Fanuc Corporation

Masao Murai

Akiyoshi Kawahara

Tomoyuki Furuta

Yasuo Nakashima

Akihiro Sakurai

Yasuo Arakawa

Masaki Kurihara

Masayuki Yoshida

In a power supply device for electric discharge machining, the polarity of the voltage to be applied is determined on the basis of a result of determination whether the machining gap is in open state or not, an average value of voltages applied across the machining gap voltage during machining, and the number of successive open states with the same polarity. This eliminates the need to significantly vary the voltages to be applied from positive to negative and from negative to positive, thereby reducing the output energy required by the machining power supply.

Power supply device for electric discharge machining

A voltage is applied to a machining gap between a wire electrode and a workpiece for a period of one microsecond or less with a quiescent time longer than the duration of voltage application between each two adjacent cycles of voltage application provided, and the number of duty cycles and a machining-gap voltage are detected. An open-circuit state in which electric discharge does not occur after the voltage is applied is identified by the detected machining-gap voltage, and the number of open-circuits is counted. An average machining-gap voltage is obtained based on the numbers of duty cycles and open-circuits and the supply voltage or an average voltage for each duty cycle.

Wire electric discharge machine capable of detecting machining state

An electric discharge machine includes a machining power supply for applying a voltage to a machining gap between a machining electrode and its opposite workpiece and detecting a contact between the machining electrode and the workpiece. The machining power supply includes a first power supply circuit whose output voltage is equal to or less than an arc voltage, a second power supply circuit for supplying a pulse current to the machining gap, and a control unit. When the first power supply circuit detects a contact between the machining electrode and the workpiece, the control unit operates to supply a pulse current from the second power supply circuit to the machining gap while the machining electrode and the workpiece are in contact with each other.

Electric discharge machine

In order to detect a machining state of a wire electric discharge machine, the state of a machining gap is classified into three categories; an open-circuit state in which electric discharge does not occur after a first predetermined level is reached or surpassed by a machining-gap voltage, an electric discharge state in which electric discharge occurs after a second predetermined level is reached or surpassed by the machining-gap voltage, whereby the machining-gap voltage becomes lower than the second predetermined level, and a short-circuit state wherein a third predetermined level is not reached or surpassed by the machining-gap voltage. An average voltage in the machining gap is determined based on voltages in these states and the number of cycles of voltage application to the machining gap, number of open-circuits, number of discharges, and number of short-circuits per unit time.

Wire electric discharge machine capable of detecting machining state and determining average voltage in machining gap

In a torque motor driving device for wire cut electrical discharge machines, a voltage waveform rectified by a full-wave rectifying circuit, not using a high-capacitance electrolytic capacitor, is applied as an AC voltage to a single-phase torque motor by a bridge circuit including semiconductor switches. A PWM signal whose duty is adjusted so that the current flowing through the torque motor matches an instructed value is generated and the generated PWM signal is used for the operation of the bridge circuit.

Torque motor driving device for wire cut electrical discharge machines

An electric discharge machining apparatus capable of precisely detecting the electric discharge in a case of performing machining by minute machining energy such as in finish machining. A voltage is applied between a tool electrode and a workpiece by repeating ON/OFF of a switching element to charge a stray capacitance between the electrodes to cause electric discharge between the electrodes by the charged voltage. The electric discharge between the electrodes in the electric discharge machining by the minute machining energy is detected. The current between the electrodes is detected by integrating an output of a sensor coil. An offset component superposed in the output of the integrator by a low-pass filter is extracted. The extracted offset component is eliminated from the output of the integrator by a differential amplifier. An output of the differential amplifier is compared with a reference value to detect the electric discharge.

Electric discharge machining apparatus

An electric-discharge-machining power supply device in which energy loss is hardly produced and a charge voltage of a capacitor is easily controlled. When a switching element SWis turned on, a capacitor C is charged via an inductor L. When the voltage Vc of the charged capacitor exceeds the voltage of a direct-current power source E, a current is returned to the power source E via a diode D. When the switching element SWis turned off, energy stored in the inductor L flows from the inductor L through the diode D, the power source E and the diode D, so that the voltage Vc of the capacitor C is kept at the power source voltage. When a switching element SWis turned on, the voltage of the capacitor is applied between an electrode and a workpiece.

Supply of a wire electrode, application of a detection voltage, and binarization and sampling of the detection voltage are started, so as to start advance of the wire electrode from the position A toward a workpiece. The position of the wire electrode when a sampling value (low level) is detected for the first time is designated as a position B, and the wire electrode is advanced from this position by a predetermined distance P1, and is stopped at a position C. Retreat of the wire electrode is started from the position C, and a position Q where the sampling value has changed from the high level to the low level is stored as a contact/noncontact boundary position. Further, retreat of the wire electrode is continued, and the wire electrode is stopped at a predetermined separating position D, to thereby finish the processing.

Wire contact/noncontact boundary position detecting apparatus of wire cut discharge machine

A power supplying device for an electric discharge machine prevents electric discharge by a voltage from a subsidiary power supply circuit during a delay time from generation of the electric discharge to a rise of a voltage from a main power supply circuit. A parallel circuit, of a current reducing resistor and a capacitor, is provided in series in the subsidiary power supply circuit. A controller turns on the subsidiary power supply circuit to apply a voltage between a first electrode and a workpiece, as a second electrode, to generate an electric discharge therebetween, electricity charging the capacitor flowing between the electrodes to maintain the electric discharge even if an electric discharge current oscillates. The controller further turns on a main power supply circuit to supply a machining current in response to detection of the electric discharge and the current reducing resistor suppresses any leakage current during the application of the voltage from the subsidiary power supply circuit.

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Yamanashi, Japan

Masao Murai