Showing papers in "Research in Engineering Design in 1998"
TL;DR: A general theory for system design is presented based on axiomatic design, which concisely represents the system design, the relationship among modules, and the control sequence in operating systems.
Abstract: A general theory for system design is presented based on axiomatic design. The theory is applicable to many different kinds of systems, including machines, large systems, software systems, organizations, and systems consisting of a combination of hardware and software. Systems are represented by means of a system architecture, which takes the form of the {FR}/{DP}/{PV}hierarchies, a ‘junction-module’ diagram, and the ‘flow diagram’. The ‘flow diagram’ for system architecture concisely represents the system design, the relationship among modules, and the control sequence in operating systems. The flow diagram of the system architecture can be used for many different tasks: design, construction, operation, modification, and maintenance of the system. It should also be useful for distributed design and operation of systems, diagnosis of system failures, and for archival documentation.
523 citations
TL;DR: In this article, a reverse engineering and redesign methodology is introduced to address the need for new methods to evolve their products, and the methodology has had a positive impact on results by using a systematic approach, both within design education and industrial applications.
Abstract: New products drive business. To remain compe- titive, industry is continually searching for new methods to evolve their products. To address this need, we introduce a new reverse engineering and redesign methodology. We start by formulating the customer needs, followed by reverse engineering, creating a functional model through teardowns. The functional model leads to specifications that match the customer needs. Depending upon required redesign scope, new features are possibly conceived, or not. Next, models of the specifications are developed and optimized. The new product form is then built and further optimized using designed experiments. An electric wok redesign provides an illustration. The methodology has had a positive impact on results by using a systematic approach, both within design education and industrial applications.
284 citations
TL;DR: Some hypotheses about the design process, derived from the literature, are objectively tested using results obtained from protocol analyses of various electronics designers engaged in conceptual design.
Abstract: Many theories about the process, of design have been derived from prescriptive or descriptive analysis. There have been few attempts to empirically test these theories. Protocol analysis facilitates detailed inspection of the design process allowing design task analysis across the temporal dimension. Some hypotheses about the design process, derived from the literature, are objectively tested using results obtained from protocol analyses of various electronics designers engaged in conceptual design. Support for the hypotheses is found.
156 citations
TL;DR: This work has studied two outstanding, expert designers, and is able to draw some parallels between their design strategies, noting that they both take a systemic view of the design situation, choose to frame their views of the problem in a challenging way, and draw upon first principles to guide both their overall concept and detailed design.
Abstract: Most studies of designer behavior are limited to studies of novice or average-ability designers. We have studied two outstanding, expert designers, and are able to draw some parallels between their design strategies. We note that they both take a systemic view of the design situation, choose to frame their view of the problem in a challenging way, and draw upon first principles to guide both their overall concept and detailed design. Studying expert designers should enable us to identify the seeds of ‘best practice’. This should be useful in design practice and in education, for guiding the development of better-than-average designers.
153 citations
TL;DR: In this paper, the authors propose a concept called the "Datum Flow Chain" (DFC) to capture the underlying logic of an assembly at an abstract level, including the designer's strategy for constraining the parts and locating them accurately with respect to each other.
Abstract: Current CAD systems are ‘part-centric’ and do not capture the underlying logic of an assembly at an abstract level. We need to make CAD systems ‘assembly-centric’. To be able to lay out, analyze, outsource, assemble and debug complex assemblies, we need ways to capture their fundamental structure in a top-down design process, including the designer's strategy for constraining the parts kinematically and locating them accurately with respect to each other. We describe a concept called the ‘Datum Flow Chain’ to capture this logic. Most assembly problems occur due to ineffective datum logic or the choice of assembly procedures that are not consistent with the datum logic, if any, that was used to design the parts. The DFC relates the datum logic explicitly to the product's key characteristics, assembly sequences, and choice of mating features, and provides the information needed for tolerance analyses. Two types of assemblies are addressed: Type-1, where the assembly process puts parts together at their pre-fabricated mating features, and Type-2, where the assembly process can incorporate in-process adjustments to redistribute variation. Two types of assembly joints are defined: mates that pass dimensional constraint from part to part, and contacts that merely provide support. The scope of DFC in assembly planning is presented using several examples. Analysis tools to evaluate different DFCs and select the ones of interest are also presented.
146 citations
TL;DR: In this paper, the authors present a method for evaluating the ease-of-disassembly of products using a spreadsheet-like chart and a catalog of task difficulty scores derived from work-measurement analyses of standard disassembly tasks.
Abstract: This paper presents a method for evaluating the ease-of-disassembly of products. Its primary use is in designing products for recycling, but it also facilitates consideration of servicing and maintenance, and making environmentally-related decisions. The method is developed and discussed in the context of relatively small products that can be disassembled by a seated person using hand-held tools. The evaluation procedure is centered around a spreadsheet-like chart and uses a catalog of task difficulty scores. The scores were derived from work-measurement analyses of standard disassembly tasks, and provide a means of identifying weaknesses in the design and comparing alternatives quantitatively. The structure of the evaluation chart and the derivation of difficulty scores are explained, followed by a demonstration of analyzing a computer central processing unit. The limitations of the method and future extensions are outlined.
86 citations
TL;DR: Experimental observations are made about design iteration in a group setting, and those observations are compared with the existing models of the iteration process, finding some correspondence with existing models is noted, although there are also significant differences.
Abstract: This paper uses a laboratory experimental setting to make observations about the iteration process in engineering design. Iteration is an important and ubiquitous feature of engineering design. Previous research has constructed prescriptive mathematical models of the iteration process in an attempt to aid the design manager. In this paper, experimental observations are made about design iteration in a group setting, and those observations are compared with the existing models of the iteration process. Some correspondence with existing models is noted, although there are also significant differences. These differences could be used to improve the mathematical models of the iteration process.
80 citations
TL;DR: In this paper, a systematic approach to attachment design is presented, based on relatively new methodologies and guidelines for arranging all attachment features on plastic parts comprising snap-fit assembly, and classification of features into categories of locking features, locating features and enhancements of these is used as the basis for discussion.
Abstract: Traditional integral snap-fit attachment design focuses almost exclusively on the individual locking features, such as cantilever hooks, bayonet-fingers, compressive hooks and others. The positioning and orientation of other significant features on parts, such as those that facilitate or enhance engagement and eliminate unwanted degrees of freedom left by locking features, i.e. locating features and enhancements, are not considered. This paper builds on relatively new methodologies and guidelines for arranging all attachment features on plastic parts comprising snap-fit assembly. Classification of features into categories of locking features, locating features and enhancements of these is used as the basis for discussion. A systematic approach to attachment design is presented.
43 citations
TL;DR: In this paper, an ethnographic study of a mechanical engineering design class is presented, based on participant observation of one student design team of three students as they designed, tested and built an engineered solution to a problem over a period of ten weeks.
Abstract: This article reports on an ethnographic study of a mechanical engineering design class. The findings are based on participant observation of one student design team of three students as they designed, tested and built an engineered solution to a problem over a period of ten weeks. The paper describes the curricular efforts to provide social and material affordances both for learning and doing design, and the failure of students on the observed team to take up those affordances. It offers explanations for failure within a framework of conflicting classroom views and pedagogic issues. It discusses the implications of the observed student behavior for design education in general, and mechanical engineering design, in particular.
36 citations
TL;DR: This paper describes an evolutionary algorithm that was developed for catalog design that is based on genetic algorithms, but uses an object-oriented coding scheme to represent a design, and introduces unique crossover and mutation operators.
Abstract: This paper describes an evolutionary algorithm that was developed for catalog design. This algorithm is based on genetic algorithms, but uses an object-oriented coding scheme to represent a design, and introduces unique crossover and mutation operators. To account for the dependence of system performance on both system configuration and component selection, the evolutionary algorithm allows for simultaneous alterations of configurations and components. This new approach allows the consideration of alternate configurations and allows the configurations to evolve to make the best use of the available components. Using this evolutionary algorithm, a piping system was designed in which cooling fluid was delivered to three machines on a manufacturing floor at specified pressures and flow rates. The algorithm was able to find good designs that satisfied the given design specifications.
34 citations
TL;DR: The scope of this investigation is limited to systems represented by bond graphs, but the domain is wide enough to include many interesting applications like pump systems and vibration isolation systems.
Abstract: This research uses Genetic Algorithms (GA) to suggest new dynamic systems based on topological remapping of system constituents. The bondgraph representation of the dynamic system behavior is evolved by the operators encapsulated in the genetic algorithms to meet the specified design criteria. The resultant evolved graph is assembled by designers with schemes to produce design variants. Behavioral transformation and structural transformation are adopted as strategies to generate design variants that extend beyond the scope of parametric design into innovative design. Behavioral transformation involves changes in the structure of the representation graphs, while maintaining the functions. Structural transformation involves changes in the components and the subsystems represented by the graph fragments. GAs are used to implement the operators of the transformation to search the problem-solution space because GAs are very robust search routines. Further, since the goal is to generate many solutions, genetic speciation is used to diverge the search so as to uncover other desirable solutions. The dynamic systems are modeled using bond graphs. Bond graphs provide a unified approach to the analysis, synthesis and evaluation of dynamic engineering systems. Though the scope of this investigation is limited to systems represented by bond graphs, the domain is wide enough to include many interesting applications like pump systems and vibration isolation systems.
TL;DR: A hierarchical classification scheme is presented that brings order to the design space, and the ability to reduce viable options for any assembly situation to a number that will permit true optimization is reduced.
Abstract: The diversity of integral attachment snap-fit feature types (e.g. cantilever hooks, bayonet-fingers, compressive hooks, annular snaps, and others), and their possible combinations, sizes and locations and orientations on parts to enable assembly has made it appear that design possibilities may be unbounded. Attempts at understanding, no less optimization, seemed intractable. This paper presents a hierarchical classification scheme that brings order to the design space, and uses that classification scheme to define boundaries and size of the design space for achieving attachment at a level above feature detailing. Classification is based on the essential geometry of parts being assembled. The result is surprising order and simplicity, and the ability to reduce viable options for any assembly situation to a number (e.g. 8–10) that will permit true optimization.
TL;DR: In this paper, a qualitative analysis of 50 unstructured interviews carried out with members of two commercial design organizations was conducted to identify effective practices towards transfer on the part of designers and design managers.
Abstract: The notion of transferring existing design solutions to new design problems is a basic one. Transfer provides a means of tackling increasing complexity, of limiting risks and costs, and of capitalizing on experience. In practice, in design organizations, it can be hard to judge the outcome of transfer because there can be several, often obscure benefits and drawbacks. This work is therefore an attempt to identify effective practices towards transfer on the part of designers and design managers. It is based on a qualitative analysis of 50 unstructured interviews carried out with members of two commercial design organizations. The practices were classified inductively in 15 main categories, of which the most heavily populated were associativity-improving, criteria-broadening, effort-reducing, environment-influencing, error-averting and motivation-addressing. The results have both a practical relevance (since most of the effective practices could be readily taught to novice designers) and a more theoretical relevance (showing what designers believe makes design transfer problematic).
TL;DR: The research demonstrates the viability of a reformulation methodology that combines symbolic program transformation with numerical experimentation, an important first step in a research program aimed at automating the entire strategy formulation process.
Abstract: Automatic design optimization is highly sensitive to problem formulation. The choice of objective function, constraints and design parameters can dramatically impact on the computational cost of optimization and the quality of the resulting design. The best formulation varies from one application to another. A design engineer will usually not know the best formulation in advance. To address this problem, we have developed a system that supports interactive formulation, testing and reformulation of design optimization strategies. Our system includes an executable, data-flow language for representing optimization strategies. The language allows an engineer to define multiple stages of optimization, each using different approximations of the objective and constraints or different abstractions of the design space. We have also developed a set of transformations that reformulate strategies represented in our language. The transformations can approximate objective and constraint functions, abstract or reparameterize search spaces, or divide an optimization process into multiple stages. The system is applicable in principle to any design problem that can be expressed in terms of constrained optimization; however, we expect the system to be most useful when the design artifact is governed by algebraic and ordinary differential equations. We have tested the system on problems of racing yacht design and jet engine nozzle design. We report experimental results demonstrating that our reformulation techniques can significantly improve the performance of automatic design optimization. Our research demonstrates the viability of a reformulation methodology that combines symbolic program transformation with numerical experimentation. It is an important first step in a research program aimed at automating the entire strategy formulation process.
TL;DR: In this paper, the authors explore the data-based opportunities for continuous improvement in the product development process emerging alongside the increasing utilization of networked Information Technology (IT) applications and present three different product process visualizations.
Abstract: Product development has until recently been considered pure art instead of being a controllable process. However, the current competitive environment has forced companies to take a closer look in the way new products are being developed. A key element in this assessment is the development of a set of metrics, which describe the whole product development process. This article explores the data-based opportunities for continuous improvement in the product development process emerging alongside the increasing utilization of networked Information Technology (IT) applications. Based on data from information systems in the case-study companies, three different product process visualizations are presented. Each visualization is discussed both from the viewpoint of its explanatory power as well as its limitations. The results of the case-studies clearly indicate that the computerization of the engineering and design processes is generating new ways of measuring, understanding and improving product development. The appropriate measures combined with open communication and a learning environment can be used to create a cycle of continually improving the product development process.
TL;DR: The approach consists of first identifying the different failure modes of the process and then defining producibility metrics corresponding to the likelihood of encountering each failure mode, which is used to represent the degree to which a part is easily manufactured.
Abstract: This paper presents an approach to evaluating producibility which is intended to enhance the ability of engineers to quickly design low-cost and high-quality parts. We divide all production processes into two categories: trajectory-dominated processes in which a generic tool is moved in a trajectory to form the part shape, and process-physics-dominated processes in which shaped tools are used to form similarly shaped parts. We focus on process-physics-dominated processes and on producibility problems that arise because of part shape. We argue that for these processes the currently popular approach of representing parts as collections of geometric features may be inappropriate for evaluating producibility. We propose an alternative approach and representation. Our approach consists of first identifying the different failure modes of the process and then defining producibility metrics corresponding to the likelihood of encountering each failure mode. This set of metrics is used to represent the degree to which a part is easily manufactured. Finally, we demonstrate this approach by developing a set of metrics for evaluating the producibility of aluminum extrusions. We use extrusions from the Boeing 777 to validate the metrics.