Analysis of the effects of fixture clamping sequence on part location errors

Several fixture-related error sources are known to contribute to part location error, which can lead to poor part quality. In addition to typical error sources, such as fixture geometric error and elastic deformation of the fixture and part due to clamping forces, the clamping sequence used can also influence part position and orientation. In this paper, the effect of clamping sequence on workpiece location error is modeled analytically for a fixture–workpiece system where all major compliance sources and fixture geometric error are considered. Part location error is quantified by the displacement of a response point on the part surface. An algorithmic procedure designed to understand how forces and deformations change as clamps are applied sequentially is presented. The effect of clamping sequence on part location error and locator reaction force is examined through model simulations and experiments via an example involving a 3-2-1 machining fixture.