A Framework for Sufficiency Estimation of Engineering Design Models

Engineering design models are aids that provide the designer with the ability to visualize the form and predict the nature and behavior of any product. In each stage of design, these models are used to predict the result of, or guide, design specifications, at a time when the design can still be changed with minimal negative impact. To ensure the downstream validity of these specifications or decisions, the designer must construct models that have sufficient accuracy and resolution. Determining the goodness of a model for a particular design decision or specification is a fundamental and pervasive question in engineering. Though fast to construct, and generally inexpensive, models based on estimation and approximation may not provide information of sufficient quality to make an accurate evaluation. In contrast, the crispness and depth of information gained from detailed computational analysis or experimental trials may come at too great an expense. Hence, a key aspect of model construction in design is deciding whether a model is appropriate for a particular design specification or evaluation considering accuracy and cost factors. This paper explores the application of utility theory to the model construction problem. We also discuss how estimated model accuracy affects the confidence of selecting a particular model. We present this research through application to a racecar sway bar.

An Investigation of Catalogued Product Development Information at a Major Consumer Products Company

A study of product development practices at a major consumer product manufacturer, referred to as Company X, was undertaken to compare its methods to an earlier effort in modeling the flow of information in product design, referred to as the Design Information Flow Model. The model considers the recognized need in industry for the seamless capture, storage, and retrieval of design information. The research at Company X focused on the front end of product design, that is, the conceptual phase. It was learned that design, as defined by the Information Flow Model, is well represented at the front end of the company’s design process. However, this validation effort succeeded in uncovering certain voids, particularly in later states of the model. It was also learned that product documentation quality and quantity at Company X vary from project to project, indicating an important aspect to consider in our efforts to enhance computer-aided product design is the user.

Evolving a Functional Basis for Engineering Design

All products and artifacts are designed for a purpose. There is some intended reason behind their existence: the product or artifact function. Functional modeling provides an abstract, yet direct, method for understanding and representing an overall product or artifact function. Function modeling also provides a strategy for problem decomposition, physical modeling, product architecting, concept generation, and team organization. A formal function representation is needed to support function modeling, and a standardized set function-related terminology is necessary to achieve repeatable and meaningful results from such a representation. We refer to this representation as a functional basis; in this paper, we seek to reconcile and integrate two independent research efforts into a significantly evolved functional basis. These efforts include research from the National Institute of Standards and Technology (NIST) and two U.S. universities, and their industrial partners. The overall approach for integrating the functional representations is developed, in addition to the final results. The integration process is discussed relative to differences, similarities, insights into the representations, and product validation. Based on the results, a more versatile and comprehensive design vocabulary is obtained. This vocabulary will greatly enhance and expand the frontiers of research in design repositories, product architecture, design synthesis, and general product modeling.

Designing a Requirement Driven Product Development Process

This paper presents a technique to obtain a Design Structure Matrix (DSM) from a Design Matrix (DM). This technique enables us to obtain the design information flow pattern at early stage of the design, and apply the DSM system analysis and management techniques at the time when the most important decisions about the system and the design are made. The validity of this method is proven using a case study on the design integration process of an electrostatic chuck used in semiconductor wafer processing. The algorithm underlying this technique is also proven logically and mathematically to be valid.

Determining Relationships Between Modularity and Cost in Product Retirement

Modular product design allows the designer to control the degree to which changes in requirements affect the product. By promoting interchangeability, modularity also gives designers more flexibility, with decreased cycle time, to meet changing requirements. Specific advantages associated with modular products include economies of scale, standardization of assemblies, minimization of assembly time, improved serviceability, and many more. Modular architecture is traditionally made up of functionally independent clusters of components. Past definitions of modularity have centered on a one-to-one correspondence between form and function. An expanded definition of product modularity has been used, which not only includes function, but also form and life-cycle process (manufacture, assembly, retirement, etc.) relationships. Modules contain a large number of components having very few similarities and dependencies on components not in the same module. This definition of product modularity differs from most, due to the inclusion of the similarity aspect. Modular products that are modular with respect to retirement are well designed for reuse, remanufacturing, recycling, and disposal. Apart from addressing the incorporation of product retirement into product modularity, a comparison of retirement costs and product modularity has been shown in this paper. Comparing costs with modularity is essential since cost is a major factor in the success of a product. Any design change made to improve retirement modularity will be practical only if the benefits accrued from an environment-friendly design are coupled with decreased costs due to the design change. One question that remains to be addressed is — do improvements in product modularity always decrease retirement costs? In this paper, an existing modular design method was focused on product retirement. Our initial study of the modularity-cost relationship is based upon the retirement of a consumer flashlight. We took a single flashlight and redesigned it, making it more modular, using a modular design method. The method has a set of guidelines helping in direct product development towards modular products. These are: 1. Eliminate the modules if they are not necessary. 2. Eliminate individual components of the modules. 3. Shift die components to other modules to increase the relative modularity of the product. 4. Redesign the attributes of the components to decrease or eliminate similarities or dependencies with outside components or increase similarities with components of the same module. After completing the modular design method, we measured the product modularity and retirement cost of the product at each intermediate stage of redesign. Costs associated with retirement including, recycling, reuse, remanufacturing, and disposal were measured at each stage using the cost equations listed below. The result of the research in this paper is studying the relationship between measured retirement modularity and product retirement costs. Statistical analysis of the flashlight data was carried out to look at the relationships between relative modularity, number of design changes made, and retirement cost. Our initial study of the relationship between product modularity and product retirement costs showed several trends. As was the hypothesis of this work, as product modularity and retirement modularity increase, product retirement costs tend to decrease. However, this trend is not as strong as previous literature has assumed. Our study of this hypothesis was complete but limited in scope. We have begun follow on research that expands this work to additional products and additional life-cycle stages.

Influence of Design Representation on Effectiveness of Idea Generation

The issue being investigated is the role of the type of representation used for recording design ideas in idea generation techniques for conceptual design. An empirical study was conducted to test the hypothesis that graphical (pictorial) representation is better than textual (sentential) for recording of design ideas. This study used a standard set of outcome measures: fluency, quality, novelty, and variety of ideas generated by use of different representations. The expressiveness of each representation was also studied by examining the ability to convey key design information of an idea. The experiment was designed and data analyzed based on the principles of statistical DOE. The study confirms the hypothesis that graphical representation provide greater benefits for engineering design idea generation than textual representation.

An Approach to Decision-Based Design

In this paper, we present the importance of using a single-criterion approach to Decision-Based Design (DBD) by examining the flaws and limitations of multicriteria approaches. We propose in this paper an approach to DBD as an enhancement to Hazelrigg’s DBD framework that utilizes the economic benefit to the producer as the single criterion in alternative selection. The technique of Discrete Choice Analysis (DCA) is introduced for constructing a product demand model, which is crucial for the evaluations of both profit and production cost. An academic universal motor design problem illustrates the proposed DBD approach. It appears that DBD, when applied correctly, is capable of unambiguously selecting the preferred alternative in a rigorous manner. Open research issues related to implementing the DBD approach are raised. The focus of our study is on demonstrating the approach rather than the design results per se.

Transformation of an EGT Grammar: New Grammar, New Designs

Grammars generate design options through the application of predefined rules that transform collections of symbols into more meaningful expressions. Research on the nature of grammars tells us that writing the rules is where the fundamental design activity occurs. Using the grammar rules allows us to explicitly articulate one design at a time. We can exploit the design power of grammars further by modifying a grammar to describe new languages of designs. Here we examine an existing grammar to demonstrate how modifying its rule base to relax an assumption can expand the space of solutions it generates significantly. We show that investing our design attention on the grammar itself can yield dramatic results.

A Methodology for Reusing Freeform Shape Content

The reuse of precedent designs is a significant profit factor in new product development. In industry there is a tendency to enhance the reuse process by applying digital scanning of 3D parts, sampling imported, normative CAD models or by deploying a digital library of design concepts. The data thus obtained should be inserted into the design model. The available techniques typically originate from reverse engineering applications. However, to support shape reuse during conceptual design a dedicated methodology and workflow are needed. Using our methodology, the designer selects existing products, or parts, or portions of them. Then he/she specifies where and how the selected portion should be inserted into the new design. The key issue of the methodology is the explicit distinction between the variables that the designer does or does not wants to control. The underlying technology, including shape matching, shape parameter fitting and shape merging must be mostly invisible to the user, except for those controls that intrinsically affect the resulting shape. One application of the methodology is a freeform feature copy-and-paste facility based on 3D scanning and fitting of existent designs. The technical feasibility of such an approach will be addressed.

Orchestrating Learning in a Graduate Engineering Design Course

ME6101: Engineering Design is a graduate level course offered by The George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. The course is orchestrated to achieve three objectives, namely, to have students internalize the Pahl and Beitz design method, to help them “reinvent” the Pahl and Beitz design method to meet the challenges of the future, and most importantly, to learn how to continue learning about design. The course was given during the Fall 2000 semester to a class of nineteen students — most in their first semester of graduate school — in addition to six practicing engineers via a distance-learning program. In this paper, the techniques utilized to foster learning in ME6101 are described. Excerpts from students’ essays are presented as anecdotal evidence that the concerted use of these methods aids students both in the internalization of course content and the development of personal practices that will serve them well in and beyond their engineering careers.