Method and apparatus for controlling an electroerosion machining

Abstract

Two condition index variables are used for controlling operation in such a manner that one of the variables is kept as close as possible to a minimum value, while the other is held within an assigned range. Both condition index variables depend on the rate of flow of the flushing liquid through the working gap, on the interval between discharges in the gap or on the duty cycle or repetition frequency and amplitude of the discharge pulses. The condition index variable held to a minimum may be the integral of the square of the error signal from the regulating circuit of the electrode advancing drive, the integral of the square of the acceleration of electrode movement or the quotient obtained by dividing the square of the error signal by the square of the gap current. The regulating value to be held within an assigned range is a calculated breakdown potential defined by the relation of the variation of the error signal to the variation of the electrode spacing. The condition index variables are used to control the interval between discharges, the electrode spacing, the flow of flushing liquid, or other variables of the operation. Control of the flow of flushing liquid may be done directly where the liquid is supplied to the gap through holes in the workpiece or indirectly by intermittently backing off the electrodes to a controlled extent.