Concurrent design of machined products: a multivariate decision approach

In the traditional process of product design, a sequential approach treats each of the design steps individually without considering requirements of manufacturing, assembly and other downstream activities in the product life cycle. The lack of systematic and simultaneous consideration on the impact of design decisions on manufacturing and assembly leads to repeated and excessive changes in design and processes. To resolve this problem, the concurrent engineering approach to product design foresees and avoids potential design flaws by incorporating design requirements from downstream activities of the product development life cycle early in the design stage. This research develops a methodological framework for product life cycle design in concurrent engineering. Through a cohesive organization of semantics of high-level design features and relationships, this representation provides a means to evaluate the impact of design on subsequent activities in the product life cycle, including design for manufacture (DFM), design for assembly (DFA), and design for productivity (DFP). In the first stage of a two-level design, selection of design candidates is made based on multiple design criteria using utility theory taking into account imprecision of design information and user preference. The second stage of design further fine-tunes attribute values of the selected design by a genetic algorithm based parametric optimization procedure. An illustrative example of two alternative designs of a milling fixture demonstrates the effectiveness of the framework and its implementation methodology.