Carolyn Conner Seepersad

Balancing Commonality and Performance within the Concurrent Design of Multiple Products in a Product Family

Product family design involves the concurrent design of multiple products based on a common product platform to satisfy a variety of markets. The success of the resulting product family relies heavily on properly balancing the commonality of the product platform with the individual product performance within the product family. To help resolve this tradeoff, we present the Product Variety Tradeoff Evaluation Method for assessing alternative product platform concepts with varying levels of commonality. Two examples are presented to demonstrate the proposed method at both the detailed and the early stages of design. The redesign of a planetary gear transmission for a family of four cordless drills demonstrates the use of the method in the detailed stages of design, while the design of a family of three General Aviation Aircraft demonstrates the use of the method in the preliminary stages of design. The emphasis in this paper is on the effectiveness of the proposed method in evaluating this tradeoff and not on the results of the examples, per se.

Robust Design for Multiscale and Multidisciplinary Applications

The intent in robust design is to improve the quality of products and processes by reducing their sensitivity to variations, thereby reducing the effects of variability without removing its sources. Robust design is especially useful for integrating information from designers working at multiple length and time scales. Inevitably this involves the integration of uncertain information. This uncertainty is derived from many sources and robust design may be classified based on these sources-uncertainty in noise or environmental and other noise factors (type I); uncertainty in design variables or control factors (type II); and uncertainty introduce by modeling methods (type III). Each of these types of uncertainty can be mitigated by robust design. Of particular interest are the challenges associated with the design of multidisciplinary and multiscale systems; these challenges and opportunities are examined in the context of materials design.

Design of Multifunctional Honeycomb Materials

Extruded metal honeycombs [linear cellular alloys (LCAs)] are designed for a multifunctional application that demands not only structural performance but also heat transfer capabilities. The manufacturing process for LCAs enables complex in-plane cell topologies that may be tailored to achieve desired functionality. As a result, certain mechanical and heat transfer properties of LCAs are superior to those of hexagonal honeycombs or stochastic metal foams. Both periodic and functionally graded LCAs are designed for a structural heat transfer device for an electronic cooling application. The design problem is formulated as a multiobjective decision. Approximate models of structural and heat transfer performance, such as finite difference heat transfer simulations, are employed to analyze designs efficiently. A portfolio of heat exchanger designs is generated with both periodic and functionally graded cell topologies. Tradeoffs are assessed between thermal and structural performance. Previous authors have focused primarily on analysis of the structural and thermal properties of cellular materials; here, a design perspective is adopted. Given a set of rigorous analytical models, the emphasis is on synthesis of cellular designs and identification of superior design regions.

ROBUST DESIGN OF CELLULAR MATERIALS WITH TOPOLOGICAL AND DIMENSIONAL IMPERFECTIONS

A paradigm shift is underway in which the classical materials selection approach in engineering design is being replaced by the design of material structure and processing paths on a hierarchy of length scales for multifunctional performance requirements. In this paper, the focus is on designing mesoscopic material topology—the spatial arrangement of solid phases and voids on length scales larger than microstructures but smaller than the characteristic dimensions of an overall product. A robust topology design method is presented for designing materials on mesoscopic scales by topologically and parametrically tailoring them to achieve properties that are superior to those of standard or heuristic designs, customized for large-scale applications, and less sensitive to imperfections in the material. Imperfections are observed regularly in cellular material mesostructure and other classes of materials because of the stochastic influence of feasible processing paths. The robust topology design method allows us to consider these imperfections explicitly in a materials design process. As part of the method, guidelines are established for modeling dimensional and topological imperfections, such as tolerances and cracked cell walls, as deviations from intended material structure. Also, as part of the method,

A Quantitative Approach for Designing Multiple Product Platforms for an Evolving Portfolio of Products

Product variety can be provided more efficiently and effectively by creating families of products based on product platforms. One of the major advantages of the development of product platforms is the facilitation of an overall product development strategy, and an important factor in product development is the evolution of a family of products, including addition and retirement of products as well as changing demand and associated production quantities. In this paper, we present a quantitative approach for designing multiple product platforms for an evolving family of products. The approach is based on the utility-based compromise Decision Support Problem—a multi-objective decision support model with an objective function derived from utility theory. With this approach, a designer can model and consider multiple factors that influence the embodiment of product platforms as well as non-deterministic evolution of a portfolio of products serviced by the product platforms. We apply this approach to an example study of a family of absorption chillers, designed for a variable marketplace. Our emphasis is on the approach rather than the results, per se.© 2002 ASME

Designing for maintenance: A game theoretic approach

Maintenance management is the effective and economical use of resources to keep equipment in, or restore it to, a serviceable condition. In this paper, maintenance considerations are introduced during product design using a game theoretic approach. Specifically, a product designer and a maintenance manager are modeled as two players in a Leader-Follower game, and strategies for designing product components are derived accordingly. To implement this approach, the compromise Decision Support Problem, with a deviation function adapted from linear physical programming, is used to model decisions mathematically. This approach is intended for distributed collaborative design in which modeling, computational or organizational factors hinder complete integration of all aspects of a design problem. Using this approach, the knowledge and expertise of each designer are fully utilized while keeping modeling and computational challenges at a tractable level. The approach is illustrated with a case example, namely, the design of a series of absorption chillers for an industrial complex.

The characteristics of innovative, mechanical products

Many new products fail upon introduction to the marketplace, but a few products are exceptionally successful, earning innovation awards and other benchmarks of success. To better understand the features of those innovative products, 197 award-winning products are analyzed to identify the characteristics that distinguish those products from the competition. For the analysis, a set of product-level characteristics is identified and organized into categories, which include functionality, architecture, external interactions, user interactions, and cost. Based on their innovation award citations, the products are analyzed with respect to the set of characteristics, and results are tabulated. Several award-winning products are also compared with competitive products on the shelves of major retail stores. On average, award-winning products display multiple characteristics of innovation. Overall, a vast majority (more than two-thirds) of the award-winning products exhibit enhanced user interactions, with a similar percentage displaying enhanced external interactions, compared with approximately one-third of products offering an additional function and approximately half displaying innovative architectures. The award-winning products also exhibit an average of approximately two more characteristics than their competitors on retail shelves, along with significantly higher rates of innovative architecture, external interactions, and user interactions. The analysis concludes with a discussion of the implications of these findings for engineering design methods.

Empathic Lead Users: The Effects of Extraordinary User Experiences on Customer Needs Analysis and Product Redesign

An experiment was conducted to investigate the effectiveness of empathic lead user analysis for uncovering latent customer needs that could lead to breakthrough product ideas. Empathic lead users are defined as ordinary customers (or designers) who are transformed into lead users by experiencing the product in radically new ways, via extraordinary user experiences. These extraordinary experiences may include modifications of the usage environment or the way in which the customer interacts with the product. A procedure for designing and conducting empathic lead user interviews is introduced in this paper. Results are reported for a trial study in which the empathic lead user technique is compared with verbal and articulated use interviews for a common consumer product (a two-person tent). Empathic lead user interviews are observed to have a significantly positive effect on latent needs discovery in the trial study, leading to a five-fold increase in latent needs discovery relative to articulated use interviews with a prototype and a twenty-fold increase relative to verbal interviews without a prototype. Empathic lead user interviews emerge as a promising tool for supporting innovation and breakthrough concept generation.Copyright

Decision support in concurrent engineering - The utility-based selection decision support problem

Decisions are an important part of Concurrent Engineering and engineering design in general. Accordingly, more attention should be paid to the means and methods for making these decisions. In this article, a utility-based decision support method for the selection of an engineering design is presented. The utility-based selection decision support problem (u-sDSP) is a synthesized construct that facilitates selection decisions involving trade-offs among multiple, conflicting attributes and mitigation of risk associated with uncertain performance with respect to the attributes considered. The negative impact of unnecessary iterations on the product development cycle is reduced via the assurance of preference-consistent outcomes. Specifically, utility theory provides a mathematically rigorous means of clarifying and capturing designer preferences as well as identifying a preferred alternative in the context of stochastic uncertainty, while the selection decision support problem (DSP) – the construct within which utility theory is employed – facilitates the effective use of engineering judgment for (1) formulating and bounding decisions and (2) establishing a proper context. Application of the u-sDSP is illustrated with an example from rapid prototyping (RP), in which the goal is to select the appropriate technology and material combinations for testing the snap-fit design of a light switch cover plate assembly.

A comparison of the energy efficiency of selective laser sintering and injection molding of nylon parts

Purpose – The purpose of this paper is to evaluate the energy consumed to fabricate nylon parts using selective laser sintering (SLS) and to compare it with the energy consumed for injection molding (IM) the same parts.Design/methodology/approach – Estimates of energy consumption include the energy consumed for nylon material refinement, adjusted for SLS and IM process yields. Estimates also include the energy consumed by the SLS and IM equipment for part fabrication and the energy consumed to machine the injection mold and refine the metal feedstock required to fabricate it. A representative part is used to size the injection mold and to quantify throughput for the SLS machine per build.Findings – Although SLS uses significantly more energy than IM during part fabrication, this energy consumption is partially offset by the energy consumption associated with production of the injection mold. As a result, the energy consumed per part for IM decreases with the number of parts fabricated while the energy con...