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毕 业 设 计（论 文）任 务 书1本毕业设计（论文）课题应达到的目的： 培养学生综合运用所学的基础理论、专业知识和专业基本技能结合实际独立完成课题的能力；提高其专业英语水平，计算机运用水平及书面及口头表达能力；训练其初步工程设计的能力，为顺利走向相关专业工作岗位打下基础。 2本毕业设计（论文）课题任务的内容和要求（包括原始数据、技术要求、工作要求等）： 食品搅拌机主要作用是将食品搅拌均匀，有时还需要进行加热，此外还应考虑搅拌完成后的倒料、清洗、设备所占用的空间大小、结构的简单可行等问题。针对中粘度的物料进行设计，既要考虑横向搅拌，又要考虑纵向的混合，主要包括总体设计；传动装置设计；筒体、搅拌轴和卸料机构设计等毕 业 设 计（论 文）任 务 书3对本毕业设计（论文）课题成果的要求包括图表、实物等硬件要求： 1.外文参考资料及译文（附原文）；2.毕业设计开题报告一份；3.编写设计说明书一份；4.完整的设计图纸一套。 4主要参考文献： 1koutmos,p,McGuirk,JJ,CFD Predictions of Lobed Mixer puter Methods in Applied Mechanics and Engineering,1995,122;131-1442Eckerle, W A,Sheibani, H , Awad, J ,Experimental Measurement of the Vortex Development Downstream of a Lobed Forced Mixer, American Society of mechanical Engineers,paper 90-gt-27,19903冯忠绪，李彰，王卫中，等. 搅拌臂数目与搅拌叶片的面积J. 工程机械，2008，39 （2）：61-694赵健，李刚. 双卧轴强制式搅拌机物料运动的分析模拟J. 机电产品开发与创新，2009，23（1）：66-675 赵利军，冯忠绪，双卧轴搅拌机搅拌装置的改进与实验J，中国工程机械学报，2004，2（3）25-296闫景凤，刘希峰，张海春，9JLT -10 型卧式搅拌机结构解析J，农机化研究，2010，第5期，64-677刘兴华，张帆，卧式双螺旋搅拌机的设计及原理J，煤矿机械，2000，第9期，10-118张继良.摆动式搅拌器的设计M.石油化工设备技术，1994（15）：41-449王传志、陈玲、何红生.卧式搅拌缸的制造J.制造与安装，2004（4）：37-4910林兴华、胡锡文、刘海洋、周本浩.糖化锅的搅拌与传热研究M.啤酒科技，2005（11）：20-2311曾祥平，王治平，双轴搅拌机的几点改造及自制J，水泥CEMENT，2007（1），65-6612苏峰.油脚锅搅拌装置的改进方法J中国油脂，1998（23）：5-713龚鹤星.真空搅拌结晶锅再浓缩过程中常见的问题J.发酵科学通讯，1992（21）4-614王凯，虞军. 搅拌设备M.北京：化学工业出版社，2004.4:139-16315袁巧霞，任奕林.食品机械使用维护与故障诊断M.北京：机械工业出版社，2009.4:125-13716肖振金，翁明辉等.食品工厂机械与设备M.北京：轻工业出版社，1991.4:110-117 毕 业 设 计（论 文）任 务 书5本毕业设计（论文）课题工作进度计划：2015.12.16- 毕业实习调研，完成开题报告、中英文翻译、论文大纲2016.3.19-2016.4.25 提交论文草稿，4月中旬中期检查2016.4.26-2016.5.6 提交论文定稿2016.5.6-2016.5.13 准备答辩2016.5.13-2016.5.26 答辩，成绩评定，修改完成最终稿 所在专业审查意见：通过负责人： 2016 年 1 月13 日 毕 业 设 计（论文） 开 题 报 告 1结合毕业设计（论文）课题情况，根据所查阅的文献资料，每人撰写不少于1000字左右的文献综述： 搅拌机理论上是指能够将任何状态（固、液、气或半液态）下的物料均匀的掺和在一起。搅拌机的运用是最为广泛之一的，它大量的应用于工业、农业、食品、医药等众多行业中。而食品搅拌机在我们日常生活中是必不可少的，它广泛应用于家庭、食品店和一些食堂等场所。在日常生活中，搅拌机在做糕点的食品店中用于和面，搅匀鸡蛋等。在一些大型企业、学校中，搅拌机则用来淘米。现有的机械设备中有卧式搅拌锅和立式搅拌机，卧式搅拌设备的缺点在于其占有的空间太大而且机构复杂，但是也有的搅拌物料多，设计简单，稳定性高等特点。在国内外食品搅拌机的研究上，搅拌机的外形各异，型号繁多，有各种通用的搅拌设备和专用的搅拌设备。搅拌机的分类方法很多，按搅拌机的桨叶机构可以分为平叶、折叶、弯叶、螺旋叶片搅拌机等；按安装结构又可以分为整体式和剖分式，对于大型设备，往往做成剖分式的，便于把搅拌机直接固定在搅拌轴上而不用拆除搅拌机的其他部件；按用途又可以分为低粘流体和高粘流体搅拌机；按流体的流动形态可以分为轴向流动搅拌机和径向流动搅拌机，有些搅拌机在运转时，流体既产生轴向搅拌又产生径向流的称为混合搅拌机。相比于国外的搅拌机则显的国外的搅拌机比较智能，使用的寿命也比较长。我国是一个人口大国，食物是人生活的必需品。食品搅拌机的合理设计可以提高食品加工的效率，并且可以节省劳动力。随着我国经济水平的提高，劳动密集型产业逐渐退出历史舞台，逐渐被自动化机械所代替。机械行业是一个即古老又散发出勃勃生机的行业，我国的机械行业比欧美日等发达国家差了一个档次，在轻工业机械设计上，我国的机械设计在效率和效果上都有着很大的差距。我们在吸取国外的先进技术和经验，努力进取，是我国的机械行业有一个质的飞跃！虽然搅拌机的种类比较多，但是一般的搅拌机都是有电动机、传动装置、搅拌轴、搅拌叶片、筒体、卸料机构、机架等组成的。传动装置包含了：带轮、减速机等。筒体有轴承座、轴承、端盖等。机架则主要包括锅体安装、控制面板、电器柜的安装等。由于搅拌机的飞速的发展，现在它已成为跨学科的、有众多应用领域的传统学科。据联合国欧洲经济委员会和国际搅拌技术联合会的统计。搅拌机在世界工业中占据很重要的地位，它以强劲的增长速度加快世界工业的自动化进程。随着工业自动化程度的提高，搅拌机将在更多的领域发挥更大的作用。参考文献1koutmos,p,McGuirk,JJ,CFD Predictions of Lobed Mixer puter Methods in Applied Mechanics and Engineering,1995,122;131-1442Eckerle, W A,Sheibani, H , Awad, J ,Experimental Measurement of the Vortex Development Downstream of a Lobed Forced Mixer, American Society of mechanical Engineers,paper 90-gt-27,19903冯忠绪，李彰，王卫中，等. 搅拌臂数目与搅拌叶片的面积J. 工程机械，2008，39 （2）：61-694赵健，李刚. 双卧轴强制式搅拌机物料运动的分析模拟J. 机电产品开发与创新，2009，23（1）：66-675 赵利军，冯忠绪，双卧轴搅拌机搅拌装置的改进与实验J，中国工程机械学报，2004，2（3）25-296闫景凤，刘希峰，张海春，9JLT -10 型卧式搅拌机结构解析J，农机化研究，2010，第5期，64-677刘兴华，张帆，卧式双螺旋搅拌机的设计及原理J，煤矿机械，2000，第9期，10-118张继良.摆动式搅拌器的设计M.石油化工设备技术，1994（15）：41-449王传志、陈玲、何红生.卧式搅拌缸的制造J.制造与安装，2004（4）：37-4910林兴华、胡锡文、刘海洋、周本浩.糖化锅的搅拌与传热研究M.啤酒科技，2005（11）：20-2311曾祥平，王治平，双轴搅拌机的几点改造及自制J，水泥CEMENT，2007（1），65-6612苏峰.油脚锅搅拌装置的改进方法J中国油脂，1998（23）：5-713龚鹤星.真空搅拌结晶锅再浓缩过程中常见的问题J.发酵科学通讯，1992（21）4-614王凯，虞军. 搅拌设备M.北京：化学工业出版社，2004.4:139-16315袁巧霞，任奕林.食品机械使用维护与故障诊断M.北京：机械工业出版社，2009.4:125-13716肖振金，翁明辉等.食品工厂机械与设备M.北京：轻工业出版社，1991.4:110-117毕 业 设 计（论文） 开 题 报 告 2本课题要研究或解决的问题和拟采用的研究手段（途径）： 研究的内容1. 搅拌机的总体结构；2. 电动机的选型；3. 传动比的分配；4. 减速器的选型；5. V带轮的设计、选择；6. 搅拌轴的设计；7. 叶片的设计；8. 轴承的设计；9. 筒体的设计；10. 卸料机构拟采用的研究手段：本课题针对横轴卧式搅拌机的设计，食品搅拌最重要的要求就是食品搅拌要均匀，并且要效率高。拟在在单轴的基础上改为双轴，利用减速机的双输出轴的旋向不同，搅拌轴上叶片对的螺旋角度使物料形成一个循环，在循环的过程中叶片的搅动有起到了挡板的作用，使混合更加杂乱无章，混合的更均匀，搅拌效率更高。毕 业 设 计（论文） 开 题 报 告 指导教师意见：1对“文献综述”的评语： 从“文献综述”看该生在做论文之前对相关资料进行了收集及查阅，对所要研究的对象及研究的步骤有了一定的认识。相信该生通过努力能顺利完成本次毕业设计。 2对本课题的深度、广度及工作量的意见和对设计（论文）结果的预测：本课题工作量、难度适中。课题具有一定的实际意义，相信通过本课题的研究，能设计出在性能符合实际应用的产品。3.是否同意开题： 同意 不同意 指导教师： 2016 年 03 月 06 日所在专业审查意见：同意 负责人： 2016 年 03 月 08 日译文题目： Reconfigurable Machine Tools 可重构机床 Reconfigurable Machine Tools R.G. Landers, B.K. Min, and Y. KorenUniversity of Missouri Rolla, Department of Mechanical Engineering, Rolla, Missouri University of Michigan, Department of Mechanical Engineering, Ann Arbor, MichiganAbstract The uniqueness of Reconfigurable Manufacturing Systems (RMSs) is that the structure of the system as well as of its machines and controls can be rapidly changed in response to market changes (demand and products). A major component of RMSs is the reconfigurable machine tool (RMT). By contrast to conventional CNCs that are generalpurpose machines, RMTs are designed for a specific, customized range of operation requirements and may be costeffectively converted when the requirements change. In this paper, systematic design tools that have been recently developed for RMTs are reviewed, and three examples are provided to compare RMTs to traditional types of machine tools. Keywords: Machine Tool, Machine Tool Module, Conversion 1 INTRODUCTION Traditionally, Dedicated Manufacturing Systems (DMSs) have been designed to produce a specific part. These systems are economical when the production volumes are high and the part is produced over a long period of time. Conversely, Flexible Manufacturing Systems (FMSs) are designed to accommodate a large variety of parts even though the parts are not specified at the system design stage. For an overview of FMSs, see 1. These systems are economical when the production volumes are low, and a large variety of parts are produced. Rapidly changing market demands have made traditional DMSs economically infeasible for many applications and have driven the use of FMSs. However, FMSs do not provide the robustness of DMSs and often have wasted resources making them uneconomical in many production situations 2. For many applications it is believed Reconfigurable Manufacturing Systems (RMSs) that combine the advantages of DMS and FMS will provide an economical solution 3. These systems are designed to accommodate a specific range of production requirements (i.e., product mix and volumes). Further, RMSs are characterized by customized flexibility, such that they are tailored to the current production requirements, but may be economically converted to a new set of production requirements. Thus, these systems are economical and robust since they are customized to the production requirements, their resources are minimized, and flexibility in their design allows for costeffective conversion when new production requirements arise. Indeed, reconfigurable manufacturing has been identified as one of the six grand challenges for competitive manufacturing in 2020 4. As production requirements for a machining system change, so will the operation requirements (i.e., features to be machined and cycle times) for an individual station. Major components that make RMSs feasible are reconfigurable machine tools (RMTs). These machine tools are costeffective because they are customdesigned for a given range of operation requirements, and can be economically converted to meet new requirements. A conceptual design of an RMT based on the patent of Koren and Kota 5 is shown in Figure 1. As the part size and features change, the spindles can be relocated to perform the same operation in a different location or replaced with another spindle to perform a different operation. Spindles can also be added or deleted such that the resources are optimized. Figure 1: Conceptual RMT 5. A common type of machine tool in large manufacturing industries today is the dedicated machine tool (DMT). This type of machine tool is customdesigned for specific operation requirements and, therefore, its resources are minimized and, in turn, the machine cost is low and its performance is robust. The drawback of DMTs is that they cannot be costeffectively converted when parts change. To address this challenge, flexible CNC machine tools have been developed and adopted in many industries. By contrast to DMTs that are designed around a specific part and therefore are inexpensive, CNCs are designed before the operation requirements are known and, thus, they often have wasted resources that make customers pay for features they do not need. Further, these machines may not be able to handle the new operation demands (e.g., spindle power, geometric accuracy). The challenge, therefore, is to adopt the DMT approach and design a machine around a part family or a set of parts (rather than a specific part, so conversion by rapid reconfiguration of the machine is possible) and use CNC technology to drive the machine. This hybrid machine (i.e., the RMT),therefore, has a customized flexibility that makes it less expensive than generalpurpose CNCs 6. These novel machine tools are discussed in detail throughout this paper. One characteristic of RMTs is modularity: both in the mechanical structure and in the controller. Modular machine tools (MMTs) are being produced in industry with varying degrees of modularity. At the machine level, several companies (e.g., Lamb, Cellular Concepts, Heller, and Mazak) add and delete standard units (e.g., three perpendicular axes of motion with one cutting tool) to a line as needed. Special modular units have been developed expressly for the Russian automotive industry 7. The concept of modular units for manufacturing equipment is also briefly discussed in the context of concurrent product and production system design 8. Garro and Martin 9 provided an overview of the modular design of a machine tool including interactions with the environment (e.g., operators and other machines) and the determination of control modules. Zatarain et al. 10 developed a method to analyze the dynamic stiffness of a machine tool using precalculated component information. The notion of reconfiguration, however, extends beyond a customized-assembly of modular elements. That is, reconfigurable systems are: (i) modular in their construction and therefore can be reconfigured by swapping modules as needed, (ii) convertible: individual modules can be repositioned or re-oriented without changing the topological characteristics of the machine. This level of reconfigurability is helpful in making quick, on-line changes to accommodate certain changes in the product family. Thus, reconfigurable machine tools can be designed to provide different levels of reconfigurablity and the design process starts with a thorough understanding of peculiarities (geometry, processes, tolerances, cycle time, reconfiguration time) of a given family of products to be machined. Since the machine is designed around a part family, the reconfigurable machine offers customized flexibility at lower cost; that is the right kind of flexibility without any wasted-flexibility. Three methodologies are discussed in a subsequent section. A systematic methodology for the kinematic synthesis of RMTs starting from a mathematical description of the machining tasks 11, a methodology to evaluate the dynamic stiffness of RMTs 12, and one that evaluates machine dynamic errors using module information 13. In this paper are also provided three example operation scenarios, each with different types of operation requirements, to illustrate the characteristics of RMTs and the differences between RMTs and other types of machine tools (i.e., dedicated, CNC, and modular). 2 MANUFACTURING REQUIREMENTS The dominant production requirements for large machining systems are (1) mix (i.e., set of parts to be produced), and (2) volume (amount produced per unit time of each part) as well as changes in the part set and volumes over the lifetime of the machining system. A variety of factors will influence the change in part sets and volumes over time including tightening government regulations, increasing (decreasing) customer demands, etc. These factors may result in slight design modifications in the parts being produced, the introduction of new parts, the phasingout of current parts, or the increase (decrease) in the volume of each part. Similarly, the operation requirements for a machine tool consist of (1) the set of features that are produced and (2) the cycle time (i.e., time to complete the operation for one part) of each operation as well as changes in the feature sets and cycle times. Changes in the production requirements directly effect the operation requirements. A feature set may be altered (e.g., tolerance increased, hole enlarged), added or subtracted, or the required cycle time may be increased or decreased. The relationship between the production and operation requirements and the various types of machining systems and machine tools is shown in Table 1 and elaborated below. Table 1: A comparison of three systems. Dedicated machining systems (DMSs) are designed fornarrowly defined production requirements (typically onepart at a fixed volume) that are assumed to remainconstant over the lifetime of the machining system. Thesesystems are comprised of dedicated machine tools(DMTs), each of which is customdesigned to machine aspecific set of features (often a single feature) at aconstant cycle time. Therefore, while DMSs are tailored to their productionrequirements and, thus, are robust andinexpensive, they cannot costeffectively accommodatechanges in production requirements. Similarly, DMTs aretailored to specific operation requirements and, in general,cannot costeffectively accommodate changes in theoperation requirements. If the volume sharply increases,the DMS may not be able to accommodate the increaseand another system will need to be built or the saleopportunity will be lost. A slight design change to the part may trigger the need to modify one or more DMTs. Asthese machine tools are not designed such that they maybe costeffectively converted, the redesign and rampup of a modified (or entirely new) DMT will often be too costly.Further, the introduction of an entirely new part will requir the design of an entirely new machining system. Flexible manufacturing systems (FMSs) are designed for loosely defined production requirements that are assumed to significantly change in an unknown manner over time. Since the production requirements are not well defined, FMSs often contain excessive capability, and the customer pays for unneeded capabilities. Generalpurpose Computer Numerical Control (CNC) machine tools are the building blocks of FMSs. Loosely defined production requirements at the system level translate into loosely defined operation requirements at the machine level. As a result, CNCs often contain excessive functionality (e.g., a fiveaxis CNC may use only two axes in a given operation, or only 6 tools of a 24tool magazine may be utilized). Further, since CNCs are typically not designed for a specific set of operations, extensive testing must be performed to ensure the quality requirements will be met in the entire machine envelope. Increases in volume typically require additional CNCs.Reconfigurable Machining Systems (RMSs), which are designed for a specific range of production requirements, costeffectively combine the most attractive features of DMSs and FMSs: robust performance and the ability to accommodate new production requirements 14. Reconfigurable Machining Systems contain a combination of DMTs and CNCs, and incorporate, where appropriate, RMTs that are designed to produce specific sets of features for specific ranges of cycle times. Some operation requirements will be constant over the lifetime of the machining system and, thus, DMTs will be the appropriate choice for these operation requirements. Some operation requirements will change dramatically in an unknown manner over the lifetime of the machining system and, thus, CNCs will be the appropriate choice for these operation requirements. Since RMTs are designed for specific sets of features and ranges of cycle times, RMTs are tailored to the initial operation requirements and, when operation requirements change, RMTs may be costeffectively converted such that they are customized for the new requirements. 3 RMT CONTROL REQUIREMENTS The control components (hardware and software) of DMTs are customized for the DMTs requirements and, thus, do not contain unnecessary complexity and are correspondingly robust. However, these components cannot be costeffectively upgraded. Typical CNC controllers posses comprehensive architectures to provide processing flexibility; however, not all of the builtin functionality may be used. Thus, unnecessary costs are incurred due to software development, installation, and especially in maintenance and diagnostics. Further, similar to its mechanical components, CNC controllers posses control hardware resources (e.g., data acquisition boards, motor drives) that are often underutilized. For both DMTs and CNCs, the control components are not modular and, thus, are not scalable nor upgradable and new technology (e.g., advanced geometric compensation) cannot be costeffectively integrated. Controllers for RMTs must be based on the concept ofopenarchitecture 1517. In openarchitecture control,the software architecture is modular and, thus, hardwarecomponents (e.g., encoder) and software components(e.g., axis control logic) can be easily added or removed,and the controller can be costeffectively reconfigured.The RMT controller modularity allows the controller to becustomized to its current operation requirements and, thus,be robust and reliable, while maintaining the ability to bereconfigured when requirements change or newtechnology becomes available. Reconfiguration requirements introduce several new challenges for RMT controllers. The first challenge is the reconfiguration of the controller architecture that is required when the physical machine tool is reconfigured or new technology is integrated. Unlike DMT or CNC controller architectures, the RMT controller architecture is dynamic. For example, the addition of a linear axis to a oneaxis RMT may require the integration of an interpolator software module. Another challenge is the control of RMTs with multiple tools working independently (as in Figure 1) and RMTs with axes in nonorthogonal configurations (see the Second Example below). Strategies have been developed for the interpolation and control of RMTs with axes in nonorthogonal configurations. Another challenge is the integration of heterogeneous software and hardware components (e.g., fieldbus protocols, control signals, electrical contacts) that are developed by different vendors at different times. This will require standard software and electrical interfaces or the development of special components that interface custom devices to standard interfaces. To handle the challenge of costeffective reconfiguration of RMT controllers, work on a software tool known as a control configurator is being developed and is currently being applied to a prototype RMT (see the First Example). The controller (Figure 2) is composed of a configuration tool, a simulation tool, and a common HMI. The configuration tool is used to reconfigure the software whenever the prototype RMT structure is reconfigured (i.e., a linear axis is added or deleted). The tool allows the user to reconfigure the controller via a graphical user interface and generate the required software for the PCbased open architecture controller. The realtime simulation tool simulates the dynamics and discrete events of the electromechanical components and the machining process. This simulation is connected to the actual machine tool controller; thus, the user is able to evaluate and debug the controller without operating the real machine whenever the controller is reconfigured. Figure 2: Structure of prototype RMT controller. 4 RMT MECHANICAL REQUIREMENTS For a machine tool to meet the productivity and quality demands of an operation, it must fulfill a variety of requirements including the ability to produce the specified motions and satisfy the part tolerance specifications. To produce the required motions, the machine tools kinematic capabilities must be examined. To meet the part tolerance requirements, the mechanical sources of error (e.g., component geometric error, assembly errors, thermal deformation) must be examined. The following discusses two CAD/CAM tools that have been developed for RMT mechanical design. Kinematic Viability. One requirement in the design of a machine tool is kinematic viability (i.e., the machine tool must be able to perform the motions required to produce the feature set). For a DMT, the minimum required degrees of freedom (DOF) is designed given the feature set to be machined. The kinematic configuration, therefore, is limited. For a CNC, the entire machine tool, (typically 35 axes), is designed before the required set of operations is known. Therefore, CNCs typically have the required DOF for any operation; however, for many operations, the CNC possesses extra DOF creating wasted resources and unnecessary complexity. Similar to a DMT, the DOF of an RMT is designed after the operation set has been determined; however, the change in operation requirements, in addition to the initial operation set, must also be considered. As the operation requirements change, the DOF requirements may also change and, thus, the RMT will need to be mechanically modular to adapt to these changes. However, RMTs will not be generalpurpose modular machine tools; instead, they will be designed with the minimal amount of required modularity. This amount will be dictated by the range of operations that are required of the machine tool and the frequency of the change in these operations. A methodology (Figure 3) has been developed to determine the RMT kinematic requirements automatically 11. The machining operation is transformed into a task matrix (i.e., a homogeneous transformation matrix HTM) that contains the necessary motion requirements for the machine tool. The functional requirements of the machining operation are used to generate graph representations of candidate machine tools. A graph gives the overall topology of the machine tool and structural and kinematic functions are assigned to various portions of the graph. A library of machine tool modules (e.g., spindles, slides) containing structural and kinematic information for each module via HTMs, as well as connectivity information, is examined. Modules are assigned to various portions of the graph. The product of their HTMs is compared to the task matrix. If these matrices are equal, then the machine tool is kinematically viable. In this manner, all possible configurations can be determined. The viable configurations will be further reduced by other criteria (e.g., DOF, static and dynamic stiffness, thermal growth characteristics). This methodology also determines which modules must be added or deleted for each part in the part family. A CAD/CAM machine tool design package called PREMADE has been developed to assist the machine tool designer in implementing these algorithms. Figure 3: RMT kinematic design methodology. Structural Stiffness. One of the most critical design criteria for machine tools is structural stiffness. Static deflections cause geometric errors, and chatter may result if the dynamic structural characteristics are not properly designed. Based upon the designers experience, DMTs are designed to have the required stiffness characteristics for a specific operation. Conversely, CNCs are designed before the operation requirements are known; thus, extensive testing must be performed to ensure excessive deflections and chatter will not occur when a new operation is introduced. Similar to DMTs, RMTs are designed such that the structural stiffness requirements are ensured; however, RMTs have additional requirements. First, structural stiffness must be guaranteed for all configurations the RMT may take, and for all operations that may be performed. Also, RMT joints, in general, will be designed such that mechanical modules may be costeffectively rearranged and; thus, the joints cannot be treated as rigid (i.e., their compliance and damping are significant). Therefore, joint stiffness will dramatically affect the overall machine tool structural stiffness and must be carefully taken into account during the analysis stage. A systematic methodology is being developed to evaluate the structural stiffness of RMTs 12. The critical process parameters (e.g., cutting force magnitude and frequency content) are identified for the range of possible operations. For each design candidate, the joint parameters are determined assuming the joint model, or its describing function, is available. A substructuring method called nonlinear receptance coupling is used and the structural stiffness of each candidate is determined. The candidates are then evaluated using criteria such as static stiffness, fundamental frequency, minimum and mean dynamic stiffness within the frequency of interest, and coefficient of merit which evaluates performance with respect to chatter. An alternative to structural stiffness design is the use of vibration isolation systems (active, passive, or hybrid). Various vibration isolation strategies for RMTs were proposed by Yigit and Ulsoy 18. Nevertheless, careful structural stiffness design coupled with vibration isolation, where needed, will generally be preferred. Geometric Accuracy. Another machine tool design criterion is geometric accuracy. Machine tool geometricerrors create part geometry errors and, thus, dramatically affect part quality. Sources of machine tool geometric errors include tolerance errors in subcomponents, motion errors, static deflections due to weight and machining forces, thermal deformations, spindle runout, and assembly errors. A DMT is designed, based on the designers experience, so the machine tool geometric errors are such that the part tolerance specifications will be met. Given the complex nature of machine tool geometric errors, extensive testing is often required to ensure part tolerance requirements are met for high precision applications. For a CNC, the geometric errors are minimized given the cost constraint for the machine tool. Since the CNC is designed before the part is selected, extensive testing is often required to ensure part tolerance requirements are met. Similar to a DMT, the RMT mechanical structure is designed such that the machine tools geometric errors will not compromise part quality; however, two additional considerations must be taken into account. First, since RMTs are designed for a range of operation requirements, the most limiting part tolerance requirements will dictate the geometric error requirements of the machine tool. Second, the structure of an RMT may need to be reconfigured; therefore, for some applications, RMTs will require mechanical adapters that allow for the quick and accurate addition or deletion of mechanical modules. An overview of the repeatability properties of a variety of viable adapters is given in 19. A systematic methodology is being developed to analyze the accuracy of RMTs 13. An overview of the methodology is shown in Figure 4. Each module will have geometric, and possibly motion, related errors. The errors of existing modules may be represented deterministically if measurements have been performed. Otherwise, the errors are represented in a statistical manner. Assembly errors are also represented statistically. The geometric errors of each machine tool component and the assembly errors are mathematically described by HTMs, similar to the kinematic representation. Monte Carlo simulations are used to analyze the distribution of the tool position errors given the statistical distribution of component and assembly errors. The data is post processed and criteria (e.g., reliability, robustness) are being developed to systematically compare various machine tools. This methodology will be extended to the analysis of static errors resulting from machining forces and thermal deformation, and analysis modules will be written to integrate with the PREMADE software. Figure 4: RMT error evaluation methodology. 5 FIRST EXAMPLE PART CHANGE Examples of machine tool reconfiguration are presented in the following three sections. The first example considers the design of an RMT for the drilling process of precision cam tower holes. The part family consists of two automotive cylinder heads: a V8 single overhead cam and a V6 duel overhead cam (Figure 5). A machining line is to be designed to initially produce V8 heads. However, the line must have the capability to produce V6 heads when market demands changes; however, the line will produce only one head at any given time. As seen in Figure 5, each cam cap is located on its respective cam tower via two dowel pins; therefore, the cam tower holes which hold the dowel pins must be machined to tight tolerances. The V8 head has two cam caps and requires four precision holes that are colinear. The V6 head, however, has eight cam caps and sixteen precision holes that are not colinear. A machine tool will require at least two axes of motion (one to locate and one to feed) to produce the V8 head and at least three axes of motion (two to locate and one to feed) to produce the V6 head. Figure 5: Part family two automotive cylinder heads: V8 (left) and V6 (right). A large number of RMTs can be realized for these operation requirements; indeed, the PREMADE software discussed above determined scores of solutions given a modest module library. In this section a prototype RMT that was designed for these operation requirements 6 will be described. The prototype RMT is shown in Figure 6. For the V8 head, the twoaxis configuration of the RMT is employed: the horizontal linear axis positions the selffeeding spindle. To machine the V6 head, the threeaxis configuration is employed. The prototype RMT is designed such that it may be easily converted between the two and threeaxis configurations. This is accomplished by means of a standard interface on the saddle of both linear axes. This interface uses Ball Locks that allow mechanical components to be joined quickly (a screw turn locks the balls into the receiver bushing) and accurately (the primary Ball Locks and their associated bushings are precision machined). The spindle may be joined to the saddle of either axis and the vertical axis may be joined to the horizontal axis as well. When the prototype RMT is reconfigured mechanically, the controller must be modified. This cannot be accomplished using a PLC or a CNC controller; therefore, an open controller was utilized (Figure 2). This controller was modified such that one axis controller may be turned off or on via a screen command. The modular structure of the prototype RMT (in both hardware and software) allows it to be converted in a costeffective manner when the requirements change and provide a customized solution for both operations. Figure 6: Prototype RMT: twoaxis (left) and threeaxis (right) 6. 6 SECOND EXAMPLE FEATURE CHANGE The part family and production requirements in the second example are the same as in the first example (Figure 5). However, this example considers the design of an RMT for finish milling of the cylinder head inclined surfaces. The tooling, tolerances, process parameters, etc. are the same for both inclined surfaces; however, the surfaces of the V6 and V8 cylinder heads have different angles with respect to horizontal: 30and 45, respectively. If the cylinder heads were being produced on a DMS, a DMT would be customdesigned with one axis for the V8 cylinder head that is 30from horizontal. This would be the most economical solution if the V6 was never introduced. However, a new customdesigned DMT with one axis at a 45 angle would need to be built and tested for the V6 inclined surface finish milling operation if the V6 was introduced at a later date. In an FMS, a CNC station would require four or five axes (depending on the fixture and process plan) whereas only 3 motions are needed thus, there would be one or two wasted axes of motion. However, the introduction of the V6 cylinder head would just require a change in the part program. In an RMS environment, an RMT would be used where the spindle unit could be placed on the machine tool structure in two different locations such that the spindle unit was at either a 30 or a 45angle with respect to the horizontal. A new type of RMT, called the ArchType RMT (ATRMT) is being developed 20 for these types of operations. As seen in Figure 7, the ATRMT has two predetermined spindle unit locations. It is a nonorthogonal 3axis machine designed around parts with inclined surfaces. The spindle angle and position could be adjusted before the operation either by using an actuator on the arch axis or manually. Figure 7: ATRMT (left) and Parallel RMT (right). 7 THIRD EXAMPLE CYCLE TIME CHANGE The part family for the third example is a simple prismatic part and the operation that is considered is drilling an identical pattern of holes on two sides opposite of one another. Initially, the cycle time is such that a single spindle may be used: one side is machined, the part is indexed 180, and the second side is machined. Further, it is assumed that the final product is produced in a system containing several stations and that this particular operation has the longest cycle time. In this example, the affect of increased product demand and, hence, decreased cycle time, is explored. Since the operation that is considered is the bottleneck operation, if a DMS was utilized, the only way to increase the capacity of the system would be to build another line. If the increase in product demand were less than double, this would result in an underutilized system. Further, if demand returned to normal in the future, an entire machining line would remain idle. If an FMS was utilized, and additional station would be required, which would increase the cost. In an RMS, each station would be designed such that it may be costeffectively reconfigured, if required, to meet the increase in demand. For the operation being considered, one solution is to add another spindle opposite to the first, remove the indexing table, and simultaneously machine both sides (see Figure 7). This solution is based on the methodology of using multiple independent spindles for RMTs 5. More than half of the cycle time will be saved with this solution since the part will no longer need to be indexed. 8 SUMMARY AND CONCLUSIONS This paper provided a detailed overview of a new paradigm for machine tools reconfigurable machine tools. The effect of production and operation requirements on the design of RMTs was explored. The mechanical and control requirements of RMTs were given and systematic design tools that have been recently developed were reviewed. Three examples, illustrating various changes in operation requirements, were provided and RMTs were compared to dedicated machine tools, modular machine tools, and flexible CNCs.Reconfigurable machine tools provide a viable solution for manufacturing situations where operation requirements change within prescribed bounds over the lifetime of the machine tool. Like DMTs, RMTs are customized to their current operation requirements and, thus, are robust; however, RMTs are also designed such that they may be costeffectively converted when operation requirements change. Further, unlike CNCs that can accommodate a wide variety of operation requirements, RMTs are designed for a specific range of operation requirements and, thus, do not have wasted resources and functionality. Reconfigurable machine tools are also capable of costeffectively incorporating new technology, thereby extending the use of the machine tool. To provide an economical solution, systematic design tools will be needed to quickly analyze a variety of RMTs that must perform over a range of operation requirements. Such tools will include kinematic synthesis, structural stiffness and error analyses, controller configuration, etc. The examples provided in this paper have also illustrated the dramatic effect that production and operation requirements have on the design of RMTs and on the different types of RMT conversions (e.g., adding an additional axis, reorienting an axis, integrating new control and diagnostic algorithms) that are needed. 9 ACKNOWLEDGMENTS The authors gratefully acknowledge the financial support of the Engineering Research Center for Reconfigurable Machining Systems (NSF Grant EEC9592125) at the University of Michigan and the valuable input from the Centers industrial sponsors. 10 REFERENCES 1 Sethi, A.K. and Sethi, S.P., 1990, Flexibility in Manufacturing: A Survey, International Journal of Flexible Manufacturing Systems, Vol. 2, pp. 289328. 2 Mehrabi, M.G. and Ulsoy, A.G., 1997, StateoftheArt in Reconfigurable Machining Systems, ERC/RMS Technical Report, University of Michigan, Ann Arbor, Michigan. 3 Koren, Y., Heisel, U., Jovane, F., Moriwaki, T., Pritschow, G., Ulsoy, G., and Van Brussel, H., 1999, Reconfigurable Manufacturing Systems, Annals of the CIRP, Vol. 48/2, pp. 527540. 4 Bollinger, J. et al., 1998, Visionary Manufacturing Challenges for 2020, National Research Council Report, National Academy Press, Washington, D.C. 5 Koren, Y. and Kota, S., 1999, Reconfigurable Machine Tools, U.S. Patent 5,943,750. 6 Landers, R.G., 2000, A New Paradigm in Machine Tools: Reconfigurable Machine Tools, JapanUSA Symposium on Flexible Automation, Ann Arbor, Michigan, July 2326. 7 Genin, V.B. and Kozlov, A.I., 1990, New Modules Offer Enhanced Flexibility for Automatic Lines, Soviet Engineering Research , Vol. 61, No. 2, pp. 1417. 8 Rogers, G.G. and Bottaci, L., 1997, Modular Production Systems: a New Manufacturing Paradigm, Journal of Intelligent Manufacturing , Vol. 8, pp. 147156. 9 Garro, O. and Martin, P., 1993, Towards New Architectures of Machine Tools, International Journal of Production Research , Vol. 31, No. 10, pp. 24032414. 10 Zatarain, M., Lejardi, E., and Egana, F., 1998, Modular Synthesis of Machine Tools, Annals of the CIRP, Vol. 47/1, pp. 333336. 11 Moon, YM. and Kota, S., 1999, A Methodology for Automated Design of Reconfigurable Machine Tools, Proceedings of the 32nd CIRP International Seminar on Manufacturing Systems, Leuven, Belgium, May, pp. 297303. 12 Yigit, A.S. and Ulsoy, A.G., 2001, Dynamic Stiffness Evaluation for Reconfigurable Machine Tools Including Weakly Nonlinear Joint Characteristics, Proc. 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(Eds.), 1998, Open Architecture Control Systems: Summary of Global Activity, ITIA Series, Vol. 2. 16 Pritschow, G., Daniel, C.H., Jurghans, G., Sperling, W., 1993, Open Systems Controllers A Challenge for the Future of the Machine Tool Industry, Annals of the CIRP, Vol. 42/1, pp. 449452. 17 Pritschow, G. et al ., 2001, Open Architecture Controller, Annals of the CIRP, Vol. 50/2. 18 Yigit, A.S. and Ulsoy, A.G., 2000, Design of Vibration Isolation Systems for Reconfigurable Precision Equipment, JapanUSA Symposium on Flexible Automation, Ann Arbor, MI, July 2326. 19 Li, H., Landers, R.G., and Kota, S., 2000, A Review of Feasible Joining Methods for Reconfigurable Machine Tool Components, JapanUSA Symposium on Flexible Automation, Ann Arbor, MI, July 2326. 20 Katz, R. and Chung, H., 2000, Design of an Experimental Reconfigurable Machine Tool, JapanUSA Symposium on Flexible Automation, Ann Arbor, MI, July 2326. CIRP Annals - Manufacturing Technology Volume 50, Issue 1, 2001, Pages 269274可重构机床R.G. Landers, B.K. Min, and Y. Koren University of Missouri Rolla, Department of Mechanical Engineering, Rolla, Missouri University of Michigan, Department of Mechanical Engineering, Ann Arbor, Michigan 摘 要 可重构制造系统(RMSS)特有的结构系统,可以改变其控制系统以迅速响应市场的变化，RMSS是可重构机床(RMT)的一个主要组成部分。通过对比众多的传统机床，RMTS被设计为在一个特定范围内当操作要求发生变化时可以有效的进行转换的一种通用机械。在这篇论文中对RMTS的开发研究进行了概述，并提供了三个RMTS机床与传统机床相比较的例子。关键词 机床 机床模块 转换1 介绍 在传统设计上,专用制造系统(DMSS)被设计为用来生产某一特定部分的系统，在经济产量很高时可以生产很长一段时间。相反,柔性制造系统(FMSS)被设计为了容纳生产大量的甚至没有专门制造系统的各种配件的制造系统，FMSS的概论请见1，在经济产量很低时可以生产大量的不同零件。传统DMSS在经济上不可能适应快速变化的市场需求使,可以搭配使用FMSS。然而，FMSS不具有较强的稳定性，而且DMSS在许多生产的同时浪费了大量的资源2。可重构制造系统(RMSS)结合了柔性制造系统的优点，在许多场合人们认为可以解决上述问题3。这些系统的设计要在一个特定的范围之内(如产品生产工艺要求的混合度和体积)。更进一步，RMSS的设计具有灵活性，可以为目前的生产要求量身定做，可以将经济产量转化成一套新的生产工艺的要求。因此，这些系统具有经济性和稳定性，因为它们是专门生产的要求定制的，它们使用少量的资源和灵活的设计使成本有效的降低。事实上,可重构制造被认定为2020年制造业最具竞争力的六大挑战之一4。 随着生产的变化要求加工系统进行改变，因此，每个个体的操作要求需要改变。可重构机床(RMTS)是RMSS的主要执行部件。这些机床是十分合算的,因为他们是在一个给定范围的操作要求而量身订做的，可以很经济的改变以满足新的要求。Koren是在RMT概念设计的基础上专利5。如图1所示。为零件的尺寸和特征的变化,主轴可以迁移到不同的位置执行同样的操作或更换另一个主轴执行不同的操作。锭子也可以添加或删除以实现优化。 图1 重构机床 在今天，大型的工业生产中专用机床十分的常见，这类型的机床是为特定的操作要求所制造的，因此,它使用的资源最小,机器成本最低和性能最稳定。它们的缺点是不能有效地更换零件。为解决这一问题，已经制定了一种灵活的涉及众多行业领域的数控机床。通过对比，因为这种设计是对于一个特定部分的专门设计，因此它们十分便宜的，而之前的许多通用操作系统设计都是对于全部要求的设计，,因此,他们浪费了许多的资源，顾客将为他们不会用到的部分付费，更进一步，这些设计的机器可能无法处理许多新的要求。 设计一台生产零件族或者一组的部分零件(而不是一个特定的零件,这样快速转化的重构机器是不可能的)的机器的挑战在于应使用什么样的方法实现。该机器(即RMT),设计十分灵活使它比通用数控系统的花费要少6。在本篇论文中对这些机床进行了详细的讨论。RMTS的特征之一是模块化无论对于机械结构还是操作系统。在工业生产中组合机床工具(MMTS)正是存在了不同程度的模块化。在这台机器的标准上一些公司根据生产产品的需要删除或增加了某些模块。俄罗斯的汽车工业已经制定了明确的模块机组7。在现行的产品和生产背景下对生产设备设计模块化的概念进行了简单的讨论8。 Garro和 Martin 提供了一个模块化的概述，机床的设计包括互动环境(例如,经营者和其他机器)和确定的控制模块9。Zatarain等人提出了一种方法分析机床动刚度的信息。而重构超出了模块化的概念10。可重构系统(1)根据需要可以交换模块重新配置,(2)可转换:单独模块也可被重新设计以改变机器的功能，对于一线产品的变化这一水平的可重构性有助于其迅速做出适应性变化。因此,当深入的理解给定的系列产品得特性后(几何特性、过程、公差、周期时间,重构时间)，可重构机床旨在为其提供了不同层次的可重构技术实现其设计。机器设计的一部分可以采用定制的可重构机器，成本较低，这是十分正确的。在后续的讨论区将有三种讨论，一是在加工任务中，从数学描述RMTS运动的合成11。二是RMTS动态刚度的评价12。三是机器错误使用模块的信息13。 本文提供了三例操作情景，每一个都是不同类型的操作情景。阐述了RMTS的特点。RMTs与其他机床之间的差异(例如,专用机床、CNC、模块化机床)。2 制造要求 加工系统生产要求主要有(1)组合(即,一套零件各部分的组合），（2）数量（一定时间内各部分生产的数量）。随着时间的推移多种因素将使部分设置的变化包括政府法规、客户的需求的增(减)等。这些因素可能导致设计进行轻微的修改，在零件的生产中要引进新的零件或修改零件的某些部分。同样的，机床加工操作的要求（1）设定生产所需要的功能，（2）周期时间（例如完成某一部分操作所需要的时间）。生产工艺要求的变化将