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1、Flexible ManufacturingAs an introduction to the subsequent discussions of production systems and advanced manufacturing technologies it is useful to present a definition of the term manufacturing system. A manufacturing system can be defined as a series of value-adding manufacturing processes conver
2、ting the raw materials into more useful forms and eventually finished products.In the modern manufacturing setting, flexibility is an important characteristic. It means that a manufacturing system is versatile and adaptable, while also capable of handling relatively high production runs. A flexible
3、manufacturing system is versatile in that it can produce a variety of parts. It is adaptable because it can be quickly modified to produce a completely different line of parts.A flexible manufacturing system is an individual machine or group of machines served by an automated materials handling syst
4、em that is computer controlled and has a tool handling capability. Because of its tool handling capability and computer control, such a system can be continually reconfigured to manufacture a wide variety of parts. This is why it is called a flexible manufacturing system.A FMS typically encompasses:
5、* Process equipment e.g. , machine tools, assembly stations, and robots* Material handling equipment e.g. , robots, conveyors, and AGVs (automated guided vehicles) * A communication system* A computer control system Flexible manufacturing represents a major step toward the goal of fully integrated m
6、anufacturing. It involves integration of automated production processes. In flexible manufacturin , the automated manufacturing machine and the automated materials handling system share instantaneous communication via a computer network. This is integration on a small scale. Flexible manufacturing t
7、akes a major step toward the goal of fully integrated manufacturing by integrating several automated manufacturing concepts: * Computer numerical control (CNC) of individual machine tools* Distributed numerical control (DNC) of manufacturing systems* Automated materials handling systems* Group techn
8、ology (families of parts)When these automated processes, machines, and concepts are brought together in one integrated system, an FMS is the result. Humans and computers play major roles in an FMS. The amount of human labor is much less than with a manually operated manufacturing system, of course.
9、However, humans still play a vital role in the operation of an FMS. Human tasks include the following: * Equipment troubleshooting, maintenance, and repair* Tool changing and setup * Loading and unloading the system* Data input* Changing of parts programs* Development of programsFlexible manufacturi
10、ng system equipment, like all manufacturing equipment, must be monitored for bugs, malfunctions, and breakdowns. When a problem is discovered, a human troubleshooter must identify its source and prescribe corrective measures. Humans also undertake the prescribed measures to repair the malfunctioning
11、 equipment. Even when all systems are properly functioning, periodic maintenance is necessary.Human operators also set up machines, change tools, and reconfigure systems as necessary. The tool handling capability of an FMS decreases, but does not eliminate involvement in tool changing and setup. The
12、 same is true of loading and unloading the FMS. Once raw material has been loaded onto the automated materials handling system, it is moved through the system in the prescribed manner. However, the original loading onto the materials handling system is still usually done by human operators, as is th
13、e unloading of finished products.Humans are also needed for interaction with the computer. Humans develop part programs that control the FMS via computers. They also change the programs as necessary when reconfiguring the FMS to produce another type of part or parts. Humans play less labor-intensive
14、 roles in an FMS, but the roles are still critical.Control at all levels in an FMS is provided by computers. Individual machine tools within an FMS are controlled by CNC. The overall system is controlled by DNC. The automated materials handling system is computer controlled, as are other functions i
15、ncluding data collection, system monitoring, tool control, and traffic control. Human/computer interaction is the key to the flexibility of an FMS.1 Historical Development of Flexible ManufacturingFlexible manufacturing was born in the mid-1960s when the British firm Molins, Ltd. Developed its Syste
16、m24. System 24 was a real FMS. However, it was doomed from the outset because automation, integration, and computer control technology had not yet been developed to the point where they could properly support the system. The first FMS was a development that was ahead of its time. As such, it was eve
17、ntually discarded as unworkable.Flexible manufacturing remained an academic concept through the remainder of the 1960s and 1970s. However, with the emergence of sophisticated computer control technology in the late 1970s and early 1980s, flexible manufacturing became a viable concept. The first majo
18、r users of flexible manufacturing in the United States were manufacturers of automobiles, trucks, and tractors.2 Rationale for Flexible Manufacturing In manufacturing there have always been tradeoffs between production rates and flexibility. At one end of the spectrum are transfer lines capable of h
19、igh production rates, but low flexibility. At the other end of the spectrum are independent CNC machines that offer maximum flexibility, but are capable only of low production rates. Flexible manufacturing falls in the middle of continuum. There has always been a need in manufacturing for a system t
20、hat could produce higher volume and production runs than could independent machines, while still maintaining flexibility.Transfer lines are capable of producing large volumes of parts at high production rates. The line takes a great deal of setup, but can turn out identical in a part can cause the e
21、ntire line to be shut down and reconfigured. This is a critical weakness because it means that transfer lines cannot produce different parts, even parts from within the same family, without costly and time-consuming shutdown and reconfiguration.Traditionally, CNC machines have been used to produce s
22、mall volumes of parts that differ slightly in design. Such machines are ideal for this purpose because they can be quickly reprogrammed to accommodate minor or even major design changes. However, as independent machines they cannot produce parts in large volumes or at high production rates.An FMS ca
23、n handle higher volumes and production rates than independent CNC machines. They cannot quite match such machines for flexibility, but they come close. What is particularly significant about the middle ground capabilities of flexible manufacturing is that most manufacturing situations require medium
24、 production rates to produce medium volumes with enough flexibility to quickly reconfigure to produce another part or product. Flexible manufacturing fills this long-standing void in manufacturing.Flexible manufacturing, with its ground capabilities, offers a number of advantages for manufacturers:*
25、 Flexibility within a family of parts* Random feeding of parts* Simultaneous production of different parts* Decreased setup time and lead time * More efficient machine usage * Decreased direct and indirect labor costs* Ability to handle different materials* Ability to continue some production if one
26、 machine breaks down 3 Flexible Manufacturing System ComponentsAn FMS has four major components:* Machine tools * Control system * Materials handling system *Human operators (1) Machine ToolsA flexible manufacturing system uses the same types of machine tools as any other manufacturing system, be it
27、 automated or manually operated. These include lathes, mills, drills, saws, and so on. The type of machine tools actually included in an FMS depends on the setting in which the machine will be used. Some FMS are designed to meet a specific, well-defined need. In these cases the machine tools include
28、d in the system will be only those necessary for the planned operations. Such a system would be known as a dedicated system.In a job-shop setting, or any other setting in which the actual application is not known ahead of time or must necessarily include a wide range of possibilities, machines capab
29、le of performing at least the standard manufacturing operations would be include. Such systems are known as general purpose systems. (2) Control SystemThe control system for an FMS serves a number of different control functions for system:* Storage and distribution of parts programs * Work flow cont
30、rol and monitoring * Production control *System/tool control/monitoringThe control area with the computer running the FMS control system is the center from which all activities in the FMS are controlled and monitored. The FMS control software is rather complicated and sophisticated since it has to c
31、arry out many different tasks simultaneously. Despite the considerable research that has been carried out in this area, there is no general answer to designing the functions and architecture of FMS software.The scheduler function involves planning how to produce the current volume of orders in the F
32、MS, considering the current status of machine tools, work-in-process, tooling, and so on. The scheduling can be done automatically or can be assisted by an operator. Most FMS control systems combine automatic and manual scheduling; the system generates an initial schedule that can be changed manuall
33、y by the operator. The dispatcher function involves carrying out the schedule and coordinating the activities on the shop floor, that is, deciding when and where to transport a pallet, when to start a process on a machining center, and so on.The monitor function is concerned with monitoring work pro
34、gress, machine status, alarm messages, and so on , and providing input to the scheduler and dispatcher as well as generating various production reports and alarm messages. A transport control module manages the transportation of parts and palettes within the system. Having an AGV system with multipl
35、e vehicles, the routing control logic can become rather sophisticated and become a critical part of the FMS control software. A load/unload module with a terminal at the loading area shows the operators which parts to introduce to the system and enables him or her to update the status of the control
36、 system when parts are ready for collection at the loading area. A storage control module keeps an account of which parts are stored in the AS/RS as well as their exact location. The tool management module keeps an account of all relevant tool data and the actual location of tools in the FMS. Tool m
37、anagement can be rather comprehensive since the number of tools normally exceeds the number of parts in the system, and furthermore, the module must control the preparation and flow of tools. The DNC function provides interfaces between the FMS control program and machine tools and devices on the sh
38、op floor. The DNC capabilities of the shop floor equipment are essential to a FMS; a “full” DNC communication protocol enabling remote control of the machines is required.The fact that most vendors of machine tools have developed proprietary communication protocols is complicating, the development a
39、nd integration of FMSs including multi-vendor equipment. Furthermore, the physical integration of multi-vendor equipment is difficult; for example, the differences in pallet load /unload mechanics complicate the use of machine tools from different vendors. Therefore, the only advisable approach for
40、implementing a FMS is to purchase a turn-key system from one of the main machine tool manufacturers. （3）Human OperatorsThe final component in an FMS is the human component. Although flexible manufacturing as a concept decreases the amount of human involvement in manufacturing, it does not eliminate
41、it completely. Further, the roles humans play in flexible manufacturing are critical. These include programming, operating, monitoring, controlling, and maintaining the system. 柔性制造 正如对制造系统和先进的制造技术后来的讨论，介绍制造业系统术语的定义是十分有用的。制造业系统的定义是一系列把原料转换成较有用的形式，最后完成产品的，能够使制造过程增值的系统。在现代制造业的框架中，柔性是一个重要的特性。这意味一个制造系统是
42、通用的和广泛适应的, 同时也有较高的生产能力。一个柔性的制造系统是通用的，它能生产多种零件。它具有适应性是因为它可以被很快地调整，生产完全不同的零件。一个柔性制造系统是一部单独的或成组的，有自动化材料处理系统服侍的，被计算机控制的，具有工具处理能力的机器。因为有工具处理能力和被计算机控制，这个系统可以被不断地调整，制造广泛和多样的零件。这是它为什么叫做柔性制造业系统的原因。一个FMS 典型地包括:*比如有处理仪器，机器工具,集会安置,和机械手*比如有材料处理设备，机械手，运送装置和 AGVs(自动化信息处理系统)*一个信息传输系统*一个计算机控制系统 柔性制造是制造业向完全整合的目标迈进的一个
43、重要的阶段。它包括自动化制造程序的整合。在柔性制造过程中，自动化的制造机构和自动化材料处理系统经由一个计算机网络被即时的沟通。这是在一个较小规模上的整合。 柔性制造对几个自动化制造概念的整合是实现完全整合的目标过程中所采取的一个重要的步骤：*计算机对机器设备分别的数字控制 (CNC)*制造系统的分布式数字控制 (DNC)*自动化材料处理系统*成组技术 (零件的系列)当这些自动化程序，机器和观念被引入一个整合的系统中的时候，FMS 就完成了。人和计算机在FMS中扮演重要的角色。人类的劳动量当然要比用手工操作的制造系统少。然而,人类仍然在FMS的操作中扮演着重要的角色。人类的工作包括下列各项: *
44、仪器故障修理，维护和修理*更换和调整工具*载入和卸载系统*数据输入*部分计划的变更*计划的发展柔性制造系统设备，像所有的制造业的设备一样，一定会出现出错，故障,和崩溃。当一个问题被发现的时候,修理它的人必须找出问题的来源，并提出纠正的方案。人也承担着采取正确的措施修理那发生故障设备的任务。即使当所有的系统正在正常地工作,周期的维护也是必需的。人类的操作员有必要完成安装机器，变换工具,重装系统的工作。FMS工具处理能力的减少不包括更换和调整工具，载入和卸载FMS。一但原材料被装入自动化的材料处理系统,它将被系统以规定的方式移动。然而，最初是由人类的操作员把原材料装入和把产品卸下材料处理系统的。人
45、也需要和计算机互动。人经由计算机控制FMS加工零件的程序。当FMS生产另外类型的零部件的时候，人必须改变它的程序。人在FMS中扮演劳动量很少但仍然是至关重要的角色。FMS的所有标准都是由计算机提供的。FMS中单独的加工工具都是由CNC控制的。而全面的系统是被DNC控制的。如同包括数据收集，系统监视，工具控制和信息交换控制等其他功能一样，自动化的材料处理系统也是由计算机控制的。人机交互作用是FMS柔性的关键。1.柔性制造的历史发展柔性制造在十九世纪六十年代中期出现在英国 Molins, Ltd公司。它发展System24。System24是真正的FMS。然而,因为自动化，整合和计算机控制技术仍未
46、发展到可以完全的支持系统的阶段，所以从刚一着手开始，它的命运就已被注定。第一个FMS超前于在它所在的时代。同样，它最后就像难以实现的东西一样被放弃。柔性制造在六十年代和七十年代剩下的时间一直停留在理论和概念阶段。然而，随着七十年代后期和八十年代早期，复杂的计算机控制技术的出现，柔性制造变成一项可行的概念。美国的柔性制造最早的使用者主要是汽车，卡车和拖拉机制造业。2.柔性制造的原理在制造业中总是存在生产率和柔性之间的矛盾。一方面是流水线能够实现高的生产率,但是柔性低。另一方面是独立的CNC机构能提供最大的柔性,但是生产率低。柔性制造则在二者之间。制造业一直以来就有一个需求，就是一个系统有较高的生
47、产率，独立性，同时有柔性。流水线以高的生产率能够产生大量的零件。流水线需要很多的设备,但是失去其中的一部分能引起整个的流水线的停工，而且需要重新配置。这是它最为关键的缺点，因为这意味着流水线在没有代价高昂的，长时间的关闭和重新装配的情况下，不能生产不同的，即便是同一系列的零件。 传统的CNC设备已经用来小批量地生产在设计中有些微小差别的零件。 这是一种很理想的设备，因为它们能被通过重新编程很快的适应较小的，甚至主要的设计变化, 然而作为独立的设备，它们不能以较高的生产率大批量的生产零件。FMS比独立的CNC设备拥的更高的产量和生产率。它们的柔性还不能够与独立的CNC设备相比，但是已经接近。柔性
48、制造关于中间基本能力的显著特点是，大多数的情况需要有足够的柔性被迅速的改造用来生产别的零件或产品的前提下，能以中间的生产率生产中间数量的产品。柔性制造填补了制造业中的空白。 柔性制造是由它的基本能力为制造者提供许多的利益:* 可以制造相似的零件* 随意更换零件* 同时生产不同的零件* 减少装备时间和交货期* 有效率的机器用法* 减少了直接的和间接的劳动费用* 处理不同材料的能力* 如果一部机器崩溃继续生产的能力3 柔性制造系统的组成FMS 有四个主要的组成部分: *机器工具 *控制系统 *原料搬运系统 *人类的操作 (1)机器工具柔性制造系统同任何其他的制造系统一样，使用相同类型的机器,是被自动控制或用手操作。这些包括车床，磨床，钻床，插床,等等。这些典型的机器实际上被FMS控制着，当系统需要哪个时就调用那个机器。一些FMS被设计成符合一种特性，能够定义明确的需要。在这样情况下机器工具在系统中将会只是调用那些必需的为了计划的操作。这样的系统成为被人们所关注的系统。 在一个工作环境设定中,或实际的应用中，应用之前不知道的任何设定或一定必然地包含宽范围的可能性,至少能够控制或操作机