Deformation at contacts between the workpiece and locators/clamps resulting from large contact forces causes overall workpiece displacement, and affects the localization accuracy of the workpiece. An important characteristic of a workpiece-fixture system is that locators are passive elements and can only react to clamping forces and external loads, whereas clamps are active elements and apply a pre-determined normal load to the surface of workpiece to prevent it from losing contact with the locators. Clamping forces play an important role in determining the final workpiece quality. This paper presents a general method for determining of the optimal clamping forces including their magnitude and positions. First, we develop a locally elastic contact model to describe the nonlinear coupling between the contact force and elastic deformation at the individual contact. Further, a set of "compatibility" equations are given so that the elastic deformations among all contacts in the w...