VSS controller design for gap control of EDM

As an electrode quickly moves towards the discharge field, and then starts to discharge, the proposed variable structure system (VSS) with large switched proportional (P) gains can suddenly hold the electrode at the appropriate position. The erosion process can start quickly and stably in order to decrease the idle time of the whole eroding process. The design procedure of the VSS is presented according to a practical gap control system for an EDM. This advantage can provide high performance on the nonlinear and time-varying gap condition during eroding process. The practical experimental results of an EDM with the VSS controller show a decrease of the machining time, compared to the time required by the conventional proportional M controlled EDM.