Abstract: A discharge machining apparatus includes an electrode disposed in confronting relation to a workpiece with an insulative machining solution interposed therebetween for machining the workpiece by an electric discharge generated across an interelectrode gap between the electrode and the workpiece, a detector device for detecting a distribution of times to generate the discharge across the interelectrode gap after a voltage has been applied thereacross, and interelectrode condition discriminator for comparing a distribution of times as detected by the detector means after the voltage has been applied across the interelectrode gap and before the discharge is generated thereacross to produce a signal indicative of a determined condition of the interelectrode gap.

Abstract: A wire electrical discharge machining apparatus capable of adequately ascertaining whether the condition of the machining gap is good or bad without lowering the machining speed while preventing damage to the wire electrode. The apparatus includes a high-frequency voltage source that supplies voltage to the gap between applications of DC voltage machining pulses. In response to the application of high-frequency voltage to the gap a current detector and two voltage comparators detect the degree of electric insulation (i.e. dielectric strength) of the machining liquid in the gap. The condition of the gap is determined based upon comparison between the detected degree of electric insulation and a predetermined reference value. In response to the determined condition of the machining liquid gap conditions such as the machining pulse shape, gap width, wire tension, wire feed rate, rate of renewal of the machining liquid, and resistivity of the machining liquid may be changed.

Abstract: A voltage sensor senses the gap voltage between an electrode and a conductive workpiece and compares it to a reference voltage using a comparator amplifier. The output from the comparator amplifier is used by an oil hydraulic servomechanism to raise and lower the electrode. An ultrasonic sensor detects impulse waves from discharges and a current sensor detects the working current for determining the working conditions of the gap. After a predetermined number of irregular discharges occurs the gap width may be widened by the servomechanism, the flow of dielectric fluid may be increased to remove sludge and debris, or the time between machining pulses may be increased.

Abstract: In an electric discharge machine including an electrode and a workpiece installed opposite each other with an insulating working liquid filling the gap therebetween and which is used to machine the workpiece by causing an electric discharge across the gap, two components of the frequency spectrum of the voltage waveform of the electric discharge across the electrode and the workpiece are analyzed to distinguish between normal and abnormal discharge conditions. The device includes elements for determining the conditions in the gap and which generate a signal according to the conditions of the interpole gap, based on the results of this analysis. When an abnormal condition exists, the size of the interpole gap may be changed, and the quiescent time between application of pulse voltages may be altered. Also, depending on the degree of abnormality, different quantities of dielectric fluid may be pumped through the interpole gap to remove accumulated impurities.

Abstract: A wire type electric discharge machining device monitors the location of discharges occurring within the gap between a wire electrode and workpiece. The location is determined as a function of the inductance between the discharge point and the power supply, which inductance is determined by examining the discharge current waveform. When an excessive number of consecutive discharges occur at the same location in the gap, the device regulates the value of the pulse voltage applied to the machining gap, or the quiescent time thereof.