A simulated current generation unit is connected in series to a power supply device for an electric discharge machine in a state in which a contact and a contact are in contact with each other and generates a simulated current (I.sub.sim) for simulating current caused by dielectric breakdown of a discharge gap constituted by a workpiece and a pipe electrode, which face each other with a predetermined gap in order to perform electrical discharge machining of the workpiece by a narrow-hole electric discharge machine, based on an applied voltage of the power supply device for an electric discharge machine. An NC device judges the presence or absence of an abnormality of the power supply device for an electric discharge machine based on the simulated current (I.sub.sim) detected by a current detection unit.

A wire electric discharge machine performs electric discharge machining on a workpiece by relatively moving a workpiece placed on a workpiece table and a wire electrode supported by upper and lower wire guides according to a machining program. The wire electric discharge machine comprises an interference determination unit configured to determine whether or not the top or bottom surface of the workpiece table interferes with the wire electrode at the height of the surface during the execution of the machining program.

In a wire electric discharge machine, a discharge delay time is used to classify the inter-electrode state into three categories; a short-circuit state, small-gap state, and large-gap state. Based on this classification, the magnitude of a machining current supplied from a main discharge circuit is determined. If the discharge delay time is zero (i.e., if no electric discharge is generated) after the lapse of a predetermined time since the start of the application of a machining voltage to an inter-electrode gap by an auxiliary discharge circuit, the inter-electrode gap is determined to be short-circuited by machining chips. Thereupon, a short-circuit machining current is supplied from the main discharge circuit to the inter-electrode gap to remove the machining chips. In this way, establishment of a complete short-circuit state is prevented so that the machining efficiency is improved to increase the machining speed.

An electrical machining method comprises machining a workpiece by an electrical machining device comprising an electrode; increasing a feedrate of the electrode at a first acceleration if a discharge current passing through the electrode and the workpiece is lower than a discharge current reference; and decreasing the feedrate of the electrode at a second acceleration if the discharge current is higher than the discharge current reference, wherein the second acceleration has an absolute value higher than that of the first acceleration.

A wire electrical discharge machine includes: a travelling route formed of multiple divisional regions, through which a wire electrode is fed by an auto wire feeding mechanism; and a memory storing failure evaluation reference data on the auto wire feeding for every divisional region. The wire electrical discharge machine detects failure of the auto wire feeding and locate the tip position of the wire electrode at the time of failure and causes a controller to determine whether to perform or stop retry of the auto wire feeding based on the located tip position and the failure evaluation reference data for every divisional region.

A wire electrical discharge machine includes a first voltage applying circuit, a second voltage applying circuit, and a switch controller. The first voltage applying circuit includes a first DC power source for applying a positive polarity voltage across an electrode gap, and a first switch for on/off-switching of application of the positive polarity voltage. The second voltage applying circuit includes a second DC power source for applying a reverse polarity voltage to the electrode gap, and a second switch for on/off-switching of application of the reverse polarity voltage. The switch controller controls the first switch and the second switch so that the first switch and the second switch are not turned on simultaneously. The first DC power source and the second DC power source are set up so that the absolute value of the reverse polarity voltage is lower than the absolute value of the positive polarity voltage.

A wire electrical discharge machine obtains position error information indicating a position error in a planar direction in a workpiece placed on a mounting table after relative positions between a first guide unit and a second guide unit are changed, and calculates a position of the workpiece with the corrected position error in the planar direction in a state where a wire electrode is inclined according to an inclined state of the workpiece by using this position error information.

A wire electrical discharge machine is configured to perform removal machining of a workpiece by applying a voltage to a machining gap between a wire electrode and the workpiece through a feeder to generate electrical discharge and is provided with a feeder deterioration detection unit configured to detect deterioration of the feeder. The feeder deterioration detection unit includes a detection unit configured to detect a machining current value during the machining and a detection unit configured to detect the number of electrical discharges during the machining.

In a wire electric discharge machine of the present invention, a control variable detection apparatus is an inter-pole voltage detection apparatus and detects an average inter-pole voltage as a control variable correlating with an inter-pole distance. The wire electric discharge machine comprises a machining feed speed calculation apparatus determining a machining feed speed on the basis of a deviation between target voltage set by a target value setting apparatus 7 and the average inter-pole voltage so as to eliminate the deviation. The wire electric discharge machine further comprises a feed speed distribution apparatus and a relative movement apparatus. The inter-pole distance can be kept constant by the relative movement of a wire electrode and a workpiece made on the basis of a command of thus determined machining feed speed.

A double resistor-capacitor discharge machining system comprises an electrode, a discharge circuit module and a control unit. The electrode is configured to process a workpiece. The discharge circuit module comprises a first discharge circuit and a second discharge circuit. The first discharge circuit comprises a first resistor, a first capacitor and a first transistor and configured to generate a first discharge current. The second discharge circuit is connected in parallel with the first discharge circuit and includes a second resistor, a second capacitor and a second transistor to generate a second discharge current. The capacitance value of the first capacitor is greater than that of the second capacitor. The control unit is configured to respectively control the first transistor and the second transistor, and control the discharge circuit module to alternatively output the first discharge current and the second discharge current to the electrode.