外文翻译模块化设计：产品设计的分解与整合.doc

英文原文:Design for Modularity: Product Design for Decomposition and IntegrationABSTRACTIn the last few years, corporation has engaged in studies to improve their design processes, ranging from marketing to support. Recent government, academic and industrial sector initiatives have sought advance technologies for developing and managing product development environment. Many companies have established a concurrent design process for their product development and have recognized a need for tools in evaluating the level of decomposition and integration, while analyzing the impact on the final design. This article will propose a three-phase methodology for design of products while considering modularity, assembly and manufacture. KEYWORDSModularity, Group technology, Optimization, Decomposition, Classification1. IntroductionModular design is a design technique that can be used to develop complex products using similar components . Components used in a modular product must have features that enable them to be coupled together to form a complex product. Modular design can be also viewed as the process of producing units that perform discrete functions, and then the units are connected together to provide a variety of functions. Modular design emphasizes the minimization of interactions between components, which will enable components to be designed and produced independently from each other. Each component, designed for modularity, is supposed to support one or more function. When components are structured together, to form a product, they will support a larger or general function. This shows the importance of analyzing the product function and decomposing it into sub-functions that can be satisfied by different functional modules. Modularity can be applied in the product design, design problems, production systems, or all three. It is preferable to use the modular design in all three types at the same time.Modular products refer to products that fulfill various overall functions through the combination of distinct building blocks or modules. In the sense that the overall function, performed by the product, can be divided into sub functions that can be implemented by different modules or components. An important aspect of modular products is the creation of a basic core unit to which different elements (modules) can be fitted, thus enabling a variety of versions of the same module to be produced. The core should have sufficient capacity to cope with all expected variations in performance and usage.Most design problems can be broken down into a set of easy to manage simpler sub-problems. Sometimes complex problems are reduced into easier sub-problems, where a small change in the solution of one sub-problem can lead to a change in other sub-problems solutions. This means that the decomposition has resulted in functionally dependent sub-problems. Modularity focuses on decomposing the overall problem into functionally independent sub-problems, in which interaction or interdependence between sub-problems is minimized. Thus, a change in the solution of one problem may lead to a minor modification in other problems, or it may have no effect on other sub-problems.Modularity in production systems aims at building production systems from standardized modular machines. The fact that a wide diversity of production requirements exists has led to the introduction of a variety of production machinery, and a lack of agreement on what the building blocks should be. This means that there are no standards for modular machinery. In order to build a modular production system, production machinery must be classified into functional groups from which a selection of a modular production system can be made to respond to different production requirements. Rogers classified production machinery into four basic groups of “primitive” production elements. These are process machine primitives, motion units, modular fixtures, and configurable control units. It is argued that if a selection is made from these four categories, it will be possible to build a diverse range of efficient, automated and integrated production system.2Overview of Product DevelopmentProduct development is a necessary and important part of the activities performed by a manufacturing firm. Due to changes in manufacturing technology, consumer preferences, and government regulations (to name a few influences), existing products will become less profitable over time. The sales volume of a typical product starts slowly, accelerates, becomes flat, and then steadily declines. Although there may be a few products that remain profitable for many years, firms continually develop new products that will generate more profits. Product development determines what the firm will manufacture and sell. That is, it attempts to design products that customers will buy and to design manufacturing processes that meet customer demand profitably. Poor decisions during product development lead to products that no one wants to buy and products that are expensive to manufacture in sufficient quantity.A product development process is the set of activities needed to bring a new product to market. A product development organization includes the engineers, managers, and other personnel who make process and product engineering decisions and perform these activities. (Note that, in this paper, the term new product covers the redesign of an existing product as well.)Because making good decisions requires expertise and an organization of people can be experts in only a few things, a manufacturing firm specializes in a certain class of products. It focuses its attention on the market for that class of products, the technologies available to produce that class, and the regulations relevant to that class.Like other parts of the business, a product development organization seeks to maximize the profit of the manufacturing firm subject to the relevant regulatory and ethical constraints and other conditions that the firms owners impose based on their values. A product development organization does this by regularly introducing new products that the firm can manufacture, market, and sell. Fundamentally, then, a product development organization transforms information about the world (e.g., technology, preferences, and regulations) into information about products and processes that will generate profits for the firm. It performs this transformation through decision-making (Herrmann and Schmidt, 2002). Because the design problem is highly complex, product development teams decompose the problem into a product development process, which provides the mechanisms for linking a series of design decisions that do not explicitly consider profit.The following nine steps are the primary activities that many product development processes accomplish (Schmidt et al., 2002):Step 1. Identify the customer needs.Step 2. Establish the product specification.Step 3. Define alternative concepts for a design that meets the specification.Step 4. Select the most suitable concept.Step 5. Design the subsystems and integrate them.Step 6. Build and test a prototype; modify the design as required.Step 7. Design and build the tooling for production.Step 8. Produce and distribute the product.Step 9. Track the product during its life cycle to determine its strengths and weaknesses.This list (or any other description that uses a different number of steps) is an extremely simple depiction that not only conveys the scope of the process but also highlights the inherent (but unquestioned) decomposition. There are many other ways to represent product development processes and the component tasks, including the use of schedules or a design structure matrix (Smith and Eppinger, 2001).Manufacturing firms understand that design decisions (though made early in the product life cycle) have an excessive impact on the profitability of a product over its entire life cycle. Consequently, product development organizations have created and used concurrent engineering practices for many years (Smith, 1997, provides a historical view). Many types of tools and methods (such as cross-functional product development teams and design for manufacturing guidelines) have been created, adopted, and implemented to improve decision-making. Cooper (1994) identifies three generations of formal approaches to product development, all of which involve decomposition.It should be noted, however, that decomposition is not the only way to describe product development. As an alternative to decomposing a system design problem into subproblems, Hazelrigg (1996) proposes creating and refining system design models to express how detailed design variables affect the overall system performance. This approach suggests that a product development process would end with using the model to find the optimal design. Hazelrigg (1998) encourages this type of optimization but does not discuss the process of generating the profit maximization model.3. A Methodology for Design for ModularityA three-phase methodology is proposed for the development of complex products using the modularity concept 1,2. The proposed methodology matches the criteria set by the design for functionality, assembly and manufacture. Some of the major benefits associated with this methodology include:· Increased design accuracy, efficiency, and the reuse of existing design for new programs.· Potential for integration of the developed methodology and technology into the engineering design activities.· Modular product design and the process of planning the production are integrated in one overall engineering process in which product features are mapped into their feasible process(es) in a one to one correspondence.In order to implement this concept successfully, the manner in which the modules are selected is critical. By establishing simple interfaces within the modules, the numbers of interactions are then reduced. The steps associated with this methodology include:Phase I - Decomposition Analysis: Design for Modularity and Classification1. Product and problem decomposition.2. Structural and modular decomposition.3. Associativity analysis between the components and specification.4. Application of group technology classification system.5. Construction of the associativity measure matrix.6. Optimum selection of modules.Phase II - Product Analysis: Design for Assembly and Functionality Analysis1. Identify the components that could be produced and assembled separately.2. Determine of the order of disassembly and assembly for each sub-component module.3. Establish the interfaces based on the analysis of the design features.4. Determine of the order, which the sub-assemblies are assembled to produce the final product.Phase III - Process Analysis: Design for Manufacture1. Family identification and template retrieval.2. Determination of the logical order of GT codes for the process of modules.3. Machine and process parameter calculation.4. Variant process planning.4. Decomposition Analysis: Design for Modularity and ClassificationPhase I of the methodology further specifications associated with this phase are illustrated as follows:4.1. Needs Analysis The design engineer is usually given an ill-defined problem. In many situations, the designer has to respond to the mere suggestion that there is a need for a product to perform a certain function. One of the main tasks is to find out precisely what are the needs and what do customers really want. An important step in the design is to describe the product fully in terms of functional needs and physical limitations. These functional needs and physical limitations will form the product specifications. Surveying prospective purchasers or customers could collect information required to identify customer needs. Conducting a marketing study that begins by establishing target markets and customers can do this. Then customers wants and needs could be obtained by using several methods such as interviews and questionnaires. Also, similar products (competitive products) are investigated to find possible improvement opportunities by focusing on weakness points and desired features by customers. Next, customer wants and needs are arranged into groups and prioritized according to their importance. Needs analysis usually results in a statement of recognized needs and the expected manner in which that need should be met. 4.2. Product Requirements AnalysisResults of the needs analysis step are used to identify the product requirements. The development group begins by preparing a list of functional objectives needed to meet the customers primary needs. Further analysis of customer needs reveals operational functional requirements that impose both functional and physical constraints on the design. Secondary customer requirements will be categorized as general functional requirements; they are ranked secondary because they will not affect the main function of the product. That is, a product may lack one or more general functional requirement and still be considered as a functional product that meets the intended function. General functional requirements should be weighted with respect to their importance.4.3. Product Concept AnalysisProduct/concept analysis is the decomposition of the product into its basic functional and physical elements. These elements must be capable of achieving the products functions. Functional elements are defined as the individual operations and transformations that contribute to the overall performance of the product. Physical elements are defined as the parts, components, and subassemblies that ultimately implement the products function. Product concept analysis consists of product physical decomposition and product functional decomposition. In product physical decomposition, the product is decomposed into its basic physical components which, when assembled together, will accomplish the product function. Physical decomposition should result in the identification of basic components that must be designed or selected to perform the product function. Product functional decomposition describes the products overall functions and identifies components functions. Also, the interfaces between functional components are identified. 4.4. Product/Concept IntegrationBasic components resulting from the decomposition process should be arranged in modules and integrated into a functional system. The manner by which components are arranged in modules will affect the product design. The resulting modules can be used to structure the development teams needed. System level specifications are the oneto- one relationship between components with respect to their functional and physical characteristics. Functional characteristics are a result of the operations and tra