STEPPED PULSE POWER SUPPLY AND FEEDRATE CONTROL FOR EDM OF MATERIALS WHICH ARE POOR CONDUCTORS Wollenberg, G. Schulze, H.-P. Timm, M Pape, Th. Summary The power converter system presented enables materials which are poor conductors to be machined with a constant discharge current. A spark starting power supply enables optimal sparking voltages to be adjusted. The power stages can be selected and deselected with a time lag, permitting any pulse shaping of the discharge current. A special pulse blanking-out feature is included to prevent maldischarge-induced damage to the component. The tailored feedrate control system employs the mean sparking delay time to identify the process behaviour. Thus, optimal gap width control is possible even if the terminal voltage varies during the machining of a component. Implementing this control system through a microcontroller entails the advantage that new control strategies better tailored to the process can be accomplished at any time. Moreover, owing to the high-degree flexibility of the controller, the settings of the latter can be selected to match the objective of machining. Tel.: 0049 391 67 12944 E-mail: Hans-Peter.Schulze@et.uni-magdeburg.de