Bert Bras

Designing Design Processes in Decision-Based Concurrent Engineering

We believe that the efficiency and effectiveness of human designers can be improved by making available tools that can be used to help negotiate solutions to open or unstructured parts of the process of designing. We assert that the efficiency and effectiveness of a designer can be increased by increasing the speed with which the design iteration is accomplished and reducing of the number of iterations. An increment in the iteration speed can be achieved if at least some parts of a design process are known and can be modelled on a computer. One way of reducing the number of iterations in design is by avoiding this corrective redesign. This provides the stimulus for developing approaches to design that include Concurrent Engineering considerations. Thus, in our opinion, a necessary ingredient in increasing efficiency and effectiveness of human designers is the modeling of design processes in a manner that they can be analyzed, manipulated and implemented. This is the central theme of our paper. OUR FRAME OF REFERENCE PROBLEM IDENTIFICATION Often flaws in the solution of a design problem are detected during manufacture and even maintenance. The corrective redesign effort is usually extremely expensive and ideally should be have been “designed out” prior to manufacture. The effort to reduce such costly iterations has provided the stimulus for developing approaches to design that include life cycle considerations (that is, design, manufacture and support). Approaches to design that incorporate life cycle considerations include Concurrent Engineering [13]*, simultaneous engineering, Unified Life Cycle Engineering (ULCE) [4-7], producibility engineering [8]. Companies that have made use of some of these approaches have reported impressive benefits [3]. Our primary interest is in developing the capabilities for a team of human designers to design concurrently in the early stages of project initiation. Why? Dierolf and Richter in the conclusion of a recent study for the Institute of Defense Analysis state [6]: “The importance of early design decisions is widely recognized. It is often stated that roughly 70 percent of the total life cycle cost of the system is determined during the conceptual phase. Due to the lack of hard data, very few traditional CAD tools are available to support the early stages of design. Considering the high leverage of the decisions made during these stages, this is an undesirable situation.” * Numbers in parentheses designate references at end of paper. * Numbers in parentheses designate references at end of paper.

A decision-based approach to concurrent design

Modern, computer-based concurrent design requires a holistic approach that integrates the representation, management and processing of information. Integration is possible through the ‘standardization’ of information management within a design process. We approach standardization from the perspective of decision-based design (DBD), namely, that ‘the principal role of an engineer, in the design of an artifact, is to take decisions’. Given that decisions are foundational, we enable concurrent design processes through the simultaneous analysis, synthesis and resolution of multiple decisions.

Selection Without Reflection is a Risky Buisness ...

In engineering, designers are often faced with decisions involving conflicting objectives. Although existing Multi Criteria Decision Making (MCDM) “methods” can aid decisionmakers in satisfying the required trade-offs, a basic understanding of the assumptions and limitations underlying the approaches is required. It is important to note that all of these so called MCDM “methods” have fundamental shortcomings, which render them inappropriate for carte blanche application. Making an educated decision, as to which method to choose for a particular problem, however, is confounded by the fact that over 70 MCDM methods have thus far been proposed within the literature. Although many approaches, aimed at facilitating the selection of the most suitable MCDM approaches for a particular task, have been proposed, these are misleading since they suggest the existence of a “best” method for a particular problem at hand. The very description of the MCDM techniques as methods is a misnomer, as the majority of them constitutes nothing more than attention directing tools and should be treated as such -with caution. Nevertheless, these attention directing tools, when used appropriately in a proper context, may have a significant amount of utility. It is for this reason that we advocate careful reflection (with regard to the problem at hand, the underlying assumptions/limitations of the attention directing tool considered, and interpretation of results) before selection.