wire electric discharge

A wire electric discharge machining according to the embodiments includes: an electrode wire, a wire feed unit that supplies the wire electrode, a take-up motor, which receives the electrode wire at a predetermined speed, a tensioning motor that controls a voltage of the electrode wire between the wire feeding unit and the take-up motor, a speed calculating unit, calculates a traveling speed of the wire electrode at a predetermined time interval, a speed storage unit which stores the value calculated by the speed calculation unit running speed, a speed difference calculating unit that calculates a speed difference between an output from the speed calculating unit, the current running speed and a stored in the speed memory unit, the former running speed; and a break detecting unit, the breaking of the wire electrode detected by comparing the difference with a predetermined threshold speed.