Static interactions of surface contacts in a fixture–workpiece system

Abstract

Static indeterminacy and frictional constraint nonlinearity are common problems encountered in fixture configuration design. In a fixture–workpiece system, the behaviour of contact is influenced by a combination of geometrical, kinematic and elastic relationships. Our objective is to determine clamping force intensities for a given layout of fixels by investigating contact force distribution. In this paper, we present a numerical procedure to accurately determine clamping forces required to satisfy fixturing requirements with good computational efficiency. A system of virtual springs is used to illustrate the states of contact restraints at locating and clamping points. The differences between manual clamping and power clamping are investigated and analysed theoretically. A cone set of virtual springs is introduced to model a frictional contact. We then develop a linear programming model to find a set of minimum clamping force intensities, and to identify their feasible directions for increments. Examples are also given to demonstrate the procedure.