Product property margins: an underlying critical problem of engineering design

Eckert, Claudia; Isaksson, Ola and Earl, Christopher (2012). Product property margins: an underlying critical problem of engineering design. In: Proceedings of TMCE 2012, pp. 1027–1040.


Engineering change occurs throughout the entire product life cycle. Change propagation can lead to unexpected effort and the objective of this paper is to help manage these changes. Propagation depends on the margins for change allowed in individual parameters. The paper examines these parameter margins for components in complex aerospace products. The main objective is to understand how margins are managed in a design process both within a single product development but across product generations within and outside platforms. The results indicate that parameter margins appear in different forms and are only understood by practitioners to a limited extent. This paper shows the critical importance of parameter margins in understanding, managing and predicting changes, both for engineering and for long term product planning, where sequences of changes are considered over generations of the product and associated product platforms. A main conclusion is to propose that design methods use a 'classification' of margin/change types when defining design concepts. Interfaces and associated dependencies are then classified with respect to change sensitivity in order to enable better predictability of effects when changes are made. This offers one route to embodying the 'good judgment' of experienced designers into design methods. This approach represents a design technique tailored to synthesis rather than analysis.

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