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黄河科技学院毕业设计（文献翻译） 第 16 页 可重构机器的设计原则摘要：可重构机器是围绕一些特殊产品零部件和机器结构可以快速变化而设计的新机类。它的机器结构可以根据生产需求的变化而发生变化。这种可重构机器的功能的变化和它的可扩展性，与产量或操作速度的变化有关。可重构机器是机器的新类，它填补了高度的灵活性、完全灵活机器高成本和低的灵活性、完全专用机低成本之间的空白。它是一个由可重构制造系统衍生出来，主要用于大批量生产线机器的设计方法，可重构机器的设计原则也遵循了类似的理念。本文介绍了可重构机器的设计原则，这可能被应用在不同领域的制造业。在这些设计原则的基础上，三种类型的可重构机床被设计并用于各类生产经营，如：加工，检验和装配。本文将展示在几个大型机器的原型设计和测试实验中，是如何利用这些设计原则的。关键词： 机械设计；可重构机器(RM)；可重构制造系统(RMS)；可重构机床(RMT)；可重构检查机(RIM)；可重构装配机(RAM)1 简介在中等和高容量配件的生产制造行业中，有两个主要传统的方法是专门制造系统（DMS）1，2和柔性制造系统（FMS）3-5。DMS是在部分产品要求产量高，能持续生产，而且这部分产品不会改变时使用。FMS是在所需的数量相对较低，这部分产品在设计中的有许多可预见的修改，或多个类型的产品在一个生产线上生产时使用。定制生产的一个创新方法，被称为可重构制造系统（RMS）6。对于一部分产品的零部件来说，这种新方法的主要优点是系统的定制灵活性比FMS投资成本低。RMS的心脏7具有一组核心特征：模块化，可扩展性，可积性，可兑换性，定制和诊断能力。在生产线上，一个典型的RMS包括传统的灵活机和被称为可重构机器（RM）的新型机器。通常，一般DMS是围绕一个大规模生产的特定产品所使用而设计的专用机。它的设计具有高可靠性、可重复性和高生产率，因此是相对简单，成本较低。而使用FMS设计的机器，可以以灵活的方式执行大多数操作。这些灵活的机器是用计算机控制（CNC），通过改变自己的计算机程序，可以完成许多不同的操作。由于大规模生产线的要求机器具有高可靠性，可重复性和高生产率，所以为大批量生产而设计的灵活机器都比较昂贵。相比之下，RM是可以设计定制灵活性，而这部分灵活性也正是这部分特殊产品零部件所需要的7。RM可以执行为特殊零部件预先设计的一套具有高可靠性，可重复性和高生产力的操作。所以由RM设计定制的灵活性，可以降低投资成本。另一方面，RM对产品的变化响应速度快，这都代表经济效益。RMS和它的六个核心特征的创新理念，最初是为大规模生产线而提出的。因为设计RM要求RMS理论体系不断完善，所以新的设计原则的也不断发展。这些机器上使用RMS，从而延长RMS概念，即从系统水平到机器水平。在文学上，几个机械设计的一般原则已经被提出和讨论。例如，Doubbel提出了具体化设计的原则，如：原则划分为任务，动力源和能量传输，以及安全性和可靠性等原则8。Norton定义工程设计原则为“提供各种方法技巧的程序和典型机器的科学设计原则，这些程序或系统要足够的详细，保证它能被了解”，而且还介绍了设计过程的各个阶段 9。SUH对工程使用的数学工具的设计进行深入的讨论，并举出机器设计的例子10。他提出了有关的功能要求矢量FR、设计参数DP和载体使用的矩阵A的设计方程。他使用这种方法去研究冗余设计和理想设计等不同的情况。其他研究人员的研究则主要集在用于制造业的机器的设计原则。 Altintas提出设计数控机床的基本原则11。它包括驱动电机选择标准，物理结构的配置和伺服控制的建模。Koren详细介绍了数控机床的设计原则12。13对加工系统的设计原则，以及一个可升级的多主轴RM的设计原则进行了讨论。在14中，研究了RM设计理念，对“模块化可重构机器”的目标进行研究与探讨。正如机械的模块化设计的主要特点，主要集中在分解，标准化和互换性。根据15，RMS的设计是基于建筑套件的原则，使其能够通过增加或去除机器系统去适应新的生产要求。一个设计可重构机床（RMT）的的综合方法16，17，通过输入的功能要求和流程计划，可以生成满足给定的要求规格的RMT。在18中，对具有RMS的机床的可扩展性进行深入研究和讨论。目前的研究重点是提高区域管理队的动态设计能力19和对RMT的伺服轴建模的模块化方法20。 RMT的伺服轴的设计和控制，可用于派生的机床模型。当生产高容量的部分时，需要一个用于测量几何尺寸公差以及表面质量的检测设备，但它应该具有响应快和成本低的特点。通常情况下，高精度和高重复性设计专用量具是昂贵的，而且这些量具只能针对单一的产品21。因此，制造商更倾向于使用柔性三坐标测量机（CMM），可以测量许多不同的零件22。通过一般的设计原则，SUH 10提出了一个有趣的的方法，可以应用机械零件的检验选择测量系统 23。利用这种方法，作者可以通过选择合适灵活性的CMM系统去完成自己的任务。本文的目的是介绍和解释RM的设计原则。遵循这些设计原则的前提下，提出的RMS理论的概念和发展6，7，并介绍一套完整实用的设计原则。这些设计原则的基础上，设计了几个RM。本文列举了机器的设计加工，检验和装配业务的三个例子。我们解释什么样设计原则能体现在每一台实际设计的机器上。金属切削，测量和装配代表不同的制造业务，然而，类似的设计原则已被用于设计这些操作的RM。两个全规模的RM原型建造（第3和第4条）。这些客户经理进行了实验测试，以评估他们的可重构特性以及其功能的表现。本文简要介绍了一些这些研究结果，希望读者能对我们的这些研究成果加以完善。第2节介绍并解释了RM的设计原则。第3，第4和第5分别描述了每个在第2节中所讨论设计原则的基础上设计的RM。首先是机器的简要说明，然后，在设计阶段的设计原则以及研究，并为每一台机器的应用进行了讨论。第6节总结本文，并提出结论性意见。2 设计原则RM是一个专门用来处理一些特殊产品零部件的变型机。一个RM好的设计是使得它精通操作的变化，并简化了转换过程。RM的设计原则遵循了可重构制造系统的理念。RM的设计主要应用于大规模生产。而且RM是为允许定制灵活性、经济效益生产和检查这些零部件而设计的。如果一台机器的设计遵循必要的原则和几个主要原则如下文所述，它将被列为一个RM。必要的原则：1、可重构机床是为特定产品零部件而设计的。主要原则：可重构机床可以定制灵活性。3、可重构机床可以方便和快速的变换其结构。4、可重构机床具有可扩展性：允许增加或删除元素，提高生产力或运作效率。5、 可重构机床的可以在生产线的几个地点使用相同的基本结构通过重新配置的机器结构来执行不同的任务。6、可重构机器的设计应采用模块化概念，即使用常见的“积木”和通用接口。阐明备注：1、第一个原则是一台机器定义为一个RM必要的条件。其他五个原则是关键原则，他们指定的是RM的本质。2、在原则1中产品零部件是一组具有类似特征的零件。一个特点是区分性质，例如材料，几何尺寸，形状或颜色。但相似性根据性质难以衡量。两部分可能有一组属性类似，但换一种思维，它们就存在其他不同点。当一些机械零件经过检查，合格品的几何形状是相同的。不同发动机的缸盖可能会被认为是同一类零部件。同样，几种类型的发动机缸体的也可能是同一类零部件。然而，发动机缸盖和缸体都相同的发动机可能不属于同一类零部件。在24中可能找到零部件的严格的定义和讨论。一类零部件在我们的上下文中的定义是广泛的，让每一个制造企业定义其自己的零部件，并设计一个根据其具体零部件所需要的RM。3、原则2中所提到的定制灵活性，这意味着一台机器仅拥有有限数量的灵活性，这些灵活性是设计说明书根据其功能所要求的。一般的灵活性是指一个单一的灵活机可以处理很多种类的产品，如在计算机数控（CNC）机床和通用坐标测量机（CMM）。4、第三个原则是“容易和快速变换”，要求其结构可以容易并快速的改变，可以快速增加或移除元素和快速设置时间。设计者应事先设计机器的快速重构方法。他或她应该决定如何快速找到紧固件和连接器，如何为不同的机器上设计几个可选择的位置，以及如何在自动化的控制过程中，不但速度在提高，而且保持它的精确性。5、原则5是指一个RM的基本结构设计的要求，即为了放置在沿生产线的不同位置可以允许其结构配置进行变换。各个配置的RM将在每个位置执行该位置的特定任务。换言之，原本相同的RM可能包括不同的结构，如主轴，传感器或夹持器以及不同的软件配置（硬件）。6、模块化设计是一个广泛的原则，一般好的机器设计惯例都用了这种做法。在我们的情况下，模块化应该让机器具有高效的可重构性。标准的电气，机械，控制和软件接口应该可以快速整合共同的元素，或事先设计或选择的“基石”。3 可重构机床（RMT）ERC/ RMS的研究人员提出机床的创新概念25和发展研究RMT的几个概念。其中两个已经建成，他们目前已经用于研究26，27。在本文中，我们将只集中在一台机器上，即“弓型RMT”27。3.1 弓型RMT的简要说明图1 弓型RMT弓型RMT的，如图1a所示，围绕一个产品零部件的倾斜的表面，例如在一些汽车发动机的缸体或缸盖。它为倾斜面的铣削和钻孔的大规模生产线而设计。机床可沿三个方向控制其自由度，沿主轴、沿纺锤轴和沿表轴。有一个额外的被动运动的主轴，根据在不同的倾斜面的加工角度，将主轴的角度位置可以分为五个预先设计的位置重新配置。因此，弓型RMT的是一种非正交的机器，每个机器的配置可能有不同的特点。根据这样一种方式，该机器可以设计成垂直于倾斜表面，然后再进行钻和磨。3.2 RM的设计原则，在弓型RMT的应用原则1 弓型RMT可以完成V6和V8汽车气缸头等带有倾斜面零件的加工，如图2所示。这些部件的制造过程中需要钻孔，攻丝或铣倾斜面。目前，典型的专用生产线，是专为一个特定零件的大规模生产。专用生产线上运行的机器，即是建立在一个特定的角度，执行的的单一操作，如铣或钻。弓型RMT的引进将改变专门的生产线为可重构生产线，这个生产线将完成不同的倾斜角度零部件的生产，而且无需更换机器。 图2 RMT部分厂家的2个汽车汽缸头：V8（左）和V6（右）原则2 弓型RMT的建成只是定制的灵活性。它的倾向角度可能从-15度开始，一次增加15度，直到最大45度，如图1b所示。原则3 弓型RMT的主轴从一个角度到另一个角度快速、便捷的变换，是通过机械化手段来控制，以保证其固定在准确的位置。当电机带动来主轴转动到所需的位置时，主轴定位块由螺栓附加到拱板，使其停止时更好的结构刚度和精度。 原则5 在生产线一个位置，弓型RMT能够在磨一个倾斜的表面，并在另一个位置，它可以对该平面进行铣，钻孔或攻丝。3.3 弓型RMT的设计研究和验证 RMT的设计阶段，我们主要关注的是将主轴从水平位置移动到45度的位置时，对机床的动态稳定性和性能有什么样的影响。机器制造好之后，RMT的动态特性要经过锤击试验和切削试验的验证18。这些实验结果经过分析后表明，机床的频率响应函数（法国法郎）的主频来自刀架总成，在600赫兹以上，无论主轴角位置。图3a显示在0和45度切割时机床的稳定性曲线。点“A”代表稳定条件下的切削，点“B”不稳定的状况。我们用点“A”和“B”表示参数，已经进行了切割实验。图3b显示，切削进给方向为水平方向时，稳定的加工过程中力量的快速傅立叶变换（FFT）。图3c显示FFT在水平方向切削进给时不稳定的情况下的力量。不稳定的切削过程中，约在650Hz时我们得到了一个清晰的信号，这个频率正对应着刀架的频率。在45度的倾角，重复类似切削实验结果表明有类似的特征。有趣的是，这些结果表明在机械结构进行重新配置，不影响弓型RMT的稳定性。图3 RMT动态特征除了在水平位置，弓型RMT是作为一个非正交机床的设计的。在设计阶段，设计理念和与此相关的控制问题进行深入研究28。有人提出一个新型的交叉耦合控制器。通过对控制系统的稳定性进行了研究，再模拟不同类型的控制器进行比较。弓型RMT的是专为快速和便捷的变换而设计的。移动主轴从-15的倾斜角度到45度，是对它能否固定在一个精确的位置进行了测试。在实验室中，它只需不到5分钟就完成的重新配置过程。弓型RMT在生产线的一个位置，可以在45度的倾斜表面上钻孔；而在另一个位置，另一台类似的弓型RMT的只是以不同的配置，就能够铣一个-15度的倾斜面。在设计阶段，有计划引入模块化的特点，通过使用标准接口，以便弓型RMT能够更容易变换主轴的位置。我们在这方面的努力没有成功，因为它需要和主轴供应商密切合作。在15中，机床主轴的接口模块化设计是一个突出的例子，其中的主轴有标准接口：电源，媒体，数据，对齐方式和工具的变化，这些都利用了 “多耦合”的概念和模块化原则。4重构检查机（RIM）4.1 简述可重构检验机（RIM）是为一些缸盖类零部件加工时，可以快速检查其性能而设计的。RIM最初开发时是用于测量几何特征，如发动机缸盖的顶面、结合面的平面度，平行度和轮廓度 29-31。根据不同的配置，不仅可以对几何特征进行检查，RIM也可以对缸盖表面的毛孔和其他表面纹理缺陷进行检查。RIM使用了商业激光传感器和高清晰度的线扫描相机，并结合计算机视觉技术和其他市场销售的非接触式传感器的非接触式测量方法。RIM的原型如图4a。在伺服驱动单轴运动阶段，通过配备了1微米的高精度线性规模的传感器沿直线轴视察的部分动作。按照议案阶段所需的采样密度和检验周期，以及探头采样频率进行检查。议案阶段沿轴向线性位置的每个测量点，检测速度变化对零件表面的精确度影响的映射记录。RIM一般在工业环境中使用。它位于相邻的加工生产线，包括部分转让的加工生产线，总周期时间一般被认为是大约40秒。无线电频率（RF）技术在实验室用于读取位于零件的夹具上射频标签并加以进行评估，以确定特定的零件编号。在完成测量和功能评价后，将评价结果存储在射频标签和RIM的数据库。博克图的RIM系统结构如图5。图4 可重构检查机图5 RIM系统结构4.2 RM的设计原则，在RIM的应用原则1，RIM是围绕一个发动机缸盖，在大规模生产的需要进行检查的部分零部件。属于这部分零部件的典型零件如图6。不同类型的发动机，它们的缸盖由不同的公司生产。然而，他们都有共同的特点，如平面的精密加工和一系列棱柱形状的螺纹孔。原则2， RIM只有定制的灵活性。机器是能够测量各种规格的气缸头的各种功能，但是它的设计不是用来衡量其中的一部分的所有功能，或来衡量是不相同的零部件的功能。 图6 部分厂家的发动机气缸头原则3，RIM可以快速和方便的变换其结构，在需要时，可以通过添加传感器或者通过改变现有传感器的位置，来达到同一零件的不同部位或不同的功能的检查的要求。原则4，RIM被设计成具有可扩展性的，即允许不同的探头安装在不同的地点。可扩展性可以高效测量不同的功能。原则5，RIM是能够在沿生产线的一个位置测量的表面平整度；在另一沿线的位置，测量两个功能之间的中心距离，如图7。图7 RIM的综合生产线4.3 RIM设计的研究和验证在本节中，我们展示了RM的设计原则及其对RIM设计的影响。此外，RIM作为一种非接触式检验机进行了实验验证。可重构检查机设计中心正如我刚才解释的发动机汽缸头的零部件。为了检测每个缸头，设计和使用了不同的装置。为了获取每一个缸头的所有性能，激光传感器的位置，以及视觉系统的位置都被重新配置。RIM可以测量立体几何的功能如：两个表面之间的平行度，表面之间的边缘距离和相关的三维特征之间的距离和表面平整度。然而，RIM的设计不能测量零件的圆柱度，因为气缸盖不检查圆柱度。我们已经用实验的方法测试了RIM的测量的质量。表1列出RIM的重复性实验测量参考的一部分测试结果。测量结果表明RIM的可重复性好。 表1 重复测量的部分参考值检查编号宽度平行平坦结合面平坦覆盖面1118,99.32118,98.83118,98.74118,98.55118,99.5平均值118,99.0重复性 (行)1.0单位是 m. (重复性定义为每行5个测试点所测得最大值和最小值之间的差值。)目前，坐标测量机（CMM），是工业的加工零件的检查标准工具。它采用了0.5至2.0毫米直径的球做触摸探头。RIM利用ConoProbe的传感器，它的激光束具有典型的20m的直径。因此，人们可能期待使用这两种类型的传感器与非完美的加工表面时出现不同的读数。为了比较RIM和坐标测量机（CMM）的测量结果，“虚拟球”的方法被开发和实施32。它诠释了非接触式激光测量，仿佛他们已通过CMM接触式探针进行测试。33中比较RIM和CMM测量和可重复性的结果。图4b显示了一个典型的的RIM结构的固定装置和可以自由变换的设计。设计包括一系列的螺纹孔，允许快速和容易的搬迁检查所需的各种传感器和配件。为了测量不同类型的缸盖的不同特点，我们已经改变传感器的装置和位置的许多次。当对不同缸盖进行测量师，一个典型的传感器改变其结构和位置所需的时间不到一个小时。传感器的校准过程后，RIM的重新配置过程34在实验室中成功地完成。图8 机器表面的孔为了证明该系统的可扩展性，RIM的测试用了不同数量的传感器。我们开始用两个激光传感器检验面平整度，后来我们增加了四个激光传感器进行测量 35。我们也在用机器视觉系统的行扫描相机的基础上，并用4 K和8万像素版本。我们可以使用的每个类型的传感器，单独或共同在缸盖表面进行扫描。视觉系统的一个重要的应用是测量表面缺陷，如铸造加工表面的毛孔36。如图8是一个典型的缸盖表面的毛孔。图8a显示了的边缘的一个孔，而图8b有一个“孤立的孔隙”。对于每个孔，我们可以分析其大小和位置与给定的资料的相比较。基于我们的孔隙率检测的研究，一个ERC/RMS工业合作伙伴，目前正在建设一个全面的机器生产线来取代目测的缸盖生产线。5 可重构装配机5.1 简述本文中所描述的可重构装配机（RAM）是研究汽车热交换器（散热器）37的组装机。Mehrabi博士和他的研究生进行了RAM的研究和概念设计。热交换器是长方矩阵，包括管和鳍头和侧面，如图9所示。装配过程，开始喂食管和鳍片核心建设者面积的。管是在栈的形式而鳍中包含每个散热片所需数量的托盘提供核心建设者喂。机器，然后把一个一个从各自的来源和过程迭代，直到达到所需数量的鳍和管翅片管。收集管和松散一起举行的鳍被称为“松散矩阵”。这种松散的基质，然后转移到总装区，在那里与方头封顶后，被压缩到正确的尺寸和对齐检查。管被压入提供的插槽，保证他们的对齐是相当重要的。被命名为“核心”从总装地区收到成品。之前的核心可以从装配区中删除，它是使用黄铜框架。一个框架的目的是要执行任务放置到装配夹具头和方支持。重构新框架设计，导致在最后的装配时间大幅减少。在图10提出的概念设计的核心。现有的组装机在各种产品之间几何特征的相似之处。在管与鳍片间组装数量大的热交换器需要一个更大的宽度在45到60秒之内。RAM的设计目标是减少装配时间到30秒，并允许利用可重构的设计原则属于相同的零件种类组装各类热交换器。 图9 热交换机图10 核心建设者5.2 RM的设计原则，在RAM中的应用原则1 设计了不同尺寸和不同数量的RAM。这是一个组装机，供汽车散热器生产厂家使用。许多不同类型的散热器，可以通过内存组装，鉴定和分类三个组定义“零件种类”37。本主题将在下一节中进一步解释。原则2 本机是专为灵活性定制的，因为它只能执行一些有关这些热交换器的组装任务。原则3 RAM是专组装不同尺寸的热交换器。如更换、回升和夹紧夹具，让不同类型和尺寸的产品组装。第6原则是RAM设计允许不同部位使用不同模块集成装机。热交换器的大小不同，拾取设备和模块化设计元素也不同。5.3 RAM设计的研究和验证以客户需要为出发点，RAM团队已经研究出了典型的核心技术。该小组负责研究这一核心技术的功能，试图了解它的局限性，并加以改进。这项研究得出的结论是由于转换时间的升高和周期的限制，因此，目标就是尽量减少转换时间，从而减少系统闲置状态。转换时间的影响，可以有效解决，使机器重构。如前所述，RMS是专门处理零件种类变化的一种设计，其模块化设计大大有助于减少转换时间。模块的互换，不需要许多调整，装配不同的产品时，RAM更换减少。RM设计的第一步是确定零件种类。使用产品目录，进行分类和分组，对产品功能进行研究，以建立一个与产品特性之间的关系。这些研究资料包括产品的功能，如型号，长度，宽度，高度，行数。利用这些关系来定义零件种类的特点，机器架构。这些关系得出的结论在最大程度上影响，长度和宽度是最重要的参数。表2 RAM的部分零部件子组长宽产品总数120202722020-32100320-30 1/220219次品45作为这项研究的结果38，三种主要的子组定义RAM的一类零件，一些不合格产品在表2中列出。与新结构的一零件种类，所需模块的数量已减少到三个，其中每一个需要照顾的一个子组，但仍超过90的产品范围覆盖。如果模块的设计是根据这零件而定义的，由此产生的问题，无需转换所有产品子组内的变化，如果零件种类变化，转换将 成另一变化模块。因此，可避免延长转换时间，导致大量的停机时间。这是一个很好的例子，改变整个零件的设计。RAM的设计原则和研究没有实验验证。6 总结和结论本文概述了RMS设计原则的重要性。基于本文提出的设计原则，RMT及RIM专利也得以实现25,29。RMS的每一种功能都依赖于不断的测试实验，以及完善的操控功能。本文就是以此作为研究的平台。本文主要贡献如下：- RMS表明RMS的设计原则可以应用到机械设制造系统。- 这些原则一般应用在各种生产领域，如加工，装配和计量。- RMS验证上述设计原则的重要性。- 研究表明RMS可重构性和良好的性能，用于RMS的设计原则。研究表明得出以下结论：- RMS代表一种用于大批量生产的新型机器。它弥补灵活机及专用机之间的不足。致谢笔者想感谢Y.Koren教授及参加RMT、RIM和RAM研究项目的研究员和毕业生们，感谢他们提供的相关资料。本论文在编写过程中，参考了V. Duphia和Dr. P. Spicer博士的研究成果和评论，以及美国密歇根大学NSF可重构加工系统工程研究中心提供的财政资助（NSF资助EEC95-92125），编者在此对他们一并表示感谢。Int J Adv Manuf Technol (2007) 34: 430439DOI 10.1007/s00170-006-0615-2ORIGINAL ARTICLEReuven KatzDesign principles of reconfigurable machinesReceived: 6 October 2005 / Accepted: 10 April 2006 / Published online: 8 June 2006# Springer-Verlag 2006Abstract Reconfigurable machines form a new class ofmachines that are designed around a specific part family ofproducts and allow rapid change in their structure. They aredesigned to allow changes in machine configurationaccording to changes in production requirements. Thereconfiguration may be related to changes in machinefunctionality or its scalability, i.e., the change in productionvolumes or speed of operation. Reconfigurable machinesrepresent a new class of machines that bridges the gapbetween the high flexibility and high cost of totally flexiblemachines and the low flexibility and low cost of fullydedicated machines. The design principles of reconfigu-rable machines follow a similar philosophy, which wasderived for reconfigurable manufacturing systems, andpresent an approach for the design of machines to be usedmainly in high-volume production lines. This paperintroduces design principles for reconfigurable machines,which may be applied in different fields of manufacturing.Based on these design principles, three types of reconfigu-rable machines were designed for various types ofproduction operations such as: machining, inspection andassembly. This paper shows how the suggested designprinciples were utilized in the design of several full-scalemachine prototypes and tested experimentally.Keywords Machine design.Reconfigurable machines(RM).Reconfigurable manufacturing systems (RMS).Reconfigurable machine tool (RMT).Reconfigurableinspection machine (RIM).Reconfigurable assemblymachine (RAM)AbbreviationsRM: Reconfigurable machine.RMS:Reconfigurable manufacturing systems.RMT:Reconfigurable machine tool.RIM: Reconfigurableinspection machine.RAM: Reconfigurable assemblymachine.DMS: Dedicated manufacturing systems.FMS:Flexible manufacturing systems.ERC/RMS: EngineeringResearch Center for Reconfigurable ManufacturingSystems.CNC: Computer numeric control.CMM:Coordinate measurement machine.FRF: Frequencyresponse function.FFT: Fast Fourier transform1 IntroductionThe two main traditional methods utilized by manufactur-ing industries in the production of medium- and high-volume parts are dedicated manufacturing systems (DMS)1, 2 and flexible manufacturing systems (FMS) 35.DMS is used when part production volumes are high andconstant, and the part does not change. FMS is used whenthe required quantities are relatively lower and manymodifications in the part design are foreseen, or more thanone type of product is produced on the same linesimultaneously. An innovative approach of customizedmanufacturing, termed reconfigurable manufacturing sys-tems (RMS) is described in 6. The main advantage of thisnew approach is the customized flexibility of the system toproduce a “part family” of products with lower investmentcost than an FMS. A set of core characteristics: modularity,scalability, integrability, convertibility, customization anddiagnosibility comprises the heart of an RMS 7. A typicalRMS includes both conventional flexible machines and anew type of machine called the reconfigurable machine(RM) on its production line.Typically, a dedicated machine used in a DMS isdesigned around a specific part that is mass produced. It isdesigned to perform a single operation with high reliabilityand repeatability, and high productivity and therefore isrelatively simple and less expensive. Machines that areused in an FMS are designed to perform most operations ina flexible manner. These flexible machines are computernumerical controlled (CNC) and can produce manydifferent parts by changing their computer programs.Since reliability, repeatability and high productivity areR. Katz (*)NSF Engineering Research Center for ReconfigurableManufacturing Systems, University of Michigan,Ann Arbor, MI, USAe-mail: Tel.: +1-734-7630956Fax: +1-734-6150312required for mass production lines, flexible machinesdesigned for high volume production are relativelyexpensive. In contrast, the RM is designed for customizedflexibility, i.e., the flexibility needed to produce a particularpart family 7. The RM can perform a pre-designed set ofrequired operations as specified for the specific part familywith high reliability, repeatability and high productivity.The limited, customized flexibility allows reduction ofinvestment costs on the one hand and fast response when aproduct changes on the other, both representing economi-cal benefits.The innovative idea of RMS and its six core character-istics was originally developed for “systems”, namely,mass production lines. Development of new designprinciples based on RMS philosophy was required inorder to design RMs. These machines are to be used onRMS lines, thereby extending the RMS concept from asystem level to the machine level.In the literature, several general principles of machinedesign have been proposed and discussed. For example,Doubbel describes principles of embodiment design suchas: principle of division of tasks, force and energytransmission, as well as safety and reliability principles8. Norton defines engineering design as “The process ofapplying the various techniques and scientific principlesfor the purpose of defining a device, a process or a systemin sufficient detail to permit its realization” and alsodescribes the phases of the design process 9. Suh presentsa thorough discussion of the design process in engineeringusing mathematical tools and shows examples of machinedesign 10. He presents the design equation that relates thefunctional requirements vector FR to the design param-eters DP vector using the design matrix A. Using thisapproach, he studies different cases of coupled design,redundant design and ideal design. Other researchers focuson design principles of machines which are used primarilyfor manufacturing. Altintas presents fundamental princi-ples of designing CNC machine tools 11. It includessizing and selecting drive motors, configuration of physicalstructure and modeling of servo control. Design principlesof CNC machine tools were also presented in detail byKoren 12. Design principles of machining systems aswell as an upgradeable multi spindle RM are discussed in13. RM design concepts are studied in 14 with the goalof developing “modular reconfigurable machine”. Asstated there, the key characteristics of modular machinedesign were focused on decomposition, standardizationand exchangeability. According to 15, the design of RMSis based on a construction kit principle that enables it toadjust to new production requirements by substitution,addition or removal of machine systems. A synthesismethodology for designing reconfigurable machine tools(RMT) 16, 17 takes a set of functional requirements and aset of process plans as the input and generates a set ofkinematically viable RMTs to meet the given specifica-tions. A thorough study of machine tools scalability in thecontext of RMS is presented and discussed in 18. Currentstudies are focused on improving dynamic design ca-pabilities of RMTs 19 and on a modular approach forRMT servo axis modeling 20. The derived machine toolmodels can be used for design and control of RMT servoaxes. When high volumes of parts are produced, there is aneed for rapid and low cost inspection equipment formeasuring geometrical and dimensional tolerances as wellas surface quality. Typically, dedicated gages that aredesigned for high precision and high repeatability areexpensive and are not flexible to product changes 21.Therefore, manufacturers prefer using flexible coordinatemeasuring machines (CMM) that can measure manydifferent parts or features 22. An interesting applicationof the general design principles proposed by Suh 10demonstrates a methodology for selecting a measuringsystem for inspection of mechanical parts 23. Utilizingthis methodology, the authors selected a flexible CMM-based system for completing their task.The goal of this paper is to introduce and explain thedesign principles of RMs. These design principles followthe concepts and vision of the RMS philosophy presentedin 6, 7 and introduce a complete set of practical designprinciples. Based on these design principles, several RMswere designed. The paper presents three examples of suchmachines designed for machining, inspection and assemblyoperations. We explain how the design principles arereflected in the actual design of each machine. Metalcutting,metrologyandassemblyrepresentdifferentmanufacturing operations; however, similar design princi-ples have been used to design RMs for each of theseoperations. Two full-scale prototypes of RMs were built(Sections 3 and 4). These RMs were experimentally testedto evaluate their reconfigurability features as well as theirfunctional performance. The paper briefly describes someof these studies and refers the readers to more completedocumentation of our research efforts.Section 2 presents and explains the design principles ofRMs. Sections 3, 4 and 5 describe each RM that wasdesigned based on the design principles discussed inSection 2. First a brief description of the machine isprovided. Then, the application of the design principlesduring the design phase as well as the studies andvalidation performed for each machine is discussed.Section 6 summarizes the paper and presents concludingremarks.2 Design principlesAn RM is a machine that is specifically designed to handleproduct variants within a specific part family. A gooddesign of an RM is a design that makes it proficient inhandling changes and simplifies the changeover procedure.The design principles of RMs follow the philosophy ofreconfigurable manufacturing systems. RMs are designedmainly for mass production applications. RMs are designedto allow customized flexibility and a cost-effectiveproduction and inspection of a family of parts.A machine is classified as an RM if its design follows thenecessary principle and several of the primary principlesstated below.431Necessary principle:1.A reconfigurable machine is designed around aspecific part family of products.Primary principles:2.A reconfigurable machine is designed for customizedflexibility only.3.A reconfigurable machine is designed for easy andrapid convertibility.4.A reconfigurable machine is designed for scalability:allows addition or removal of elements that increaseproductivity or efficiency of operation.5.A reconfigurable machine is designed to allowreconfiguration of the machine to operate at severallocations along the production line performing differ-ent tasks at different locations, using the same basicstructure.6.A reconfigurable machine should be designed applyingmodularity concepts, namely, using common “buildingblocks” and common interfaces.Clarifying remarks:1.The first principle is necessary in defining a machine asa RM. The other five principles are the key principlesthat specify the essence of RMs.2.Part family, in principle 1, is a set of parts with similarcharacteristics. A characteristic is a distinguishableproperty of a part e.g. material, geometry, shape orcolor. Similarity can be difficult to measure dependingon the property. Two parts can be similar based on oneset of properties, but different when a second set isconsidered. When machined parts are considered, thechoice of geometric and shape properties is common.Cylinder heads for different engines may be regarded apart family. Similarly, several types of engine blockscan form a part family. However, a cylinder head andan engine block of the same engine may not belong tothesamepartfamily.Rigorousdefinitionsanddiscussion of part families can be found in 24. Thedefinition of a part family in our context is broad toallow each manufacturing business to define its ownpart family and design a RM according to its specificneeds.3.Customized flexibility, mentioned in principle 2,means that a machine possesses only a limited amountof flexibility related to several specific features asrequired from the design specifications. General flex-ibility means that a single flexible machine can dealwith a large variety of features such as in a computernumerically controlled (CNC) machine tool or in ageneral-purposecoordinatemeasurementmachine(CMM).4.The third principle of “easy and rapid convertibility”suggests that the configuration should be designed toallow easy and fast change of machine elements, rapidaddition or removal of elements and quick set up time.The designer should design means for rapid reconfig-uration of the machine in advance. He or she shoulddecide how to allow fast access to fasteners andconnectors, how to design several optional locationsfor different machine elements and how to automatethe process in order to speed it up and keep it precise.5.Principle 5 refers to the requirement that the basicstructural design of a RM will allow changeableconfigurations in order to place the machine atdifferentlocations along the production line. At each locationthe RM will be configured to perform specific tasksthat are required for that location. In other words thesame basic RM may include different structural(hardware) elements such as spindles, sensors orgrippers as well as different software configurations.6.Design for modularity is a broad principle related to thegood practice of machine design in general. In ourcontext, modularity should allow efficient reconfigu-rability of the machine. Standard electrical, mechani-cal, control and software interfaces should allow rapidintegration of common elements or “building blocks”which were designed or selected in advance.3 Reconfigurable machine tool (RMT)The researchers at the ERC/RMS suggested an innovativeconcept of a machine tool 25 and developed and studiedseveral RMT concepts. Two of them have been built,demonstrated and are currently used for research 26, 27.In this paper we will focus on one machine only, the “archtype RMT” 27.3.1 Brief description of the arch type RMTThe arch type RMT, shown in Fig. 1a, was built around apart family of products with inclined surfaces, which existin some automotive engine blocks or cylinder heads. It wasdesigned for a mass production line for both milling anddrilling on inclined surfaces.The machine tool has three controlled degrees offreedom along its column, along the spindle axis andalong the table axis. One additional passive motion is theangular reconfiguration motion of the spindle, whichallows reconfiguring the spindles angular position intofive pre-designed locations to allow machining on differentinclined surfaces. Therefore, the arch type RMT is a non-orthogonal machine that may have different characteristicsat each configuration of the machine.The machine is designed to drill and mill on an inclinedsurface in such a way that the tool is perpendicular to thesurface.3.2 Application of RM design principles in arch typeRMTPrinciple 1 The arch type RMT was built for a part familywith inclined surfaces found in V6 and V8 automotivecylinder heads shown in Fig. 2. During manufacturing of432these parts there is a need for drilling, tapping or millingon inclined surfaces. Currently, typical dedicated produc-tion lines are designed for mass production of one specificpart. The machines that operate on dedicated lines arededicated as well, i.e. are built at one specific angle andperform a single set of operations such as milling ordrilling. The introduction of the Arch Type RMT willallow changing a dedicated production line to a reconfig-urable line that will allow production of a family of partswithdifferentinclinationangleswithoutreplacingmachines.Principle 2 The arch type RMT was built for customizedflexibility only. The inclination angle might be changedbetween 15 degrees up to 45 degrees in steps of 15degrees as shown in Fig. 1b.Principle 3 The arch type RMTwas designed for rapid andeasy convertibility by moving the spindle from one angleto another by means of a motorized mechanism and byfixing it at a precise location. When the motor brings thespindle to its required location the spindle is rested onpositioning blocks that are attached to the arch plate andbolted to have better structural rigidity and precision.Principle 5 At one location along the production line, thearch type RMT is capable of milling on an inclined surfaceand at another location, it is capable of drilling or tapping.3.3 Study and validation of arch type RMT designOur key concern at the design phase of the RMT was thedynamic stability of the machine tool and how theperformance will be affected by moving a large mass ofthe spindle from horizontal location to 45 degrees location.Once the machine was built, dynamic characteristics of theRMT were experimentally validated using hammer testsand cutting tests 18. It was shown after analysis of theseexperimental results that the dominant frequency in themachines tool frequency response function (FRF) camefrom the tool holder assembly, at above 600 Hz., regardlessof spindle angular position. Figure 3a shows analyticallyderived stability lobes for cutting at 0 and 45 degrees. Point“a” represents stable cutting conditions and point “b”unstable conditions. We have performed cutting experi-ments using the parameters indicated by points “a” and“b”.Figure 3b shows the fast Fourier transform (FFT) of cuttingforce in feed direction during stable machining inhorizontal position. Figure 3c shows the FFT of cuttingforce in feed direction during unstable machining also in ahorizontal position. During unstable cutting, we get a clearsignal around 650Hz which corresponds to the tool holdermode. Similar cutting experiments were repeated at 45degreesinclinationandtheresultsshowedsimilarcharacteristics. The results interestingly showed that thereconfiguration of machine structure does not affect archtype RMT stability.The arch type RMT was designed as a non-orthogonalmachine tool, except when in horizontal position. At thedesign phase, a thorough study of the control problemassociated with this design concept was performed 28. Anew type of cross-coupling controller was suggested. Thestability of the control system was investigated, andFig. 1 Arch type RMTFig. 2 RMT part family two automotive cylinder heads: V-8 (left)and V-6 (right) 26433simulation was used to compare different types ofcontrollers.The arch type RMT was designed for rapid and easyconvertibility. The process of moving the spindle from 15degrees angle to 45 degrees by means of a motorized linearstage and fixing it at a precise location was tested. It takesless than 5 min to complete the reconfiguration process inthe laboratory.The arch type RMT is capable of drilling on a surfacewith 45 degrees inclination at one location along theproduction line and another similar arch type RMT justdifferently configured is capable of milling on a surfacewith 15 degrees inclination in a different location.In the design phase there was a plan to introducemodularity features to the Arch Type RMT by usingstandard interfaces in order to enable easy spindlesexchangeability. We have not succeeded in this effortsince it required close cooperation with spindles supplier.An outstanding example of modular design of spindleinterfaces for machine tools is presented in 15, where thespindle has standard interfaces for: power, media, data,alignment and tool change that allowed the development ofthe “multi coupling” concept that utilizes modularityprinciples.4 Reconfigurable inspection machine (RIM)4.1 Brief descriptionThe reconfigurable inspection machine (RIM) was de-signed for rapid, in-process, inspection of the machinedfeatures of a part family of cylinder heads.The RIM has been originally developed for measuringgeometric features such as: flatness, parallelism and profileassociated with the cover and joint faces of an enginecylinder head 2931.Under a different configuration, by adding a machinevision system to the structure, the RIM also allowsinspection of cylinder head surfaces for pores and othersurface texture imperfections.The RIM uses non-contact measurement methods basedon commercial laser sensors and high-definition line-scancameras in conjunction with computer vision technologyand other commercially available non-contact sensors. Aprototype of the RIM is shown in Fig. 4a.The inspected part moves along a linear axis and passesthe sensors on a servo-driven single-axis motion stage thatis equipped with a high-precision linear scale of 1 maccuracy. The velocity of the motion stage, as well as theprobe sampling frequency, can be varied in accordance toFig. 3 RMT dynamic characteristicsFig. 4 Reconfigurable inspection machine434the required sampling density and inspection cycle time.The linear position along the axis of travel is recorded foreach measurement point, which enables a precise mappingof the part surface without being affected by variations inthe motion stage velocity.The RIM is intended for use in an industrial environ-ment. It is located adjacent to the machining line with atotal cycle time including part transfer equal to that of themachining line, which is assumed to be around 40 seconds.Radio Frequency (RF) technology was demonstrated in thelaboratory for reading the RF tag located on the part fixtureto identify the specific part number to be evaluated. Uponcompletion of the measurements and feature evaluations,the results of the evaluation were stored on the RF tag andon the RIM database. A bock diagram of the RIM systemarchitecture is presented in Fig. 5.4.2 Application of RM design principles in RIMPrinciple 1 The RIM was built around a part family ofengine cylinder heads that during mass-production needin-line inspection. Typical parts that belong to this partfamily are shown in Fig. 6. These engine cylinder headswere produced by different companies for different typesof engines. However, all of them have common charac-teristic features such as precisely machined flat surfaces,prismatic shape and a series of threaded holes.Principle 2 The RIM was built for customized flexibilityonly. The machine is capable of measuring variousfeatures of cylinder heads of various sizes; however, it isnot designed to measure all features of one part or tomeasure other parts that are not from the same part family.Principle 3 The RIM is designed for rapid and easyconvertibility by adding sensors when needed and bychanging the location of existing sensors as required forinspection of different parts or different features of thesame part.Principle 4 The RIM was designed to be scalable, i.e., toallow mounting of different probes at different locationsprepared at the outset. The scalability enables efficientmeasurements of different features.Principle 5 The RIM is capable of measuring surfaceflatness at one location along the production line andmeasuring distance between two features centers atanother location along the line as presented schematicallyin Fig. 7.4.3 Study and validation of RIM designIn this section, we demonstrate the RM design principlesand their implementation as reflected in RIM design. Also,RIM performance as a non-contact inspection machine wasexperimentally validated.The reconfigurable inspection machine was designedaround a part family of engine cylinder heads as explainedearlier. To measure each of the heads, different fixtureswere designed and used. For each head, the location of thelaser sensors as well as the position of the vision systemwere reconfigured to capture all features of interest.The RIM can measure geometrical and dimensionalfeatures such as: flatness of a surface and parallelismbetween two surfaces, distance between surfaces distancebetween edges and related dimensional features. The RIMis not designed, however, to measure the roundness ofparts, since roundness is not relevant for inspectingcylinder heads, which are prismatic parts. We have testedexperimentally the quality of RIM measurements. Table 1presents RIM repeatability experimental results tested innominal condition when measuring a reference part. Themeasurements show good nominal repeatability of theRIM.Currently,thecoordinatemeasurementmachine(CMM), is the standard tool for industrial inspection ofmachined parts. It uses a touch-probe with a 0.5 to 2.0-mmdiameter ball. Utilizing the ConoProbe sensor on RIM, itslaser beam has a typical diameter of 20m. Therefore, onecan expect different readings when using these two types ofsensors on machined surface with a non-perfect surfacefinish. In order to compare RIM measurement results withthe results of a coordinate measurement machine (CMM),the “virtual ball” method was developed and implemented32. It provides the interpretations of non-contact lasermeasurements as if they have been performed by a CMMtouch-probe. A comparison between measurements fromthe RIM and a CMM, and repeatability results from theRIM are presented in 33.Figure 4b shows a typical design-for-convertibility ofthe RIM structure and fixtures. The design included a seriesFig. 5 RIM system architectureFig. 6 RIM part family of engine cylinder heads435of threaded holes to allow fast and easy relocation ofvarious sensors and accessories needed for inspection.While measuring different features on different types ofcylinder heads, we have changed the fixtures and thelocation of the sensors many times. A typical time periodrequired for relocation of sensors when different heads aremeasured is less than an hour. The calibration process ofthe sensors following reconfiguration process of the RIM34 was successfully tested in the laboratory.To demonstrate scalability of the system, the RIM wastested with a differing number of sensors. We started withtwo laser sensors for surface flatness inspection and weincreased the number of laser sensors to four whenmeasuring parallelism 35. We also applied machinevision systems based on a line scanning camera and usedboth the 4 K and 8 K pixels versions. We could use eachtype of sensor separately or together in parallel during thescan of the cylinder head surface. One important applica-tion of the vision system was measuring surface defectssuch as casting originated pores on machined surfaces 36.A typical image of pores on cylinder head surface is shownin Fig. 8. Figure 8a shows a pore which is connected to anedge of a machined feature while Fig. 8b presents an“isolated pore”. For each pore of interest we can analyze itssize and the location relative to some given datum. Basedon our porosity inspection research, one of ERC/RMSindustrial partners is currently building a full-scale machineto be located and used on a production line of cylinderheads replacing visual inspection.5 Reconfigurable assembly machine5.1 Brief descriptionThe reconfigurable assembly machine (RAM) described inthis paper is an assembly machine for automotive heatexchangers (radiators) 37. Dr. M. Mehrabi and hisgraduate students have conducted a study and conceptuallydesigned the RAM together with an ERC/RMS industrialpartner.Heat exchangers are rectangular matrices comprisingtubes and fins bordered by headers and side supports asshown in Fig. 9. The assembly process starts by feedingtubes and fins to the core-builder area. The tubes are in theform of stacks that are fed into the core-builder whereas thefins are supplied in trays that contain the required numberof fins per radiator. The machine then places one tubefollowed by one fin from the respective sources and theprocess iterates till the required quantity of fins and tubes isreached. The collection of tubes and fins that are looselyheld together is termed as a loose matrix. This loosematrix is then transferred to the final assembly area where itis capped with side supports and headers after beingcompressed to the correct dimensions and checked foralignment. The tubes are to be pressed into the slotsprovided in the headers and therefore their alignment isfairly important. The finished product received from thefinal assembly area is termed as the core. Before the corecan be removed from the assembly area, it is constrained byFig. 7 RIM integration onproduction lineTable 1 Repeatability measurements performed on a reference partInspection numberWidthParallelismJoint face flatnessCover face flatness1118,99.32118,98.83118,98.74118,98.55118,99.5Mean value118,99.0Repeatability (range)1.0Values are in m. (Repeatability is defined as the difference between the max and min values in the range defined by the five inspectionsperformed)436the use of brass frames. A new pick and place mechanismwas designed to perform the task of placing the headers andside supports into the assembly fixtures. The design of thenew reconfigurable pick and place mechanism led todrastic reduction in final assembly time. The conceptualdesign of the core-builder is presented in Fig. 10.The similarities between various products are based ongeometrical features. A greater width results in a greaternumber of tubes and fins. An existing assembly machinecan assemble heat exchangers in 45 to 60 s. The designgoal of the RAM was to reduce assembly time to 30 s andallow assembly of various types of heat exchangers thatbelong to the same part family utilizing reconfigurabledesign principles.5.2 Application of RM design principles in RAMPrinciple 1 The RAM was designed around a part familyof heat exchangers with different dimensions and differentnumbers of fins and tubes. It is an assembly machine usedby automotive radiators manufacturers. Many differenttypes of radiators, which could be assembled by RAM,were identified and classified into three main groups thatdefine the “part family” 37. This topic will be furtherexplained in the next section.Principle 2 The machine was designed for customizedflexibility as it can perform only some of the assemblytasks related to core-building of these heat exchangers thatbelong to the defined part family.Principle 3 The RAM was designed for rapid convert-ibility to allow the assembly of different sizes of heatexchangers. Replacing the automated core builder ele-ments such as the pick and place mechanism and the loosematrix grippers, allows assembly of different types andsizes of products.Principle 6 The RAM was designed to use differentmodules or building blocks that are integrated into theassembly machine to allow the assembly of different parts.Modular elements of pick and place devices and gripperswere designed for different sizes of heat exchangers.5.3 Study and validation of RAM designThe RAM team has studied the characteristics of a typicalcore-builder that our industrial partner has designed andFig. 9 Heat exchanger 37Fig. 10 The core-builder 37Fig. 8 Porosity on machined surfaceTable 2 RAM-part family 25SubgroupsLengthWidthTotal products1202027220203210032030 1/220219rejected45437built for its customers. The team investigated this core-builders functionality and tried to understand its limita-tions and improve them.The study led to the conclusion that the productivity ofthe existing core-builder is constrained by elevatedchangeover and cycle times. Therefore, the goal was tominimize changeover time and hence reduce the idle stateof the system. The constraint to productivity formed by thechangeover time can be addressed effectively by makingthe machine reconfigurable. As previously stated, RMs arespecifically designed to handle changes within a partfamily. Their modular design significantly contributestowards the reduction in changeover time. The change-overs in RAM are reduced to the interchanging of modulesinstead of the many adjustments needed in the existingassembly machines, when assembling different products.The first step in the design of a RM is a clearidentification of the part family. Using our industrialpartners products catalog, 398 radiators were classifiedand grouped. Combinations of product features werestudied in order to establish a relationship between theproduct characteristics. The information for this studyconsisted of product features such as model, length, width,height, number of rows and car that uses it. Theserelationships were utilized to define part families depend-ing on the characteristics that are more imperative tomachine architecture. The study of these relationshipsconcluded that the length and the width are the mostimportant parameters that affect the reconfigurability of themachine to the greatest extent.As a result of this study 38, three main subgroupsdefine the RAM part family, and a few rejected productswere identified as listed in Table 2. With the newlystructured part family, the number of required modules hasreduced to three; each of them takes care of one sub group,whereas still more than 90% of the product range wascovered. If the design of the modules is based on this partfamily definition then the resulting machine will handlechanges within product sub group without requiringchangeover at all, and if the change is across a part familythen the changeover will be restricted to a change of amodule. Hence, extended changeover time that leads tolarge downtimes, can be avoided. The easy changes acrossthe part family represent a good example of design forconvertibility. The design principles and the study of RAMwere not validated experimentally since the machine wasnot built.6 Summary and conclusionsThis paper outlines the importance of design principles forRMs. Based on the design principles presented in thispaper, the ideas presented in the RMTand RIM patents 25,29 were realized. Each of the full-scale RMs wasexperimentally tested for the validation of reconfigurationprinciples as well as for sound functional performance. Theprototypes described in the paper currently serve asresearch platforms.The main contributions of this paper are as follows:The RMS vision was refined into concrete machinedesign principles for the design of RMs that can beused in a manufacturing system.The generality of application of these principles wasdemonstrated in various manufacturing domains suchas machining, assembly and metrology.The importance of the aforementioned design princi-ples was validated for RMs.Studies that demonstrate reconfigurability and goodperformance of the RMs that used the design principlesfor RMs were presented.The conclusions of our study are as follows:RMs represent a new class of machines that aredesigned mainly for high-volume production applica-tions. They bridge the gap between the flexiblemachines and the dedicated machines.Not all design principles presented in this paper mustbe reflected in the design of each specific RM.However, the principle of a machine that is designedaround a part family is a necessary condition andshould be reflected in the design.The design principles were demonstrated in the designof reconfigurable machining, inspection and assemblymachines; however, this philosophy is general and maybe applied to other domains of machine design.The design principles of RMs and RMS follow asimilar philosophy.RMs enable production of different products thatbelong to the same part family by allowing rapidand efficient pre-designed changes of a machinesconfiguration.The design principles of RMs are focused mainly onthe functionality of these machines and are importantin the phase of conceptual design. The detailed designof a RM follows concepts similar to any other machinedesign.The suggested design principles do not contradict anytraditional design principles related to the goodpractice of machine design.AcknowledgementsThe author would like to thank Prof. Y. Korenfor his RMS vision and his remarks to this paper and to the teams ofresearchers and graduate students who participated in the RMT, RIMand RAM projects. The author would like to thank V. Srivatsan, J.Duphia and Dr. P. Spicer for their feedback and remarks to this paper.The author also gratefully acknowledges the financial support of theNSF Engineering Research Center for Reconfigurable MachiningSystems (NSF Grant EEC95-92125) at the Univers