Fixture planning with friction

A fixture planning module is being developed as part of a computational system for concurrent product and process design. The module employs symbolic and numerical analyses at different levels of detail, from fast geometric checks to more time consuming force and friction analyses, depending on the completeness of the machining plan. In this paper we focus on the approaches used for analyzing fixture kinematics and clamping forces, including the analysis of friction. Since many fixture arrangements rely on friction to hold a part, the ability to reason about friction is an important component of fixture planning. Limit surfaces in force/moment space are introduced as a convenient formalism to check whether parts will slip and to help in specifying clamping forces.