Patent ID: 6169261
Filing Date: 2001-01-02
Classification: B23H

Abstract:
A method for generating an electric discharge for use in the line cutting of a workpiece, comprising the steps of: (1) performing a low-voltage ignition process at the discharge gap; if the total time of using the same polarity for ignition is still less than a preset time T.sub.4, then the current polarity for the next cycle of ignition is used; otherwise, inverting the polarity to the opposite; (2) detecting the polarity of the current low-voltage ignition; if negative, applying a negative ignition voltage to the electrode; otherwise, if positive, applying a positive ignition voltage to the electrode; (3) detecting the gap voltage at the discharge gap based on a first reference time T.sub.1 and a second reference time T.sub.2, where T.sub.1 <T.sub.2, and comparing the detected gap voltage V.sub.gap with a preset reference voltage range between a first reference voltage V.sub.ref1 and a second reference voltage V.sub.ref2 ; if during T.sub.1 the gap voltage V.sub.gap is within the range between V.sub.ref1 and V.sub.ref2, the indication is that the discharge gap is currently operating under arc discharging conditions; if during the period between T.sub.1 and T.sub.2 the gap voltage V.sub.gap is within the range between V.sub.ref1 and V.sub.ref2, the indication is that the discharge gap is currently operating under normal discharging conditions; and if beyond T.sub.2 the gap voltage V.sub.gap is still beyond the range between V.sub.ref1 and V.sub.ref2, the indication is that the discharge gap is currently operating under open-circuited conditions; (4) in the event of either normal or arc discharging conditions, applying the discharging voltage to the discharge gap for a predetermined on-time, and setting the arc-on-time to be half of the normal-on-time; and after the arc discharging is completed, switching off the discharging voltage for a predetermined off-time; and (5) in the event of open-circuited conditions, withholding the discharging voltage to be applied to the discharge gap for an off-time T.sub.3, and inverting the polarity for the next cycle of ignition where the ignition voltage is to be applied in an alternating direction.