Set-based design systems for stampings and flexible fixture workspaces.

摘要

This thesis describes the development and test of two computational systems for supporting set-based concurrent engineering. They address two problems: (1) to formally represent and manipulate sets of shapes and (2) to automatically synthesize flexible fixture workspaces for a set of stampings. First, there are two approaches to designing products. One is to determine one design quickly and then make iterative changes to it. The other is to define a set of design alternatives in the beginning and to narrow the set as design proceeds. For example, Toyota informally employs the second approach by using many scaled clay models for exploring a design space, design tolerances for representing uncertainties, and lessons-learned books for representing manufacturable shapes. However, Toyota's informal approach relies on humans to imagine and interpret design spaces, and therefore it is inefficient and can cause misunderstandings. Thus, this thesis presents a set-based design system for shapes that enables product development team members to formally represent and manipulate sets of shapes using a computer. This system has been applied to designing stampings, and evaluated to be capable of representing most manufacturing requirements in stamping design handbooks. Second, fixtures are used to position and hold stampings for assembly. These fixtures conventionally have been dedicated and therefore they must be replaced whenever there are model changes. In recent years, however, auto companies increasingly use flexible fixtures, which are composed of robots as programmable fixture elements so that they can be reprogrammed for different stampings rather than being replaced. When designing flexible fixtures, fixture designers must be concerned with not only fixturing of one stamping but also fixture workspaces for a set of stampings. However, existing fixture design methods address fixturing of one stamping only. Thus this thesis presents a system to synthesize flexible fixture workspaces for a set of stampings. Based on circular workspaces for flexible fixture robots, this system finds optimal robot workspaces and their centers on the fixture plate and provides a graphical display for visual checking. This system has been tested with lab data and is effective because of its simplicity and short run time.