A machining program creating device for a wire electric discharge machine creates a machining program for machining a keyway on the side surface of a round hole in a workpiece, based on a previously specified diameter of the round hole, a center position of the round hole measured by bringing a wire electrode into contact with the workpiece, and a previously defined shape of the keyway.

In wire-electrical discharge machine and a numerical control apparatus thereof and a numerical control apparatus for controlling a machine tool, optional minute blocks are automatically created in front of and behind a connecting point, i.e., a joint of a block to which an offset command is instructed, and an offset value is exchanged between the minute blocks so that a correct offset value is set in a desired block.

Whether or not an inter-electrode voltage exceeds a voltage threshold is determined after a predetermined inter-electrode state determination period has passed since application of an induction voltage (inter-electrode voltage) to an inter-electrode gap. Thus, an inter-electrode gap amount between a wire electrode and a work is estimated. A pause time during which electrical discharge is not performed is changed according to an estimation result of the inter-electrode gap amount.

Whether or not an inter-electrode voltage exceeds a voltage threshold is determined after a predetermined inter-electrode state determination period has passed since application of an induction voltage (inter-electrode voltage) to an inter-electrode gap. Thus, an inter-electrode gap amount between a wire electrode and a work is estimated. A pause time during which electrical discharge is not performed is changed according to an estimation result of the inter-electrode gap amount.

A replacement determination method: detects the remaining length of the electrode; detects the electrical discharge commencement position, being the position of the electrode when electrical discharge starts; detects the throughole position, being the position of the electrode when the workpiece is pierced; sets the required length for the electrode as required for machining the next throughhole, on the basis of the difference between the detected electrical discharge commencement position and the detected throughole position; compares the detected remaining length and the set required length; and determines whether or not electrode replacement is required.

A replacement determination method: detects the remaining length of the electrode; detects the electrical discharge commencement position, being the position of the electrode when electrical discharge starts; detects the throughole position, being the position of the electrode when the workpiece is pierced; sets the required length for the electrode as required for machining the next throughhole, on the basis of the difference between the detected electrical discharge commencement position and the detected throughole position; compares the detected remaining length and the set required length; and determines whether or not electrode replacement is required.

A power supply system for wire electric discharge machining includes a first power supply circuit and a second power supply circuit. The first power supply circuit applies, to the machining gap, a voltage that induces a discharge. The second power supply circuit, which includes a low inductance line, supplies a current, which contributes to the machining, to the machining gap,. A blocking diode is series-connected between the low inductance line and the machining gap. A container, which has a contact surface contacting with the blocking diode and contains a cooling liquid, is provided.

A power supply system for wire electric discharge machining includes a first power supply circuit and a second power supply circuit. The first power supply circuit applies, to the machining gap, a voltage that induces a discharge. The second power supply circuit, which includes a low inductance line, supplies a current, which contributes to the machining, to the machining gap,. A blocking diode is series-connected between the low inductance line and the machining gap. A container, which has a contact surface contacting with the blocking diode and contains a cooling liquid, is provided.

A primary power supply charges a capacitor by turning on a switching element and, upon completion of charging, turns off the switching element. Then, an AC pulse voltage is applied to the gap between a wire electrode and a workpiece by alternately turning on and off a switching element present in a secondary power supply. After a dielectric breakdown occurs between the wire electrode and the workpiece, the switching element is turned on to connect the capacitor so that the capacitor supplies a pulse current for machining.

When graphic information is selected, program creating unit receives machining shape data from graphic information analysis unit and pivot axis information from rotation center storage unit. Based on the received data, the program creating unit generates a new amount of movement of a wire electrode relative to a workpiece and the amounts of rotation of pivots, used to machine the workpiece with the wire electrode held vertical.