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西南交通大学本科毕业设计（外文翻译） 第10页THE DEVELOPMENT OF AN INTERNET-ENABLED SEMIAUTOMATED FIXTURE DESIGN SYSTEMA.Senthil kumar, S.H Bok, R.Kiran Kumar and A.Y.C NeeDept. of Mechanical and Production EngineeringNational University of SingaporeAbstractDesign of a fixture e is a complex and an intuitive process. An efficient fixture design system is essential to cut costs and to reduce lead-time. This paper addresses the development of a simple Internet-enabled semi-automated Fixture Design system (SFD), to demonstrate that true 3D fixture design can be carried out over the Internet. The whole system has been developed in Java and Javd3D to ensure that the benefits of Java technology are obtained for Internet viability considerations such as portability and good client-server computing performance. The system is currently implemented based on a simple 3-tier thin client-fat server architecture using Javas Remote Method Invocation (RMT).Design communications are currently carried out in the form of an open, self-extensible Xtensible Modeling Language (XML) scheme. The developed system coupled with a standard fixture element database so that the user will be able to carry out the task of designing the fixture assembly, while the bulk of the computation in terms of future design rules and constraints is carried out on a central server. The development of this system aims to provide users with easy access to basic fixture design functionality at a small fraction of the cost of employing a dedicated commercial modeling program operating as a backend. 1. INTRODUCTIONFixtures are work holding devices that are commonly used in manufacturing operations such as machining, inspection, assembly, etc. wee, 19951. The basic purpose of fixture elements is to repeatedly and consistently locate, support and clamp work-pieces for manufacturing operations to be performed. Fixturing solutions are provided in the form of modular fixture systems by vendors like IMAO, Kipp, Bluco Technik,Halder and Warton Unitool. These are made up of sets of ready-made and reusable standard components that can be assembled like Lego building blocks to handle a wide variety of shapes and sizes. The basic components of such systems include base plates, locators, stop elements and clamps. The greatest benefit that these systems offer is design flexibility. A complete set of modular fixture system is extremely versatile and can be configured in many ways to suit a whole rage of work-pieces and machining operations. However, this very feature of such a modular system also means that tool designers are constantly challenged to come up with feasible and sound fixture configurations. This is especially crucial with the current trend towards Flexible Manufacturing Systems (FMS) and with batch sizes becoming smaller to cater to increased customizations Dai, 19961. An expert fixture design system based on a CAD/CAM system would provide a way out. It would contribute towards cutting down of costs and lead-times, in accordance with the aims of automated manufacturing. With the advent of the Internet, many businesses have adopted the Internet as a communication platform or even port some of their core operations onto it. This has enabled them to perform almost instantaneous transactions with their partners worldwide. The manufacturing community should also adopt this approach in their operations, including fixture design. This is especially crucial with the push in the industry to implement distributed manufacturing and to offer rapid manufacturing capabilities Smith, 19961. An Internet- enabled system for fixture design would not only save costs and time, it would also help to promote new levels of collaboration between designers and their counterparts, as well as with clients, regardless of geographical constraints. The ultimate aim of the proposed system would be to allow users economical and easy access to fixture design functions, and be able to work on fixture designs or be able to present solutions to their clients even while they are on the move, utilizing any form of computing platforms.2. LITERATURE SURVEY2. 1 Standalone SystemsA number of semi-automated and automated fixture design systems have already been developed and implemented onto the CAD/CAM systems. Such systems provide fixture design functions such as a parametric fixture element database Yap, 1999 and built-in interference checking routines to ensure collision-free design solutions Dai 1997 and to provide for cutter path allowances Senthil kumar, 2000. These systems are all based on standalone machines or closed license based networks. One of the greatest drawbacks of these systems is the extremely high capital investments that would have to be incurred in order to set up the commercial modeling packages need to drive them. Another problem faced is the issue of having to constantly maintain and upgrade as newer versions of the fixture design systems and the CAD/CAM platform being developed and introduced. The proposed system would provide an alternative to this and offer fixture design functions at a small fraction of the costs need to implement these systems. It would also remove the need for users to constantly perform upgrades.2.2 Internet-Enabled SystemThe Internet has expanded rapidly over the last few years and will continue to do so in the foreseeable future. It has grown from just a means of posting and tracking articles and data to a rich medium of exchange that offers a multitude of services. As Internet infrastructure and net- working bandwidth continue to improve with advancement in technology, it makes sense to tap the potential of this rich resource in the field of manufacturing. Well-developed Internet-enabled manufacturing applications would bring about huge time and cost savings by harnessing the high speed communication and mass access features of the Internet. As with any Internet-based service, the new fixture design system will have a very wide end-user reach; it can be offered at a very low cost compared to systems implemented on license-based commercial modeling packages. It would not incur any set up costs on end users. They will be able to download an enabling client program that can access the fixture design functionalities hosted on server machines and be charged only when they make use of the program. Many potential end-users are likely to prefer such an option as opposed to having to dedicate large amount of resources in a costly dedicated system. This opens up a new segment of the manufacturing community to automated fixture design solutions.2.3 Java und Java3DFixture Net offers simple fixturing solutions accessible over the Internet using a Web browser Wagner, 19961. This system presents several limitations. Interaction with the fixture design service is not real-time and the time taken to return solutions is quite substantial. Being browser based, the user interface is also largely constrained by hypertext transfer language (HTML). Visualization of the work-piece and fixture elements is also confined to 2-dimensional layouts. Hence it is proposed to offer real-time 3-dimensional fixture design functions on the Internet. Built upon a prototype solid modeling interface, the system will present users with the options of loading a predefined work piece to utilize the fixturing functions or to model the work-piece using the modeling functions of the solid modeling interface itself. This would be a more true-to-life system design. Another important feature of the new system would be its multi client support. Two or more users would be able to simultaneously work on the same work-piece from different remote locations.Basic interactive fixture design (IFD) functions across the Internet have been developed. The user will have to make most of the decision as to the choice and positioning of the fixture elements. The main objective of this initial version is to demonstrate the feasibility of true 3D-fixture design remotely over the Internet implementing client-server architecture. Further improvements are made and a simple semi-automated fixture (SED) has been developed. Improvements are being made to develop a fully automated fixture design (AFD) functions in order to achieve a truly comprehensive system.3. SYSTEM ARCHRECTURE?The whole system has been developed using Java and Java3D. The decision to adopt Java as the programming language of choice was based on its cross-platform portability. This is important to provide good overall client-server performance of the system and to ensure its Internet viability. This fixture design system aims to reach out to a whole range of potential end users who might be operating on a variety of operating platforms such as Windows98, Windows NT, UNIX and Linux. By implementing the client enabling-program purely using Java, Java3D and various Java APIs, any user will be able to make use of the fixture design functions as long as he/she has access to a machine with a Java Virtual Machine (JVM) running. The fixture design system has been built upon a design-modeling interface that offers all the basic capabilities of a constructive solid geometry (CSG) solid modeling system. These include all the primitive solid functions (block, sphere, cylinder and prism), Boolean operations (union, subtraction and intersection) and transformation operations (translation and rotation). A simple structural representation of the developed system is shown in Figure 1. It illustrates the 3-tier architecture of the system. The first tier comprises of the client side program which, as mentioned, is written entirely in Java. It is made up of a graphical user interface (GUI) that includes a work area, which displays the work parts and the fixture elements as 3D images.The solid modeling and fixture design functionalities are implemented using Java routines that also call on solid modeling kernel. These routines and the modeling kernel reside on the server end of the set up and they make up the second and third tiers of the system. Using Javas Remote Method Invocation (RMD facilitates the interface between client-side and server-side routines. The actual transfer of data for design communications is carried out in the form of an Extensible Mark-up Language (XML) schema.4 CONCLUSIONSThe aim of the developed system is to demonstrate the feasibility of a true 3D-fixture design solution that is enabled over the Internet. Such a system would not only reduce the costs and lead times in manufacturing operations, but also bring us a step closer to the realization of true global distributed manufacturing.Written in Java and implemented on thin-client-thick- server architecture, the system also aims to be fully portable across all platforms and be easy to maintain and upgrade. As an initial effort, the system at present only provide simple, user dictated interactive fixture design (IFD) and semi-automated fixture design (SFD) capabilities. Future developments are planned to implement automated fixture design (AFD) functions. Eventually the functionalities of the system will be extended beyond the scopes of fixture design to make up a fully self-sufficient Internet-enabled distributed design and manufacturing package.5 REFERENCESC. S. Smith and P. K. Wright, (1996). CyberCut: A World Wide Web Based Design-to-Fabrication Tool, Joumul of Munufucturing System, 15,432-442K.A. Yap, (1999). Development of a Semi-automated Modular Fixture Design System。B. Eng. Dissertation, National University of Singapore.J. R. Dai, (1997). Computer-Aided Modular Fixture Design and Assembly,M. Eng. Dissertation, National University of SingaporeA.Senthi1 kumar, J.Y.H Fuh and T.S.Kow (2000). An automated design and assembly of interference free modular fixture set-up, accepted for publication in Computer Aided Design.R. Wagner, et.al. (1996). Fixture Net: Interactive Computer Aided Design via the WWW, International Journal for Human- Computer Studies, 146- 15 3 互联网半自动夹具设计系统的发展A.圣西尔.库马尔,S.H波克,R.科曼.库马尔和A.Y.A.里新加坡国立大学机械学院与生产工程学院摘要夹具设计是一个复杂和一个直观的过程。一种高效夹具设计系统对降低成本和减少所需的时间来说是必要的。这篇文章介绍了一个简单的互联网半自动化夹具设计系统的发展(SFD)，为的是证明实体的三维夹具设计是可以在因特网上进行。整个系统通过JAVA和JAVA3D设计以确保在因特网上的可实行性的,该系统必须具有网上生存的条件,例如可移植性和良好的客户服务器计算性能。 这个系统立足于3层服务器结构上运用JAVA的远程调用方法来实施的。 设计通信是以一种开放的，自我扩展成模块的语言来实施的。 一个先进的设计系统再加上一个标准夹具元件库,使用户能完成夹具装配的设计任务， 虽然在今后的设计中大部分的计算都会被限制在一个服务器中。开发这一系统的目的是为用户提供方便的夹具设计功能,用一个小的成本聘请一个专门商业建模程序作为你设计的后盾。 1.简介夹具其实就是一种夹持工件的装置,常用于加工操作,例如加工,检验,装配等。 夹具元件的基本宗旨是重复并持续的定位,支持和加紧工件让加工可以顺利的进行. 夹具的解决方案都是由夹具的供应商如IMAO, Kipp, Bluco Technik,Halder 和 Warton Unitool，以如何调节夹具的方式提出的. 这些方案都是用现在常用的标准组件来组合而成的,就像用Lego积木来堆积各种各样的形状和尺寸一样. 这些系统的基本组成部分包括工作台、定位元件、挡板和夹紧元件. 这样设计的系统最大好处是可提供设计的灵活性. 一套完整的夹具系统应该是非常灵活,可灵活地配置在各种大型的工件夹具或机床. 不过,模块系统的这个特征意味着设计师们将不断被怀疑能否实现可行性和完善夹具配置. 这一点尤为重要,因为目前夹具的趋势是柔性制造系统(FMS)和尺寸越来越小, 以实现要求的精度。基于CAD/CAM系统的专家级夹具设计系统为此将提供一条好的出路， 它将按制造自动化的宗旨有助于降低成本和周转时间。随着因特网应用越来越广泛，许多企业都把因特网作为一种沟通的平台,甚至把他们重要的业务都放在上面. 这使得他们与世界各地的合作伙伴的交易瞬间完成。机械行业包括夹具设计也应该采取这种方式。这对于推动工业界实现分散制造和提供快速制造能力是特别重要的 。 因特网使夹具设计系统不仅能节省成本和时间. 它也将有助于促进设计师与他们同行之间新层次的合作, 以及不分地域限制地与客户的协作,最终目标建立的系统将会保证用户经济效益并轻松掌握夹具设计功能, 并能利用任何形式的计算机平台进行夹具设计,或能解决客户提出的问题. 2 综合叙述2.1独立系统很多半自动及自动夹具设计系统已经开发成功并用在CAD/CAM系统上. 这些系统提供夹具设计功能,如参数化夹具元件库和内在干涉的例行检查,以确保无碰撞的设计解决方案，并为他们提供走刀余量. 这些系统都是基于独立机器或关闭的网络. 这中系统的一个最大弊端是需要非常高的投资,这将有可能导致 人们为了建立商业建模软件包而不要他们. 另一个面临的问题是要一直维护和升级为新版本的夹具设计系统和CAD/CAM平台将不断的开发和引进.正在建设的系统为此提供另一种选择,只要花很少的钱就能实现夹具设计系统的这些功能. 它也将需要用户不断地进行升级.2.2网络系统互联网在最近几年迅速的扩张,并在可预见的将来也将是这样. 它已从一种投寄邮件及跟踪文章和数据传输手段发展到提供多种服务的交流媒介. 随着科技进步，互联网基础设施和网络带宽的不断改善 ,我们很应该挖掘制造业在这方面潜在的丰富资源. 利用高速通信和集体 Access特色的互联网，发达的互联网使制造业的应用会带来巨大的时间和费用节省。 因为有了互联网的服务,新的夹具设计系统将有一个非常广泛的终端用户出现。它可以提供一个相比于独立系统有着非常低成本的商业模型软件包. 它不会对最终用户带来配置成本的问题.将可以下载一个有效的能够进入夹具设计功能服务器的客户程序，只有使用它的时候才收费. 许多潜在的终端用户更喜欢这样的选择,他们不喜欢花大量资源来配置一套昂贵的专用系统. 对自动夹具设计方案来说，它开辟了制造行业一个新的领域。2.3 java和java3d夹具设计网在互联网上通过网络浏览器提供简单夹具解决方案. 这一系统存在一些局限，互