Patent ID: 8829383

Claim:
A wire electric discharge machine that applies a predetermined pulse voltage between a wire electrode and a workpiece, while moving the wire electrode relatively to the workpiece along a path programmed beforehand in a machining program for skim cuts, the wire electric discharge machine includes: a straight line portion instructing unit that outputs, when machining a straight line portion, to a servo amplifier a straight-line-portion-machining-feed-speed instruction specifying a machining feed speed for the straight line portion, an average speed calculating unit that calculates a straight-line-portion average speed for machining the straight line portion, a corner-portion detecting unit that looks ahead the machining program and outputs, if detecting a corner portion, corner-portion detection information about a corner portion's path, a volume ratio calculating unit that calculates, based on the corner-portion detection information, a machining volume ratio of a machining volume per a unit of distance at the corner portion to a machining volume per the unit of distance at the straight line portion, a corner-portion-machining-feed-speed calculating unit that calculates a machining feed speed for the corner portion as a product of the straight-line-portion average speed and an inverse of the machining volume ratio, a corner portion instructing unit that outputs, when machining the corner portion, to the servo amplifier, a corner-portion-machining-feed-speed instruction specifying the machining feed speed for the corner portion, wherein the machining volume per the unit of distance is an amount of a workpiece area removal when the wire electrode moves the unit of distance, from one point to another point on the programmed path, the machining volume per the unit of distance at the corner portion is equal to a portion of a sector delineated by a first arc and a second arc which have a central angle corresponding to a movement of the wire electrode from the one point to the another point on the programmed path, the first arc corresponds to the movement of the wire electrode from the one point to the another point on the programmed path in a previous cutting operation, and the second arc corresponds to the movement of the wire electrode from the one point to the another point on the programmed path in a current cutting operation.