柔性制造外文文獻翻譯@中英文翻譯@外文翻譯

1 Flexible Manufacturing As 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 converting 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 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 system 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: * 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 manufacturing. 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 takes 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 technology (families of parts) When these automated processes, machines, and concepts are brought together in one 2 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. 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 programs Flexible manufacturing 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 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 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 the 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 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 including 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 Manufacturing Flexible manufacturing was born in the mid-1960s when the British firm Molins, Ltd. Developed its System24. System 24 was a real FMS. However, it was doomed from the outset because automation, integration, and computer control technology had not yet been 3 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 eventually 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 major 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 high 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 that 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 entire 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 small 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 can 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 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: 4 * 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 machine breaks down 3 Flexible Manufacturing System Components An FMS has four major components: * Machine tools * Control system * Materials handling system *Human operators (1) Machine Tools A flexible manufacturing system uses the same types of machine tools as any other manufacturing system, be it 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 included 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 capable of performing at least the standard manufacturing operations would be include. Such systems are known as general purpose systems. (2) Control System The control system for an FMS serves a number of different control functions for system: * Storage and distribution of parts programs * Work flow control and monitoring * Production control *System/tool control/monitoring The 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 5 rather complicated and sophisticated since it has to carry 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 FMS, 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 manually 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 progress, 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 multiple 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 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 management 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 shop 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 and 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 implementing a FMS is to purchase a turn-key system from one of the main machine tool manufacturers. 6 （ 3） Human Operators The 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 it completely. Further, the roles humans play in flexible manufacturing are critical. These include programming, operating, monitoring, controlling, and maintaining the system. 7 柔性制造 正如對制造系統(tǒng)和先進的制造技術后來的討論，介紹制造業(yè)系統(tǒng)術語的定義是十分有用的。制造業(yè)系統(tǒng)的定義是一系列把原料轉換成較有用的形式，最后完成產品的，能夠使制造過程增值的系統(tǒng)。 在現(xiàn)代制造業(yè)的框架中，柔性是一個重要的特性。這意味一個制造系統(tǒng)是通用的和廣泛適應的 , 同時也有較高的生產能力。一個柔性的制造系統(tǒng)是通用的，它能生產多種零件。它具有適應性是因為它可以被很快地調整， 生產完全不同的零件。 一個柔性制造系統(tǒng)是一部單獨的或成組的，有自動化材料處理系統(tǒng)服侍的，被計算機控制的，具有工具處理能力的機器。因為有工具處理能力和被計算機控制，這個系統(tǒng)可以被不斷地調整，制造廣泛和多樣的零件。這是它為什么叫做柔性制造業(yè)系統(tǒng)的原因。 一個 FMS 典型地包括 : *比如有處理儀器，機器工具 ,集會安置 ,和機械手 *比如有材料處理設備，機械手，運送裝置和 AGVs(自動化信息處理系統(tǒng) ) *一個信息傳輸系統(tǒng) *一個計算機控制系統(tǒng) 柔性制造是制造業(yè)向完全整合的目標邁進的一個重要的階段。它包括自動 化制造程序的整合。在柔性制造過程中，自動化的制造機構和自動化材料處理系統(tǒng)經(jīng)由一個計算機網(wǎng)絡被即時的溝通。這是在一個較小規(guī)模上的整合。 柔性制造對幾個自動化制造概念的整合是實現(xiàn)完全整合的目標過程中所采取的一個重要的步驟： *計算機對機器設備分別的數(shù)字控制 (CNC) *制造系統(tǒng)的分布式數(shù)字控制 (DNC) *自動化材料處理系統(tǒng) *成組技術 (零件的系列 ) 當這些自動化程序，機器和觀念被引入一個整合的系統(tǒng)中的時候， FMS 就完成了。人和計算機在 FMS中扮演重要的角色。人類的勞動量當然要比用手工操作的制造系統(tǒng)少 。然而 ,人類仍然在 FMS的操作中扮演著重要的角色。人類的工作包括下列各項 : *儀器故障修理，維護和修理 *更換和調整工具 *載入和卸載系統(tǒng) *數(shù)據(jù)輸入 *部分計劃的變更 8 *計劃的發(fā)展 柔性制造系統(tǒng)設備，像所有的制造業(yè)的設備一樣，一定會出現(xiàn)出錯，故障 ,和崩潰。當一個問題被發(fā)現(xiàn)的時候 ,修理它的人必須找出問題的來源，并提出糾正的方案。人也承擔著采取正確的措施修理那發(fā)生故障設備的任務。即使當所有的系統(tǒng)正在正常地工作 ,周期的維護也是必需的。 人類的操作員有必要完成安裝機器，變換工具 ,重裝系統(tǒng)的工作。 FMS工具處理能力的減少不包括更換和調整工具，載入和卸載 FMS。一但原材料被裝入自動化的材料處理系統(tǒng) ,它將被系統(tǒng)以規(guī)定的方式移動。然而，最初是由人類的操作員把原材料裝入和把產品卸下材料處理系統(tǒng)的。 人也需要和計算機互動。人經(jīng)由計算機控制 FMS加工零件的程序。當 FMS生產另外類型的零部件的時候，人必須改變它的程序。人在 FMS中扮演勞動量很少但仍然是至關重要的角色。 FMS的所有標準都是由計算機提供的。 FMS中單獨的加工工具都是由 CNC控制的。而全面的系統(tǒng)是被 DNC控制的。如同包括數(shù)據(jù)收集，系統(tǒng)監(jiān)視，工具控制和信息交 換控制等其他功能一樣，自動化的材料處理系統(tǒng)也是由計算機控制的。人機交互作用是FMS柔性的關鍵。 1.柔性制造的歷史發(fā)展 柔性制造在十九世紀六十年代中期出現(xiàn)在英國 Molins, Ltd公司。它發(fā)展System24。 System24是真正的 FMS。然而 ,因為自動化，整合和計算機控制技術仍未發(fā)展到可以完全的支持系統(tǒng)的階段，所以從剛一著手開始，它的命運就已被注定。第一個 FMS超前于在它所在的時代。同樣，它最后就像難以實現(xiàn)的東西一樣被放棄。 柔性制造在六十年代和七十年代剩下的時間一直停留在理論和概念階段。然而，隨著 七十年代后期和八十年代早期，復雜的計算機控制技術的出現(xiàn)，柔性制造變成一項可行的概念。美國的柔性制造最早的使用者主要是汽車，卡車和拖拉機制造業(yè)。 2.柔性制造的原理 在制造業(yè)中總是存在生產率和柔性之間的矛盾。一方面是流水線能夠實現(xiàn)高的生產率 ,但是柔性低。另一方面是獨立的 CNC機構能提供最大的柔性 ,但是生產率低。柔性制造則在二者之間。制造業(yè)一直以來就有一個需求，就是一個系統(tǒng)有較高的生產率，獨立性，同時有柔性。 流水線以高的生產率能夠產生大量的零件。流水線需要很多的設備 ,但是失去其中的一部分能引起整個的流水線的停 工，而且需要重新配置。這是它最為關鍵的缺點，因為這意味著流水線在沒有代價高昂的，長時間的關閉和重新裝配的情況下，不能生產不同的，即便是同一系列的零件。 傳統(tǒng)的 CNC設備已經(jīng)用來小批量地生產在設計中有些微小差別的零件。 這是一種很理想的設備，因為它們能被通過重新編程很快的適應較小的，甚至主要的設計變化 , 9 然而作為獨立的設備，它們不能以較高的生產率大批量的生產零件。 FMS比獨立的 CNC設備擁的更高的產量和生產率。它們的柔性還不能夠與獨立的CNC設備相比，但是已經(jīng)接近。柔性制造關于中間基本能力的顯著特點是，大 多數(shù)的情況需要有足夠的柔性被迅速的改造用來生產別的零件或產品的前提下，能以中間的生產率生產中間數(shù)量的產品。柔性制造填補了制