An integrated setup planning and fixture design system for prismatic parts

Abstract

This paper reports a knowledge–based system for conceptual and layout modular fixture design developed on an intelligent CAD system, ICAD. The integration of setup planning and fixture design is achieved through conceptual fixture design which includes two stages: the pre–setup and post–setup conceptual design. In the pre–setup stage, the system takes feature–based part models as input and generates feasible fixturing features for each possible setup based on static constraints only. This information is then used by a setup planning system developed separately. Post–setup conceptual fixture design takes place when the setup plan is available. For each setup with its intermediate workpiece state, the surface candidates for each fixturing datum are identified and ranked according to various geometric and technological constraints. The best ranked surface for each fixturing datum is selected. The system then performs layout design by generating all the supporting, locating and clamping points for each setup, taking into account various constraints including part geometry, stability, modular fixture elements, and interference. The series of setups are simulated graphically on the computer screen. Output from this system can be used for detailed fixture design. In this paper, the development of the system is described in detail and a case study is presented to highlight its performance.