DECISION MONOTONICITY IN INCREMENTAL DESIGN - A CASE-STUDY OF DESIGN FOR MANUFACTURE

Design has often been described as searching the space of solutions to a given problem for either a feasible or optimal solution. Usually, t his search is conducted in an incremental, iterative manner. Unfortuna tely, there is a tendency, for the feasible space in some domains to e xhibit such pool structure that the incremental design process becomes both difficult and time consuming. This is especially true in the dom ain of design-for-manufacture by machining. In this paper we present t he view that in such cases the sour ces of ill-structure must be aggre ssively eliminated by making strategic improvements and modifications to the target technology. To illustrate this point, we show that the d omain of design-for-manufacture is ill-structured due to a class of in teractions known as global interactions. We then show how global inter actions can be virtually eliminated by a combination of a new workhold ing technology and a new interfacing technique. In the absence of glob al interactions, we show how the design structure exhibits a property of monotonicity. We describe the ramifications of this monotonicity on the design process, and show how design can then be considered to be deterministic. As a backdrop, we draw examples from other fields where similar strategies have resulted in greater 'designability'.