ELECTRIC DISCHARGE MACHINING APPARATUS

摘要

An electric discharge machining apparatus includes a power supply, an electrode gap formed from an electrode and a workpiece, a current limiting resistor connected between the power supply and the electrode gap, switching elements that turns on and off application of a voltage from the power supply to the electrode gap, an inductance element connected in series between the switching elements and the electrode gap, and a control unit that controls the switching elements. The control unit causes the switching elements to perform ON/OFF operations according to a switching pattern having an on-pulse time width (ΔTon) in which a voltage of the electrode gap can reach a voltage value of the power supply in an on-pulse time and a pause time width (ΔToff) equal to or longer than a time width (Δtic) of a discharge current flowing during the capacitor discharge and shorter than a cycle (ΔTso) of the self-excited oscillation.

主权项

1. An electric discharge machining apparatus that performs electric discharge machining, the electric discharge machining apparatus comprising:
a power supply; an electrode gap formed from an electrode and a workpiece; a current limiting resistor connected between the power supply and the electrode gap; switching elements that turn on and off application of a voltage from the power supply to the electrode gap; an inductance element connected in series between the switching elements and the electrode gap; and a control unit that controls the switching elements, wherein the electric discharge machining apparatus causes capacitor discharge, which makes use of capacitor capacitance of the electrode gap, to oscillate in a self-excited manner according to a circuit constant of an LCR circuit configured by the current limiting resistor, the inductance element, and the capacitor capacitance and performs machining, and the control unit causes the switching elements to perform ON and OFF operations according to a switching pattern having an on-pulse time width in which a voltage of the electrode gap can reach a voltage value of the power supply in an on-pulse time and the self-excited oscillation occurs two or more times and a pause time width equal to or longer than a time width of a discharge current flowing during the capacitor discharge and shorter than a cycle of the self-excited oscillation, and the control unit controls at least one of the on-pulse time width and the pause time width in the switching pattern such that the voltage of the electrode gap does not exceed the voltage value of the power supply because of energy contained in the inductance element.