Using CAD Geometric Variation Approach for Lettering Complicated Letter on 3D Free-Form Surface by a 3-DOF Parallel Machine Tool

A novel CAD geometric variation approach is proposed for machining a complicated shape workpiece and lettering on a 3D free-form surface or a plane by means of a 3-dofparallel machine tool. First, a simulation mechanism of a 3-DOF 3-SPR parallel manipulator is created, and its workspace is constructed by means of the 3-SPR simulation mechanism. Second, the tool path guiding plane and the simulation mechanism of the 3-dof 3-SPR parallel machine tool are combined to form a whole simulation mechanism. Third, the extension of the active legs and the position of the platform are solved automatically and can be visualized dynamically by means of the simulation mechanism. The simulation results are verified by the analytic results. The CAD geometric variation approach has the advantages of simple and straightforward, without any need of compiling program.