Comparison on linear synchronous motors and conventional rotary motors driven Wire-EDM processes

Motion control of electrical discharge machining (EDM) processes is getting improved in recent years on both drive types and their control performance. This paper aims at comparison of the Wire-EDM's performance between driven by linear synchronous motors (LSM) and that by conventional rotary motors associated with ball-screw. Mathematical models of both drive types are derived and their parameters are identified through standard procedures. Then some theoretical characteristics are revealed, and the models are verified through conducted experiments. Since both drives are equipped with optical linear scales of sub-micrometer resolution, the measurements are compared on the same level. Specific phenomena such as wear and transmission stiffness of ball-screw driven table and cogging force of direct LSM driven table are discussed. Then the machining errors occurred in corners and arcs cutting, and meso-scaled parts are compared in the Wire-EDM processes. Experimental results showed that the accuracy and deviation outcomes with direct drive are much better than those with conventional drive, especially in high feed rate and around points where feed direction was changed.