CA6140车床尾座体工艺工装设计【说明书+CAD】
CA6140车床尾座体工艺工装设计【说明书+CAD】,说明书+CAD,CA6140车床尾座体工艺工装设计【说明书+CAD】,ca6140,车床,尾座体,工艺,工装,设计,说明书,仿单,cad
江阴职业技术学院毕业设计说明书江阴职业技术学院毕业设计说明书课 题:CA6140车床尾座体工艺工装设计子课题: 同课题学生姓名: 专 业 机电一体化 学生姓名 徐长喜 班 组 04机电(一)班学 号 指导教师 完成日期 20070401 目 录摘要3ABSTRACT4第一章 引言51.1机械制造业的发展趋势 6 1.2 健康绿色的制造业8 1.3课题来源12第二章 设计介绍 132.1材料的选用 132.2 中心架总成132.3 部件组织结构的注意点14致 辞15参考文献16 CA6140车床尾座体工艺工装设计摘要本文针对目前比较常见的机床CA6140车床尾座体工艺工装设计,经过对成品的观察与分析,以及实际操作时的经验、测量,特设计出该类中心架的生产图纸。因为本人水平有限,文章中难免存在着不足与缺陷,望广大读者批评指正。关键词:中心架 CA6140车床尾座体工艺工装设计 C6140 machine-center designAbstract view of the current more common C6163 Machine Tool Center frame for design, right through to the finished product observation and analysis, and the actual operational experience, measurement, Special design of such centers-production drawings. Because I was limited, and it is inevitable that the article had weaknesses and deficiencies and hopes readers criticized corrected. Keywords : center C6163 machine tool design 第一章引言随着现代制造业的发展,越来越多的设备被运用到制造业中,而制造业也需要越来越多的设备来满足发展。企业需要发展,就需要投入相应的设备来满足企业的需要,但是面对众多的新设备,这些设备的配件夜成为了我们越来越高的需求。本文我将结合CA6140车床尾座体工艺工装设计,对原有的中心架进行修改,以设计出一台新型的满足一般企业需要的中心架。由于条件不足,且本人经验和水平都还很有限,设计中一定存在许多不足之处,望各位老师给予指正。- 17 -1.1 机械制造业的发展趋势随着当今社会的发展机械制造行业受到了越来越多人的关注,而目前机械制造业的发展趋势有以下几个特点柔性化、灵捷化、智能化和信息化一、柔性化使工艺装备与工艺路线能适应于生产各种产品的需要。二、灵捷化使生产力推向市场准备时间为最短,使工厂机械灵活转向。三、智能化柔性自动化的重要组成部分,它是柔性自动化的新发展和延伸。四、信息化机械制造业将不再由物质和能量借助于信息的力量生产出的价值,而是由信息借助于物质和能量的力量生产出的价值,因此信息产业和智力产业将成为社会的主导产业,机械制造业也将是由信息主导的,并采用先进生产模式、先进制造系统、先进制造技术和先进组织合理方式的全新的机械制造业。21世纪初机械制造业的重要特征表现在它的全球化、网络化、虚拟化以及环保协调的绿色制造等,人类不仅要摆脱繁重的体力劳动,而且要从烦琐的计算分析等脑力劳动中解放出来,以便有更多的精力从事高层次的创造性劳动。智能化促进柔性化,它使生产系统具有更完善的判断与适应能力。近年来产品更迭不断加快,各种各样的需求不断增加。一些发达工业国家,例如美国、西德、瑞士等国统计表明,1995-1998年机械零件的种类增加了50%;80%的工作人员不直接与材料打交道,而与信息打交道;85%的活动不直接增加产品的附加值,产品、工艺过程、组织管理日益复杂化;设计、工艺准备等均占去为完成用户订货总时间的65%以上。另一方面,在激烈的市场竞争中,供货期与质量往往起着比价格更为重要的作用,灵捷化就成为摆在机械制造业面前的头等重大课题。机械制造行业是创造人类财富的支柱产业,但同时又大量消耗掉人类社会的有限资源,并且是造成当前环境污染问题的主要根源之一,为此,机械行业实施可持发展战略已势在必行。绿色制造正是基于这一点而产生和发展起来的,是机械行业的发展趋势,或者说绿色制造是21世纪制造业的可持续发展模式。传统制造业已不适应可持续发展的要求 传统制造业一般是纯粹从经济效益的角度去实施制造过程的,在设计产品时着力考虑产品的功能与品质,制造产品时片面追求高效率与低成本。不断涌现的新颖高效的先进制造技术推动了制造业的快速发展,产品更新换代周期不断缩短,加速了材料的消耗和工艺装备的淘汰;同时也产生了更多的废弃物,从而使人类赖以生存的环境不堪重负,严重制约了社会经济及人类文明的可持续发展。目前在环境保护方面,制造业存在以下问题:1.废旧或闲置设备回收和再利用率低 近年来,由于数控机床、加工中心及FMSCIMS的应用,大多数传统机床在工厂逐步被摒弃。如何改造这些旧设备成了摆在我们面前的一大课题。2.能源和原材料的浪费现象十分严重 目前,我国制造业工艺水平不高,多数企业缺乏环保意识。落后的制造工艺使得能源与原材料的利用率不高。且浪费也十分严重。3. 产品的回收利用率极低 长期以来,传统的生产模式是按照“生产一流通一消费一废弃”的开式循环。制造业的生产基本上不考虑废弃产品的回收利用,特别是机械制造业的回收利用率更低。4.制造过程中产生的废弃物得不到无公害处理 许多企业在产品制造过程中,注重的是如何以最低的成本高效地生产出产品,而很少关心加工过程中使用的工具及原材料等对环境的污染。高能耗、重污染的工艺仍然在生产中得到广泛的应用,而先进的环保型工艺由于成本较高而被搁置,企业不愿在治理废弃物方面有所花费。这样一来,在企业获得较高利润的同时,人类生存的环境却遭到了前所未有的破坏。随着这总形式的严峻发展,一个新的课题又摆在了我们的面前:如何在目前的基础上改造我们的机械制造业,使我们的制造业逐渐走向绿色、健康、环保的大道。1.2 绿色健康的制造业 工业革命以来,人类社会经过100多年的快速发展,目前已经面临社会发展与环境和资源之间的深刻矛盾。在人类对自己长期以来采用较为粗放的、大规模工业发展模式及由此而引起的资源枯竭、环境恶化等问题的反思之后,如何选择一条适合该国国情的可持续发展道路,实现人与自然的和谐相处,成为世界大多数国家的共识。这种共识的代表就是1972年在瑞典斯德哥尔摩召开的“联合国人类环境会议”通过的人类环境行动计划,1992年联合国在巴西里约热内卢召开的“世界环境与发展大会”通过的关于环境与发展的里约热内卢宣言、21世纪议程,以及2002年联合国在南非约翰内斯堡召开的“可持续发展世界首脑会议”通过的关于可持续发展的约翰内斯堡宣言与可持续发展世界首脑会议实施计划,其核心是提出了应建立社会、经济、资源和环境相协调的可持续发展战略。 作为人类社会可持续发展的重要标志,是使子孙后代拥有与当代人相同,甚至比当代人还多的人均财富和生存发展空间。这就要求当代人要有对历史和子孙后代负责的精神,切实地改变现在传统的发展思维模式以及由这种思维模式而产生的生产、生活和经济发展方式,特别是在这么一个经济快速增长、人口众多、人均资源不到世界平均水平1/2的发展中国家更是如此。应该看到,由于中国经济基础薄弱,技术相对落后,发展大部分是通过以自然资源和劳动力为主要的投入手段所推动的,是一种粗放型的经济增长方式。这种发展的结果,是现在面临越来越严重的资源短缺和生态环境恶化问题。 经济发展必须有利于资源的良性利用,有利于生态系统的良性循环,有利于改善和提高人民的生活水平;而不能以浪费资源、破坏生态环境和降低人民生活质量为代价。党中央提出了“要树立以人为本,实现全面、均衡和可持续的科学发展观”,这体现了中国政府在国家经济发展基本模式上观念的进步。作为可持续发展战略的重要组成部分,以绿色设计和绿色制造为主要特征的绿色浪潮正在席卷全球。通过绿色设计和绿色制造,人们希望实现对资源的循环利用、降低能源消耗和最大程度地减小产品制造和使用对环境的影响,实现可持续发展的目标。 下面,从机械产品设计理念的角度,讨论绿色设计理念对机械设计的影响。 机械产品绿色设计的概念 有关机械产品绿色设计概念方面的研究,国内近年来进行得比较多。机械产品绿色设计的概念可归纳为:机械产品绿色设计是一种基于产品整个生命周期,并以产品的环境资源属性为核心的现代设计理念和方法,在设计中,除考虑产品的功能、性能、寿命、成本等技术和经济属性外,还要重点考虑产品在生产、使用、废弃和回收的过程中,对环境和资源的影响。 其基本的内涵有: (1) 在产品设计的全过程中,产品的基本技术性能属性与环境资源属性、经济属性并重,且环境资源属性优先。 (2) 在设计阶段应充分考虑产品在使用废弃后的可拆性和回收利用性。 (3) 提出了产品设计者和生产企业在环境保护、节约资源方面应承担的社会责任。即对大宗工业产品,企业不但要生产产品,同时,还应在可能的范围内,承担产品回收和再利用的义务。 (4) 它是对传统设计方法、设计理念的发展和创新,体现了人类对机械产品设计学科认识的深化。 传统的机械产品设计侧重的是产品的性能、质量、成本等产品的基本技术与经济属性,对产品的考虑最多到产品使用报废为止。按传统的机械产品设计理念,在产品使用报废后,就成了一堆废铁和垃圾,与制造企业也没有任何关系,报废产品金属零件的回收利用主要采用回炉冶炼方式,很少直接利用因而是一种“从摇篮到坟墓”的过程。 所以,绿色设计与传统设计的根本区别在于:绿色设计要考虑产品的整个生命周期,从产品的构思开始,在产品的结构设计、零部件的选材、制造、使用、报废和回收利用过程中对环境、资源的影响,希望以最小的代价实现产品“从摇篮到再现”的循环。 绿色设计理念对现代机械产品设计的影响 想法决定生活,理念决定设计。理念或观念的进步对社会发展有巨大的推动作用,理念虽然不是具体的方法,但理念可以为具体方法的研究指引方向,而具体的设计方法,是建立在一定的设计理念之上的,理念是具体方法的基础。纵观人类机械产品设计理念和产品设计技术的进步历程,不难看出,设计理念的进步给产品设计带来的巨大影响。从机械设计学科的角度,近代设计方法学的发展主要体现为: “功能思想”的提出; “人机学”思想的形成; “工业设计”学科的发展和成熟。 在这三项近代机械设计学科的核心技术中,对后来机械产品设计的影响,都首先体现在由于它们出现而带来的设计理念的进步,其次才是具体的方法,所有先进的具体设计方法如:优化设计、可靠性设计、CAD等等,都是为实现设计理念服务的。 例如:以美国人麦尔斯“顾客购买的不是产品本身,而是产品所具有的功能”为标志的“功能思想”的提出,并逐步为人们广泛的理解和接受后,使设计者认识到:可以采取不同的原理、结构来实现同样的功能,它所带来的是人们在设计思想上的一次革命,大大地拓展了设计人员的视野,在此之前,人们在设计时,更多的是用数学、力学的方法来研究机械的设计,用更合理的结构设计去完善已能完成某种功能的机器,忽视了作为产品本质的“功能”的研究。正是在功能思想的指导下,涌现出了大量采用新的功能原理的产品,如电子手表、激光打印机、喷墨打印机以及现在的数码相机等。 绿色设计作为一种新的设计方法,出现的时间并不长,还远没有达到完善的程度,很多具体的方法还有待研究,但绿色设计作为一种新的设计理念,它的出现,使人们看到了过去设计思想方法的不足,意识到了在过去长期的设计活动中,所忽视的产品设计与环境资源之间的关系和产品设计对环境、资源的影响。绿色设计理念的提出,是机械设计学科发展历史上一个重要的里程碑,是机械设计理念的一次革命和飞跃,它对现代机械设计学科所带来的革命性影响主要表现为: (1) 第一次从人类整体利益的高度,强调了设计者、生产企业在人类社会可持续发展和环境资源保护方面应该承担的社会责任。这种责任一方面可以通过国家法律的形式强制企业承担,如汽车尾气的排放法规、锅炉的尾气排放法规、工业废水的排放法规等,而更重要的是作为设计者和生产企业,必须主动意识到自己应承担的社会责任,在企业的产品开发、生产和企业发展过程中,能进行自我约束,不能仅仅为了实现自己企业商业利益的最大化,而置社会利益于不顾。当今所面临的环境污染和资源短缺等问题,并不是由于个别企业或某一行业的行为造成的,而是整个社会在一段时间内共同行为的累计结果。所以,绿色设计理念反映了人们对现代生产方式和生活方式所引起的生态和环境破坏的反思,从道德层面上提高了对设计师和企业素质的要求,代表了一种新的设计文化,反映了人类道德认知水平的提高,这种提高和认识的深化,必将从更高的层次上,推动社会文明的进步和实现所追求的人类社会可持续发展的理想。绿色设计所代表的是“以人为本,实现人与自然和谐相处”的现代设计文化。所以,如果说“功能思想”的提出是在技术层面上推动了设计学科的进步;而“绿色设计理念”的提出是在人的思想道德和设计文化的层面上推动了设计学科的进步,它体现了:“地球环境与资源保护是大家的共同责任”的崇高思想。 (2) 对机械产品来讲,设计是源头。今天所面临的主要由工业设备、工业产品制造与使用所造成的环境污染、资源浪费等问题,除受当时时代的科学技术发展水平的限制,对可能引起的问题预见、认识不够有关外,还在很大程度上与一些传统落后的产品设计理念有关。例如:在过去的设计理念中,几乎不考虑环境问题,也不考虑产品的回收利用问题,并将烟囱林立、浓烟滚滚、污水横流、机器轰鸣等看成是工业化的标志就是最典型的代表。对所制造和销售的产品与企业和设计人员的关系,现在很多设计人员仍认为“产品过了保修期就与自己和企业没有关系了”。所以,必须改变产品设计的传统观念,要树立“今天的产品,就是明天的废品”的产品设计理念,从产品的性能、材料选择、制造、使用、合理的产品寿命、报废回收的整个过程来看待现在正进行的产品设计,尤其是考虑产品报废后的回收性,进行综合平衡和决策,树立全新的绿色产品设计理念。 (3) 对报废产品的重新认识。当今社会,科学技术发展很快,新产品层出不穷,产品的有效寿命周期明显缩短,很多产品不是因为不能使用,而是由于性能落后或仅仅由于外观老旧而报废。虽然可以花钱买新的,但被废弃的不仅是报废的产品,而且还有废弃产品中所包含的资源。所以,绿色设计强调对“物理报废”和“性能报废”产品的回收和再利用。为此,要在产品设计的各个环节上综合考虑对产品整个寿命周期的影响,对产品技术的发展有科学的预测,在现有产品、储备产品和研发产品之间有合理的技术继承和联系,充分考虑由于产品款式、技术升级等因素引起的产品报废,使产品具有合理的使用寿命,而不一味地追求产品的经久耐用。同时,在设计中,广泛运用现代的设计技术,如采用系列化、模块化和标准化设计技术,在产品设计中考虑产品零部件的技术和结构的继承性8,为产品在报废后的再制造奠定技术基础。运用面向拆卸的设计技术,注意考虑产品的装拆结构设计,方便装拆。同时,还应考虑对一些产量大、使用时间长的产品,在技术进步后,如何对已销售的产品进行合理的、较为经济的改装,以提高产品使用性能的设计方法,例如像家用空调、电冰箱等产品就是属于这种情况。由于技术进步,现在产品的耗电量较前几年已经明显降低,如前几年普通电冰箱24h耗电量为1kWh左右,但现在可以达到0.4kWh左右,与现在新的节能型电冰箱相比,大量还在使用的老电冰箱就像电老虎一样每天都在大量地消耗宝贵的电力。但由于这些老冰箱不能以较为方便的方式和用户能接受的价格实现节能方面的改装,依然会在若干年内继续使用这些弃之可惜的冰箱,并为它们多使用的电付钱,造成社会资源的巨大浪费。从政府的角度讲,如何在政策上大力鼓励和扶持对报废产品的再制造是值得研究的。1.3 课题来源 面对目前提倡的绿色制造特有这样的想法:利用有限的资源以及现有的技术设计出一种CA6140车床尾座体,使其制造成本降低、实用度提高、且容易制造。 下面一章我将对我的设计作出具体的阐述。第二章 设计介绍21材料的选用 根据中心架的特点以及对材料的要求,所以我选用的材料为:35、45Q235A、HT150以及ZQSnCu6-6-3。22 中心架总成图一如图一所示本中心架最大夹件直径为350,其主要配件为:圆销、特厚螺母、活结螺栓、垫圈、销轴、螺母、法兰、螺钉、锥销、丝杆、轴承、套筒、定位销、轴、挡圈、锥销锁紧挡圈。其中部分利用现有的标准配件,如:GB 6885、GB 11786、GB 617086等,具体的配件位置件装配总图。2.3 部件组织的注意点焊接件上体,筋板焊前周边加工,点焊后连续焊接,焊后应无焊接缺陷如图二图二 所有需要热处理的工件,热处理必须达到要求,严格按照热处理工艺进行处理。谢 辞这次设计的完成,无疑地需要很多人的帮助。首先要感谢的是指导老师,他不但帮助我解决有关调研方面遇到的棘手问题,还帮我解决了许多以前课程学习时就没有搞清的问题。当然我还要感谢许多给过我帮助的同学们,没有他们的热心协助,我是无法完成这次设计任务的。最后我也要向相关老师致谢,没有他们的谆谆教导,我就没有一定的理论基础,更不用说能够搞好这次设计。再次感谢诸位!参 考 文 献1.吕惠瑛等编机械设计基础上海:交通大学出版社,20012.王广生等编热处理手册第三版北京:机械工艺出版社,20013.曾正明主编机械工程材料手册第六版北京:机械工艺出版社,20034.王文斌等编机械设计手册新版北京:机械工业出版社,2004 5.陈宏钧主编实用机械加工工艺手册第二版北京:机械工业出版社,2003Proceedings ofthe2006 IEEE/RSJ International Conference on Intelligent Robots and Systems October9- 15, 2006, Beijing, China ANovelModularFixtureDesignandAssemblySystem BasedonVR PengGaoliang, LiuWenjian SchoolofMechatronicsEngineering HarbinInstituteofTechnology Harbin, 150001, China pgl7782a Abstract - Modular fixtures are one oftheimportant aspects ofmanufacturing. This paper presents a desktop VR system for modular fixture design. The virtual environmentis designed and the design procedure is proposed. It assists the designer to make the feasible design decisions effectively and efficiently. A hierarchical data model is proposed to represent the modular fixture assembly. Based on this structure, the user can manipulate the virtual models precisely in VE during the design and assembly processes. Moreover, the machining simulation for manufacturing interaction checking is discussed and implemented. Finally, the case study has demonstrated the functionality of the proposed system. Compared with the immersive VR system, the proposed system has offered an affordable andportable solutionformodularfixtures design. Index Terms - Modularfixture, desktop VR, assembly design, machiningsimlulation. I. INTRODUCTION Modular fixtures are one of the important aspects of manufacturing. Proper fixture design is crucial to product quality in terms of precision, accuracy, and finish of the machined part. Modular fixture is a system of interchange- eable and highly standardized components designed to securely and accurately position, hold, and support the workpiece throughout the machining process 1. Tradition- ally, fixture designers rely on experience or use trial-and- error methods to determine an appropriate fixturing scheme. With the advent of computer technology, computer aided design has been prevalent in the area of modular fixture design. In general, the associated fixture design activities, namely setup planning, fixture element design, and fixture layout design are often dealt with at the downstream end of the machine tool development life-cycle. These practices do not lend themselves well to the bridging of design and manufacturing activities. Forexample, very few systems have incorporated the functionality of detecting machining interference. This leads to a gap between the fixture design andmanufacturing operationswheretheaspectofcutterpaths is not considered during the design stage 2. As a result, re- designcannotbeavoidedwhenthecutterisfoundtointerfere with the fixture components in the manufactu- ring set-up. Therefore, in orderto bring machining fixture design into the arenaofflexiblemanufacturing, amoresystematicandnatural designenvironmentisrequired. As a synthetic, 3D, interactive environment typically generated by a computer, VR has been recognized as a very powerful human-computer interface for decades 4. VR holds great potential in manufacturing applications to solve problems before being employed in practical manufacturing thereby preventing costly mistakes. The advances in VR technology in the last decade have provided the impetus for applying VR to different engineering applications such as product design 5, assembly 6, machining simulation 7, andtraining 8. The goal ofthis paper is to develop a VR- basedmodular fixtures design system (VMJFDS). This is the firststepto develop anintegratedandimmersiveenvironment for modular fixture design. This application has the advantages of making the fixture design in a natural and instructive manner, providing better match to the working conditions, reducing lead-time, and generally providing a significantenhancementoffixtureproductivityandeconomy. II. OVERVIEWOFTHEPROPOSEDSYSTEM The system architecture of the proposed desktop VR systemismodularisedbasedonthefunctionalrequirements of thesystem,whichisshowninFig.1. Atthesystemlevel,three modules of proposed system, namely, Graphic interface (GUI), Virtual environment (VE) and Database modules are designed. For each ofthe modules, a set ofobjects has been identified to realize its functional requirements. The detailed objectdesignandimplementation are omittedfromthispaper. Instead, the briefdescription ofthese three modules is given below. 1) Graphic Interface (GUI): The GUI is basically a friendly graphic interface that is used to integrate the virtual environmentandmodularfixturedesignactions. 2) Virtual environment (VE): TheVEprovidestheusers with a 3D display for navigating and manipulating the models of modular fixture system and its components in the virtual environment. As shown in Fig. 1, the virtual environment module comprises two parts, namely assembly design environment andmachiningsimulationenvironment. Theuser selects appropriate elements andputs downthese elements on the desk in the assembly design area. Then he assembles the selected elements one by one to build up the final fixture systemwiththeguidanceofthesystem. 1-4244-0259-X/06/$20.00 C)2006IEEE 2650 Authorized licensed use limited to: Nanchang University. Downloaded on December 20, 2009 at 22:44 from IEEE Xplore. Restrictions apply. Fig.1.OverviewofthedesktopVRbasedmodularfixturedesignsystem. 3) Database: The database deposit all of the models of environment and modular fixture elements, as well as the domain knowledge and useful cases. There are 5 databases shown in Fig.1. Among them, knowledge & rule base governing all fixture planning principles forms the brains of thesystem. III. PROCEDUREOFMODULARFIXTUREDESIGN In this section, an instructive modular fixture design procedure within VE is presented. Besides the 3D depth that the users feel and the real-world like operation process, this procedure features intelligence and introduction. During the design process, some useful cases and suggestion will be presented to the user for reference based on intelligent inference method such as Case based reasoning (CBR) and Rule based reasoning (RBR). Further more, relative knowledge andrules arepresented ashelppages thattheuser caneasilybrowsedduringthedesignprocess. Overview of modular fixture design process is summarized in Fig. 2. After the VE environment is initialed andthe workpiece is loaded, the first step is fixtureplanning. Inthis step, theuserfirstdecides thefixturing scheme, thatis specifies the fixturing faces of the workpiece interactively. Forhelptheusersdecision-making, someusefulcasesaswell as their fixturing scheme will be presented via the automatic CBR retrieval method. Once the fixturing faces are selected, theusermaybepromptto specifythefixturingpoints. Inthis task, somesuggestions andrulesaregiven. After the fixturing planning, the next step is fixture FUs design stage. In this stage, the user may be to select suitable fixture elements andassembletheseindividualparts into FUs. According to the spatial information ofthe fixturingpoints in relation to the fixture base and the workpiece, some typical FUs and suggestions may be presented automatically. These willbehelpfulfortheuser. AftertheplanningandFUs design stage, the next stage is interactively assembling the designed fixtureFUstoconnecttheworkpiecetothebaseplate. When the fixture configuration is completed, the result will be checked and evaluated within the machining environment. The tasks executed in this environment including assembly planning, machining simulation, and fixture evaluation. Assemblyplanning isusedto gain optimal assembly sequence and assembly path of each component. Machining simulation is responsible for manufacturing interaction detection. Fixture evaluation will check and evaluate the design result. In conclusion, the whole design process isinanaturemannerforthebenefitofVE. Moreover, the presented information of suggestion and knowledge can advise the user on how to make decisions ofthe best design selection. IV. ASSEMBLYMODELINGOFMODULARFIXTURE A. Modularfixturestructureanalysis A functionalunit(FU) is acombination offixture elements to provide connectionbetweenthebaseplate and aworkpiece 11. Generally, modularfixture structuremaybe dividedinto three functional units according to its basic structure characteristics, namely locating unit, clamping unit, and supporting unit. The number offixture elements in aFU may consist ofone or more elements, in which only one element serves as a locator, support or clamp. The major task ofthe modularfixture assembly is to selectthe supporting, locating, clamping and accessory elements to generate the fixture FUs toconnecttheworkpiecetothebaseplate. By analyzing the practical application ofmodular fixtures, it is found that the assembly ofmodular fixtures begins by selecting the suitable fixture elements to construct FUs, then subsequentlymountingtheseFUs onthebaseplate. Therefore, the FUs can be regarded as subassemblies ofmodular fixture system.Further,thestructureofmodularfixturesystemcanbe representedasahierarchalstructureasshowninFig.3. 2651 Authorized licensed use limited to: Nanchang University. Downloaded on December 20, 2009 at 22:44 from IEEE Xplore. Restrictions apply. UsefTa6 *T- siikg&Sugge lr,l Fixtui e Elemenets rUetrieval i0 Tools rKetrieval 4 Fig.2Modularfixturedesignprocedureinproposedsystem B. Hierarchically structured data modelfor modularfixture representation in VE It is common that the corresponding virtual environment may contain millions ofgeometric polygon primitives. Over thepastyears, anumberofmodel sub-division schemes, such asBSP-tree 10 andOctrees,havebeenproposedto organize largepolygonalmodels.However, formodular Ba 1I_ 1 Hsreplalte Bansepla1nte Elements *Locatng ElementsL,cating Units AccessoryEllements ClamnpingElemnents !ClampingUnits SupportingElemntsSupporting Ufnits Accessory Elements Fig. 3Hierarchical structureofmodularfixture system design applications, the scene is also dynamically changing, due to interactions. For example, in design process, the part object may change its spatial position, orientation and assembly relations. This indicates that a static representation, such as BSP-tree, is not sufficient. Further more, the above models can only represent the topology structure of fixture system in the component level. However, to the assembly relationship among fixture components, which refers to the mating relationship between assembly features that is not concerned. In this section, we present a hierarchically structuredandconstraint-baseddatamodelformodularfixture system representation, real-time visualization and precise 3D manipulationinVE. As shown in Fig.4, the high-level component based model is used for interactive operations involving assemblies or disassembles. It provides both topological structure and link relationsbetweencomponents. Theinformationrepresent- ed in the high-level model can be divided into two types, i.e. component objects and assembly relationships. Component objects can be a subassembly or a part. A subassembly consists of individual parts and assembly relationships betweentheparts. Component Level (Pt Part S Subassembly Assembly relationship Feature Level Ft3 Feature Feature mating relationship t- -t Polygon Level FZ-ll. Polygon Fig.4ThehierarchicalstructuredatamodelinVE Themiddle-levelfeaturebasedmodelisbuiltuponfeatures and feature constraints. In general, the assembly relationship often treated as the mating relationships between assembly features. Thus the featurebasedmodel isusedto describethe assembly relationship andprovides necessary information for spatial relationship calculating during assembly operation. In this model, only the feature relationships between two different components are considered. The relationship between features ofone element will be discussed in feature basedmodularfixtureelementmodelingbelow. The low-level polygon based model corresponds to the above two level models for real-time visualization and interaction. It describes the entire surface as an inter- connected triangular surface mesh. More about how the polygons organized of a single element will be discussed is thenextsection. C. Modularfixtureelementsmodeling As we know, in VE, the part is only represented as a number ofpolygon primitives. This result in the topological 2652 Authorized licensed use limited to: Nanchang University. Downloaded on December 20, 2009 at 22:44 from IEEE Xplore. Restrictions apply. relations- hips and parametric information are lost during the translation process of models from CAD systems to VR systems. However, this important information is necessary in design and assembly process. In order to fulfill the requirements, we present a modeling scheme for fixture elementsrepresentationinthissection. The modular fixture elements are pre-manufactured parts withstandarddimensions. Afterthefixturingschemedesigned, the left job is to select suitable standard elements and assemblethese elements to formafixture systeminafeasible andeffectivemanner. Therefore, intheproposed system, only the assembly features of the fixture elements need to be considered. Inthispaperanassemblyfeature isdefinedas apropertyof afixture element, whichprovidesrelatedinformationrelevant to modular fixture design and assembly/disassembly. The following eight function faces are defined as assembly featuresoffixtureelements: supportingfaces, supportedfaces, locating holes, counterbore holes, screw holes, fixing slots, andscrewbolts. Besidestheinformation aboutthefeaturelike typeanddimension, otherparameters, i.e. therelativeposition andorientationofthe featureintheelements localcoordinate system are recorded with the geometric model in the fixture element database. When one element assembles with another, the information aboutthematedfeatures isretrieved andused to decide the spatial relationship ofthe two elements. More information about the assembly features and their mating relationship arediscusseddetailedinRef 1. D. Constraintbasedfixtureassemblyin VE 1)Assemblyrelationshipbetweenfixtureelements Mating relationships have been used to define assembly relationships between part components in the field of assembly. According to the assembly features summarized in the above section, there are fivetypes ofmating relationships between fixture elements. Namely against, fit, screw fit, across, andT-slotfit,which are illustrated inFig. 5. Based on these mating relationships, we can reason the possible assemblyrelationshipofanytwoassembledfixtureelements. 2)Assemblyrelationshipreasoning Ingeneral, the assemblyrelationship oftwo assembledpart isrepresented as thematedassembly featurepairs ofthem. In the above section, we defined five basic mating relationships between fixture elements. Therefore, it is enabled to decide the possible assembly relationships through finding the possible mating assembly feature pairs. These possible assembly relationships are saved in assembly relationships database(ARDB)forfixtureassemblyinnextstage. However, when the fixture is complicated and the numbers ofcomposite fixture elements is large, the possible assembly relationships are too much to take much time for reasoning andtreating. To avoidthis situation, wefirstdecide the possible assembled elements pairs. That is to avoid reasoning the assembly relationship between a clamp andthe baseplate, for they never were assembled together. In this stage, some rules are utilized to find the possible assembled elementspairs. The algorithm of assembly relationships reasoning is similar to what discussed in Ref 12. Thus the detailed descriptionofthealgorithmisomittedfromthispaper. (a) AIlai.ns .2 l.I.F LIi I7 F d) Asicmie 1f-isxkt Elmn Fig. 5Fivebasicmatingrelationshipsbetweenfixtureelements 3)Constraint-basedfixtureassembly Aftercarrying outthe assemblyrelationships reasoning, all possible assembly relationships ofthe selected elements are establishedandsavedinARDB. Basedontheserelationships, the trainee can assemble these individual parts to a fixture system. This section is about the discussion of interactive assembly operation in VE. The process ofa single assembly operation is presented in Fig.5 and illustrated by two simple partsassemblyasshowninFig.6. In general, the assembly operation process is divided into three steps, namely assembly relationship recognizing, constraint analysis and applying, constraint-based motion. Firstly, the trainee selects an element and moves it to the assembled component. Once an inference between the assembling and assembled component is detected during the moving,the inferredfeatures is checked. Ifthetwo features is one of the assembly relationships in ARDB, they will be highlighted and will await the users confirmation. Once it is confirmed, the recognized assembly relationship will be appliedby constraint analyzing and solving, that is adjustthe translationandorientationoftheassemblingelementtosatisfy the position relationship ofthese two components, as well as applythenew constrainttotheassemblingelement.Whenthe new constraint is applied, the motion of the assembling element will be mapped into a constraint space. This is done bytransferring 3Dmotiondatafromtheinputdevicesintothe allowable motions ofthe object. The constraint-based motion notonlyensuresthattheprecisepositionsofacomponentcan be obtained, but also guarantee that the existing constraints will not be violated during the future operations. The assembling element will reach to the final position through succession assembly relationship recognizing and constraint applying. 2653 Ii 1-11 4- (b) F.t Authorized licensed use limited to: Nanchang University. Downloaded on December 20, 2009 at 22:44 from IEEE Xplore. Restrictions apply. NO Assembly relationship Iis possible checking elatioohship? Fig. 6Processofassemblyconstraintestablishment No V. MACHINING SIMULATION A. Manufacturinginteractions During the machining process, there are many types of manufacturing interactions associated with the fixture may occur. These interactions can be divided into two broad categories illustrated below, namely static interactions and dynamicinteractions. 1) Static interactions refer to the interference between fixture components, the interference between fixture components and machine tool, and the interference between fixture components andmaching feature ofworkpiece during theworkpiecesetup. 2)Dynamicinteractionsrefertothetool-fixtureinteractions, which occur within a single operation when the tool and the fixtureusedinthatoperationmaycollideduringcutting. Generally, the aspects of machining process and cutter paths are not considered duringthe fixture design stage. As a result, these interactions may often occur during the practical manufacturing. Thus the human machinists have to spend muchoftheirtimeidentifyingtheseinteractions andresolving them. Itis oftenresults inmodification orre-designoffixture system. Thatistediousandtimecostly. B.Interferencedetection Although the currently commercial software, like VERICUT, can simulates NC machining to detect tool path errors and inefficient motion prior to machining an actual workpiece. It is available to eliminate errors that could ruin the part, damage the fixture, break the cutting tool, or crash the machine during the part programming stage. However, these software are expensive and oriented to NC program- mertherebynotsuitableforfixturedesigners. During the fixture design stage, it should be ensured that the associated fixture interactions can be avoided. In this system, after the fixture configuration is complete, the machining simulation module is presented to the user to identifytheinteractionsandresolvethem. Within the machining simulation environment, the 3D digitalmodelofmachinetoolispresented. The canassemble the fixture components on the work bench and setup the workpiece, just as what the machining engineers do in the actual site. During the setup, the fixture components and the workpiece are move to their assembly position under manipulation. Theinterferencecheckingmoduleiscarriedout. Ifinterference occurs, the inferred objectwill be highlight. It is p
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