚拟样机设计是通过模拟根据设计的设计系统和虚拟环境完成的。
另一方面，很多市场研究人员指出拥有亮丽外表的一种新产品更加能够吸引消费者的目光。这种拥有亮丽外表的新产品确实能够吸引消费者，并且通过了解用户使用产品后的反馈信息还能够给产品增值。因此，确定哪些因素能够增加消
费者购买本公司产品的几率，这对工程设计人员是至关重要的一个问题。由于考虑到这一点，高效快速的收集消费者的反馈信息将非常有助于整合专业市场营销人员与设计人员之间相互协调的优势作用。
至于产品的外观，消费者的反应主要取决于产品是否符合美学要求和人体工程学标准。
一种新产品是否适合现有设计趋势同样会使消费者产生不同的偏好。因此，如果设计的产品更迎合容易接受新产品的消费者可能会发挥重要的市场作用。虽然对于产品的完整性和典型性可能是消费者的最关心的两个方面，但是产品个性化的外表同样也是消费者所期待的另一个方面。因此，在设计之初，设计小组调查研究消费者对最终目标产品的外观的喜好情况就是十分重要的一项工作了。
传统上，市场分析技术通常采用向发放客户调查问卷的形式以获得消费者对设计产品的偏好情况。例如，联合分析这样方法被广泛地用来测试消费者对不同产品偏好情况，也用来帮忙相关人员建立市场模拟模型。拉亨斯-波特采取一种聚焦式的方法，用来为新产品提供一种有用的基于现实依据的设计参考。然而，虽然一些研究人员赞同客户的偏好情况，分配方法以及市场信息对产品设计的重要性，但是如何捕捉消费者对产品的口味，就目前的实际情况而言，他们仍未对这一现象引起足够的重视。换句话说，消费者对产品外观的偏好和设计制造者对反馈信息的处理这两个方面对产品的设计都是非常重要的。
在产品开发过程中，物理样机经常需要迭代评估，以提供反馈信息进而为产品做出设计修改，如设计多样性的选择，工程分析，制造规划和产品的可视化。甚至对运用传统工艺非常熟练的工程技术人员而言，为了制造物理样机所花费的时间，精力和费用都是巨大的。快速成型（RP）系统能够在很短的时间内完成高精度的模拟样机。设计一开始，这种系统就是质量非常高的3D CAD模型，在此基础上进行实体建模，然后以一种格式进行后期处理。例如，光固化，使得这种系统适合于物理样机。
2.2 虚拟样机的类型
虚拟样机主要有两种类型，即沉浸式虚拟样机和分析式虚拟样机。最近，由于在图形开发方面发生了快速的发展和进步，使得复杂的图形能够以准确快速的方式显现出来。这些陈述，当凑上新的发光二极管与人机界面，如数据库和耳机，可以帮助用户提供一些信息，即对象实际存在。虚拟触觉的影响对图形输出的准确性之间的关系是非常重要的，这种沉浸式虚拟样机模型，可以用作可视化和交互式的必不可少的数据库。这种虚拟形式更有利于完成有用的虚拟样机，在产品方面的发展，也正无时不刻暴露出一些弊端，如怎样向用户解释对这种虚拟样机，用户可以使用标准的计算机设备（鼠标，键盘，屏幕等）就可以做到设计仿真模拟。可以说，这种技术可以使人达到身临其境的效果。除了其身临其境的效果外，虚拟样机将可以省去繁琐的产品研发过程，使其变得非常方便快捷。不过，将这种技术应用到虚拟样机整机的有效地整合与分析，这在目前看来似乎仍
然是一个难题。