Assembly for Enhanced Repeatability Under Planar Constraints

In dies used to cure preformed material, the top die is actuated to significant force levels. To ensure repeatability, three external V-grooves are used to guide so that the two halves are located accurately in the plane perpendicular to the designed approach direction. The kinematics of this assembly process is revealed by analysis. Infinitesimal screw theory describing the instantaneous motion, or the velocity and the corresponding reciprocal space, that of the possible force system are used to characterize the motion of the top die. Dynamic simulation with force input equations governing the local trajectory of the top die as it progressively engages with the grooves is established. We record the excursion of the top die in the plane normal to the nominal approach direction to characterize the motion. The two die halves mating before the V-grooves form line contacts is seen to be a necessary condition for self-alignment. We show that on reassembly from randomly perturbed initial conditions, only on specific design of the V groove system, the CG is moved towards a fixed position by the nesting force.