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附錄A 英文文獻翻譯Reconfigurable manufacturing systems: Principles, design, and future trendsAbstract :Reconfigurable manufacturing systems (RMSs), which possess the advantages of both dedicated serial lines and flexible manufacturing systems, were introduced in the mid-1990s to address the challenges initiated by globalization. The principal goal of an RMS is to enhance the responsiveness of manufacturing systems to unforeseen changes in product demand. RMSs are cost-effective because they boost productivity, and increase the lifetime of the manufacturing system. Because of the many streams in which a product may be produced on an RMS, maintaining product precision in an RMS is a challenge. But the experience with RMS in the last 20 years indicates that product quality can be definitely maintained by inserting in-line inspection stations. In this paper, we formulate the design and operational principles for RMSs, and provide a state-of-the-art review of the design and operations methodologies of RMSs according to these principles. Finally, we propose future research directions, and deliberate on how recent intelligent manufacturing technologies may advance the design and operations of RMSs.Keywords: reconfigurable manufacturing systems, responsiveness, intelligent manufacturing1 IntroductionThe world of manufacturing has changed dramatically in the last 100 years in response to economic and social circumstances. Driven by different requirements in various periods, manufacturing technologies and new paradigms have been introduced to address economic challenges, and respond to social needs. Facing the requirement of cost-effectiveness, Henry Ford invented the moving assembly line in 1913, which began the mass production paradigm. In the 1970s, the Japanese manufacturing industry started formulating lean manufacturing principles, and since then consistent product quality has been a major focal point. In the late 1970s, the development of computer numerical control (CNC) machines facilitated the creation of flexible manufacturing systems (FMS), which enabled producing a variety of products on the same manufacturing system [1].Globalization that began in the 1990s transformed the competitive landscape. Manufacturing companies started facing unpredictable market changes, including rapidly varying product demand, and frequent introduction of new products. This made the design of manufacturing systems for new factories a major challenge, because it impacts the factory performance for many years after the factory design. It became essential that new factories should possess a new type of manufacturing system –– A system designed for rapid responsiveness to unforeseen market surges and unanticipated product changes.In response to this challenge, in 1995, Dr. Koren proposed designing factories with new system architecture that he called “reconfigurable manufacturing system.” The RMS has an open system architecture that enables adding machines to existing operational systems very quickly, in order to respond (1) rapidly, and (2) economically to unexpected surges in market demand [2]. Utilizing RMS enables building a “l(fā)ive” factory that its structure changes cost-effectively in response to markets and customers’ needs, so it can keep supplying products at competitive price for many years after the factory design.In 1996, Dr. Koren’s proposal to form an “engineering research center forreconfigurable manufacturing systems” (ERC-RMS) was approved by the U.S. National Science Foundation (NSF). The ERC-RMS was established at the University of Michigan with a grant of 33 million USD for 11 years from NSF. Matching funds of 14 million USD were granted by industry and the State of Michigan. The center created the RMS science base and invented RMS technologies that were implementedin the U.S. automotive and aerospace industries, enhancing thereby the industry competitiveness.It is worthwhile to note that the State of Michigan is home to notable inventions in manufacturing. In 1913, the first moving assembly line, invented by Henry Ford, was installed at the Ford Highland Park plant in Michigan. The second breakthrough invention was numerical control that was invented by John Parsons [3] in his company in Traverse City, Michigan. The recent innovation is the RMS. RMS is a new type of manufacturing system that can change its system structure and resources rapidly and cost-effectively, in order to possess “exactly the capacity and functionality needed, exactly when needed.” Figure 1 illustrates how the inventions from Michigan have transformed the landscape of manufacturing paradigms.The ERC-RMS has defined the key characteristics for RMS, and invented patents and software packages that have provided the basis for developing new reconfigura-tion technologies. The developed technologies have been successfully implemented in U.S. automotive companies ––Ford, General Motor, and Chrysler –– which have increased their system responsiveness [4] and created substantial economic value for these firms [5]. RMS is not only an open-architecture manufacturing system that can respond to the challenges of globalization [6], but also one that boosts productivity, enhancing thereby the competi-tiveness of manufacturing enterprises. RMS can also achieve agility and sustainable manufacturing [7,8].In this paper, we formulate the principles that guide the design and operations of RMS. According to these principles, we review and evaluate the state-of-the-art RMS design issues presented in the literatures. Possible future developments of RMS arediscussed as well.Fig. 1 Manufacturing inventions initiated in Michigan2 RMS characteristics and principlesThe three main goals of all manufacturing systems are cost, product quality, and responsiveness to markets. Respon-siveness is achieved by designing manufacturing systems for upgradable capacity and modifiable functionality. Comparing RMS with other types of manufacturing systems from the perspective of these goals, highlights the advantages of RMS.? RMS combines advantages of dedicated lines and flexible systemsIn the last decades of the 20th Century the manufacturing industry utilized two types of common manufacturing systems: Dedicated manufacturing lines (DMLs) and FMSs. DMLs are designed to enable mass production of a specific product at a very low cost and very high throughput. FMSs are designed to enable production of any product (confined within a geometric envelope), but compared with DMLs their throughput is very low.The DML is designed with fixed automation that produces the company’s core product at a very high rate. During the production, many tools can operate simultaneously on every machine in the line, leading to extremely high system throughput. The DML structure is fixed and cannot be changed neither to increase the throughput nor to produce a different product. If the market requires higher throughput, the DML cannot supply the full demand and the firm loses sale opportunities and consequently may lose market share. If the market requires a different product, the DML is useless and must be scrapped.By contrast, FMSs possess general flexibility that can produce a variety of products, but their production is by far more expensive than producing on DMLs. The FMS consists of general-purpose CNC machines and other forms of programmable automation. By contrast to a DML machine on which many tools operate simultaneously, each CNC machine uses a single tool during its operation. Therefore, the throughput of FMS is by far lower than that of DML (for the same investmentcost). The main drawbacks of FMS are the high investment cost (on both machines and tooling) and the relatively low throughput. Due to the high investment on CNC equipment, and the large number of cutting tools in the system, producing high volumes on FMS becomes a significant economic issue.The main advantage of RMS is that its functionality and capacity can be changed (1) rapidly and (2) cost-effectively. It is a feature that neither a DML nor an FMS possesses. The throughput of RMS is higher than the FMS throughput, but it is lower than that of a DML (for the same investment cost). The RMS is designed around producing a family of parts (e.g., cylinder heads, which are manufactured in reconfigurable machining systems) or products (e.g., engines, which are assembled in reconfigurable assembly systems), so its flexibility is by far higher than that of aDML. A thorough comparison of these three types of manufacturing systems is presented in Ref. [9], and their comparison with adjustable manufacturing systems is presented in Ref. [10].? Core characteristics and principles of RMSThe RMS is defined as follows: An RMS is designed at the outset for rapid change in structure, as well as in hardware and software components, in order to quickly adjust its production capacity and functionality within a part family in response to sudden changes in market or regulatory requirements.The RMS possesses six core characteristics that are summarized in Table 1. The six core RMS characteristics reduce the time and cost of reconfiguration,thereby enhancing system responsiveness. They are widely implemented today in the automotive, aerospace, food and beverage industries in the U.S. Based on these RMS core characteristics, the following RMS principles are formulated.RMS principles:? Design manufacturing system capacity for cost-effective adaptation to future market demand (scalability);? Design the manufacturing system for adaptation to customer’s new products (convertibility);? Design optimally embedded product quality inspection into manufacturing systems (diagnosability);? Design the manufacturing system around a product family (customization); 5)Maximize system productivity by reconfiguring operations and reallocating tasksto machines;6)Perform effective maintenance that jointly maximizes the machine reliability and the system throughput.The first four are system design principles that utilize the characteristics of “modularity” and “integrability” to enable cost-effective design. For example, at the system level, every machine is a module and the integration is done with material handling systems (e.g., a gantry or a conveyor). Principles 5 and 6 are system operational principles that improve the system productivity and reliability. Based on Principle 5, the ERC-RMS created system-balancing software that was implemented in 22 factories of General Motors and Chrysler and generated substantial savings. For example, Mr. Brian Harlow, VP Chrysler reported: “By using the ERCRMSline-balancing software, Chrysler succeeded in saving 10% of the operating costs on engine assembly lines in the Mack Avenue Engine Plant in Detroit, which is extremely significant.”Mathematical definitions have been proposed for the RMS key characteristics [11], especially for scalability [12], convertibility [13], and an integrated multiattribute reconfigurability index [14]. These characteristics and principles are applied to the design of different types of reconfigurable manufacturing systems, including machining systems, fixturing systems, assembly systems, and material handling systems [15,16], by using various models [17–20] and methodologies [21,22].? Examples of reconfiguration technologiesIn order to illustrate the RMS core characteristics, three examples of reconfiguration technologies –– machine, inspection, and system –– are presented below.1) Reconfigurable machine toolsReconfigurable machine tools (RMTs) are designed for a specific range of operational requirements, and can be rapidly converted from one configuration to another. The design of the RMT is usually focused on a specific part family, and should be rapidly adjustable to changes in its structure and/or operations to manufacture various parts of that part family. The world-first patent on RMT was issued in 1999 [23].Figure 2(a) shows an arch-type RMT that was built by the ERC-RMS and exhibited in 2002 at the International Manufacturing Show in Chicago. It was designed to drill and mill on inclined surfaces in such a way that the tool is perpendicular to the surface. This RMT is reconfigurable to five angular positions of the spindle axis ranging from–15° to 45° at steps of 15°, and the reconfiguration from one angle to another takes less than 2 min. It was utilized to mill and drill engine blocks at angles of 30° or 45°.2) Reconfigurable inspection machineThe reconfigurable inspection machine (RIM) represents a class of in-process inspection machines that can be reconfigured to fit the inspected part geometry. The world-first patent on RIM was issued in 2003 [24].Figure 2(b) shows an example of an RIM that is composed of a precision conveyor moving the part along one accurate axis of motion within an array of electro-optical devices, such as digital or line scanning cameras, and laser-based sensors. Depending on the part that is being measured, the location and number of sensors in the RIM canbe reconfigured to fit the geometry of the inspected part. The RIM depicted in Fig. 2(b) was configured to measure cylinder heads. On one side of the part there are two laser sensors; on the other side there are additional three laser sensors as well as an accurate computer-vision system.In 2006, General Motors installed an RIM that was developed by the ERC-RMS at its engine plant in Flint, Michigan. This RIM utilized machine vision to efficiently detect small surface pores ( < 1 mm) on engine blocks at the line speed to inspect each part. Utilizing the RIM has significantly improved the quality of the product and greatly reduced the number of recalls because of noisy engines.Fig. 2 Reconfiguration machine tool (RMT) and reconfigurable inspection machine (RIM) developed at the ERC-RMS. (a) RMT; (b)RIM3) Reconfigurable manufacturing systemA typical RMS integrates CNC machines and several RMTs that are utilized to manufacture a family of products, as well as product quality inspection machines that inspect the product during its manufacturing (i.e., not only at the end of the production line). The structure of an RMS is easily changeable to enable adding more production resources. The option of reconfiguration by adding production resources should be planned at all levels,hardware, software and controls, to enable adding machines, in-line inspection stations, gantries, etc. The world-first patent on RMS was filled in 1998 [25].The Ford Windsor Engine Plant that was designed and built in 1998–2000 contains about 120 CNC machines that are arranged in a reconfigurable system architecture that consists of 20 stages, with 6 machines per stage (as shown in Fig. 3) [26]. Ford Motor Co. called this system: “Flexible, reconfigurable manufacturing system.” Flexible because the CNC machines can produce multiple product variants.Fig. 3 Ford Winsor Engine Plant with CNC machines [26]Note that, at the system level, each CNC machine is a module, and its function can be converted when a new type of part is required to be manufactured by the system. At each stage of the system, there are multiple parallel CNC machines that are integrated into the system by using gantries to load and unload the CNCs. Furthermore, all the stages in the system are integrated into one large system by overhead gantries that transport parts between the stages. This system possesses the characteristic of diagnosability by including in-line inspection stations that are located next to critical machining stations. This system is scalable, namely, it is easy to add machines to the system to increase the system capacity. Actually, since 2000, the Ford plant went through three reconfigurations in which capacity was added. Note that, if the CNCs in some stages were replaced by RMTs that can process a certain part family, then the customization characteristic would be implemented.The RMS principles are widely used in the design of reconfigurable machines [27], machining systems [15], and assembly systems [16]. Next, we review the related research problems in system-level design and operations. Different from other general reviews [11,15,16,22], this paper reviews the design and operations of RMSs according to the principles that we have formulated in Section 2.2.3 Design and operations of reconfigurable manufacturing systemsThe designer of a manufacturing system has to determine:1)The system configuration –– the way that machines are arranged and interconnected in the system;2) the equipment –– the number and type of machines, the material handling system, and the in-line inspection equipment; 3) the process planning –– assigning operations to each machine in the system.3.2 Selecting the system configurationThe performance (e.g., throughput) and characteristics (e.g., scalability) of the manufacturing systems signifi-cantly depend on the system configuration [28]. We elaborate here on three types of manufacturing system configurations: Serial production lines, parallel systems, and reconfigurable manufacturing systems. The system type should be carefully determined at the system design stage because once determined, it cannot be changed in the future.Depending on the business goals of the manufacturing enterprise, four major performance metrics should be considered and prioritized when selecting the system configuration:3.2.1 Investment cost;3.2.2 Throughput resilience to machine failures;3.2.3 Speed of responsiveness to markets (i.e., increasing throughput to match future higher demand);3.2.4 Level of consistency in product quality in mass production environment.Traditional configurations of manufacturing systems are mainly of two types: Pure serial lines that consist of dedicated or flexible machines, and pure parallel systems that are composed of CNC machines. The drawbacks of serial machining lines are the high sensitivity of their throughput to machine failures, and the lack of respon-siveness to changing markets. The parallel configurations are not sensitive to machine failures, and can easily increase their throughput by adding more machines in parallel. However, parallel configurations are very expen-sive because: 1) Each machine must be capable of performing all the production tasks, which significantly increases the capability of each machine and consequently its cost, and 2) the total tooling cost in the system is expensive (the tool magazine of each machine must include all tools needed to produce the part). Because of these drawbacks, parallel systems are rarely found in practice.For large machining systems, there are two types of configurations that are commonly used in industry: 1) A configuration that consists of several serial lines40arranged in parallel (SLP), and 2) RMS configuration that consists of several stages, where each stage consists of multiple parallel identical machines (usually CNCs or reconfigur-able machines). The schematic layouts of the SLP and RMS configurations are shown in Fig. 4. Both systems in Fig. 4 have the same number of machines.The principal difference between SLP and RMS configurations is that RMS has crossover connections that enable operating the three machines in each stage in a parallel mode. In practice, a gantry that operates in each stage enables these connections. The gantry loads and unloads parts to or from each machine in that stage. The cost of these gantries makes the RMS more expensive than the SLP configuration. However, the two major advantages of RMS are: 1) Resources (e.g., machines) can be added very quickly and cost-effectively, enabling thereby high speed of response to changing markets; 2) if the gantries availability is higher than the machine availability, the throughput dependency on machine failures in RMS is smaller than that in serial lines.Freiheit et al. [29] developed a model that compares the throughput of SLPs and RMSs. It p