| 主权项 |
1. An electric discharge machine configured to perform a hole machining on a workpiece by applying a voltage between an electrode and the workpiece to generate an electric discharge therebetween and moving the electrode to a position of a command depth, the electric discharge machine comprising:
a storage unit configured to store in advance therein a penetration determination voltage and a penetration determining duration used for determining whether the electrode has penetrated through the workpiece, a first projecting amount used for deciding a projecting amount of the electrode after penetrating through the workpiece, and the command depth, wherein said projecting amount accounts for consumption of the electrode during machining; a current-coordinate detection unit configured to detect a current position of the electrode; an electric-discharge-voltage detection unit configured to detect a voltage of the electric discharge during an execution of the hole machining; an electric-discharge voltage averaging unit configured to calculate an average voltage of the voltage of the electric discharge detected by the electric-discharge-voltage detection unit for each predetermined period; a penetration detection unit configured to determine, when a state where the average voltage calculated by the electric-discharge voltage averaging unit is higher than the penetration determination voltage continues for a time equal to or longer than the penetration determining duration, that the electrode has penetrated through the workpiece; and a calculation unit configured to calculate, at a time when the penetration detection unit determines that the electrode has penetrated through the workpiece, a position obtained by adding the first projecting amount to the current position of the electrode detected by the current-coordinate detection unit, and update the command depth stored in the storage unit with the calculated position, wherein when the command depth is updated, the electric discharge machine is configured to move the electrode from the current position to a position of the updated command depth, wherein the storage unit further stores in advance therein a verge-of-penetration determination value used for determining whether the electrode is in a verge-of-penetration state where the electrode starts to penetrate through the workpiece, and a second projecting amount used for deciding the projecting amount of the electrode after penetrating through the workpiece, the electric discharge machine further comprises: a deepest-position storage unit that stores a deepest position at which the electrode has approached closest to the command depth in the storage unit; and a verge-of-penetration-candidate-position determination unit that stores, when the current position detected by the current-coordinate detection unit is closer to the command depth than to a position obtained by adding the verge-of-penetration determination value to the deepest position stored in the storage unit, the current position in the storage unit as a verge-of-penetration candidate position, and when the verge-of-penetration candidate position is stored in the storage unit at the time when the penetration detection unit determines that the electrode has penetrated through the workpiece, the calculation unit updates the command depth stored in the storage unit with a position obtained by adding the second projecting amount to the verge-of-penetration candidate position. |
