A yeN -To my wife Siew Kheng and daughters Joanne, Julianne, Suzanne for their patience and understanding KW -To Linda for all her help ASK -To my parents Prof Anantharajan and Ms Vijayalakshmi for their help and concern viii Preface are particularly indebted to those who have allowed us to reproduce parts of their work. We would also like to thank Imke Mowbray at Springer-Verlag for her help in coordinating the production of this book.

Commonly used models of the design process do not reflect concurrent engineering, the influence of computer-assisted design on the design process, or the recursive divergent-convergent thinking processes at different levels of detail from whole system to subsystem to component design. Also, these models do not illustrate the process of establishing functional integrity in the design of multicomponent systems where multiple interdependencies are present. This paper outlines design model developments by the authors and introduces a methodology for designing for system integrity and minimizing risk from early in the conceptual phase, where uncertainty is high. The process involves probabilistic reasoning in propagating both qualitative and quantitative effects of changes or uncertainty in component or subsystem specifications through system models and determining the integrity of the design from multiple viewpoints.

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A graph theoretical approach is presented that permits the calculation of optimal process plans from datum hierarchy trees, which are elegant representations of tolerance charts. The theory is developed for a cost function that minimizes machine and datum changes. Restrictions on the sequence of machining operations arising from technical constraints or the layout of a group cell are taken into account. The process plans are optimal with respect to a specified datum hierarchy tree, manufacturing constraints and cost function. It is shown that the number of possible plans for real industrial trees is very large, and therefore this kind of optimization is beyond the ability of a human process planner. Trial runs with industrial parts indicate that optimization can be performed by a computer within a time period that is acceptable for industrial use.

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