Wire electric discharge machine capable of detecting machining state and determining average voltage in machining gap

1. A wire electric discharge machine capable of detecting a machining state and determining an average voltage in a machining gap between a wire electrode and a workpiece, comprising:

a voltage application unit configured to apply positive and negative voltages to the machining gap for a period of one microsecond or less with an off time equal to or longer than a voltage application time set during each cycle of voltage application;

a machining-gap voltage detection unit configured to detect a machining-gap voltage produced in the machining gap;

an application cycle number counting unit configured to count for each unit time the number of application cycles of the voltages applied by the voltage application unit;

an open-circuit determination unit configured to determine an open-circuit state in which electric discharge does not occur after a predetermined open-circuit determination voltage level is reached or surpassed by the machining-gap voltage detected by the machining-gap voltage detection unit;

an open-circuit number counting unit configured to count for each unit time the number of voltage application cycles determined to be in an open-circuit state by the open-circuit determination unit, as an open-circuit number;

an electric discharge determination unit configured to determine an electric discharge state in which electric discharge occurs after a predetermined electric discharge determination voltage level is reached or surpassed by the machining-gap voltage detected by the machining-gap voltage detection unit, then the machining-gap voltage becomes lower than the electric discharge determination voltage level; and

a discharge number counting unit configured to count for each unit time the number of voltage application cycles determined to be in an electric discharge state by the electric discharge determination unit, as a discharge number,

wherein the average voltage in the machining gap is determined based on a first predetermined voltage corresponding to the machining-gap voltage in the open-circuit state, a second predetermined voltage corresponding to the machining-gap voltage in the electric discharge state, the number of voltage application cycles per unit time counted by the application cycle number counting unit, the open-circuit number per unit time counted by the open-circuit number counting unit, and the discharge number per unit time counted by the discharge number counting unit.

2. The wire electric discharge machine according to claim 1 , wherein the average voltage in the machining gap is calculated as follows:

Average machining-gap voltage={(open-circuit number×first predetermined voltage)+(discharge number×second predetermined voltage)}/(application cycle number).

3. The wire electric discharge machine according to claim 1 , wherein at least one of the determination voltage levels for the determination of the open-circuit state and the electric discharge state is variable depending on a power supply voltage of the voltage application unit, a workpiece thickness, a wire diameter, and/or a workpiece material.

4. The wire electric discharge machine according to claim 1 , wherein at least one of the first and second predetermined voltages is variable depending on a power supply voltage of the voltage application unit, a workpiece thickness, a wire diameter, and/or a workpiece material.

5. A wire electric discharge machine capable of detecting a machining state and determining an average voltage in a machining gap between a wire electrode and a workpiece, comprising:

a voltage application unit configured to apply positive and negative voltages to the machining gap for a period of one microsecond or less with an off time equal to or longer than a voltage application time set during each cycle of voltage application;

a machining-gap voltage detection unit configured to detect a machining-gap voltage produced in the machining gap;

an application cycle number counting unit configured to count for each unit time the number of application cycles of the voltages applied by the voltage application unit;

an open-circuit determination unit configured to determine an open-circuit state in which electric discharge does not occur after a predetermined open-circuit determination voltage level is reached or surpassed by the machining-gap voltage detected by the machining-gap voltage detection unit;

an open-circuit number counting unit configured to count for each unit time the number of voltage application cycles determined to be in an open-circuit state by the open-circuit determination unit, as an open-circuit number;

an electric discharge determination unit configured to determine an electric discharge state in which electric discharge occurs after a predetermined electric discharge determination voltage level is reached or surpassed by the machining-gap voltage detected by the machining-gap voltage detection unit, then the machining-gap voltage becomes lower than the electric discharge determination voltage level;

a discharge number counting unit configured to count for each unit time the number of voltage application cycles determined to be in an electric discharge state by the electric discharge determination unit, as a discharge number;

a short-circuit determination unit configured to determine a short-circuit state in which a predetermined short-circuit determination voltage level is not reached or surpassed by the machining-gap voltage detected by the machining-gap voltage detection unit during 1 cycle of the voltage application; and

a short-circuit number counting unit configured to count for each unit time the number of voltage application cycles determined to be in a short-circuit state by the short-circuit determination unit, as a short-circuit number,

wherein the average voltage in the machining gap is determined based on a first predetermined voltage corresponding to the machining-gap voltage in the open-circuit state, a second predetermined voltage corresponding to the machining-gap voltage in the electric discharge state, a third predetermined voltage corresponding to the machining-gap voltage in the short-circuit state, the number of application cycles per unit time counted by the application cycle number counting unit, the open-circuit number per unit time counted by the open-circuit number counting unit, the discharge number per unit time counted by the discharge number counting unit, and the short-circuit number per unit time counted by the short-circuit number counting unit.

6. The wire electric discharge machine according to claim 5 , wherein the average voltage in the machining gap is calculated as follows:

Average machining-gap voltage={(open-circuit number×first predetermined voltage)+(discharge number×second predetermined voltage)+(short-circuit number×third predetermined voltage)}/(application cycle number).

7. The wire electric discharge machine according to claim 5 , wherein at least one of the determination voltage levels for the determination of the open-circuit state, the electric discharge state, and the short-circuit state is variable depending on a power supply voltage of the voltage application unit, a workpiece thickness, a wire diameter, and/or a workpiece material.

8. The wire electric discharge machine according to claim 5 , wherein at least one of the first to third predetermined voltages is variable depending on a power supply voltage of the voltage application unit, a workpiece thickness, a wire diameter, and/or a workpiece material.

9. A wire electric discharge machine capable of detecting a machining state and determining an average voltage in a machining gap between a wire electrode and a workpiece, comprising:

a voltage application unit configured to apply positive and negative voltages to the machining gap for a period of one microsecond or less with an off time equal to or longer than a voltage application time set during each cycle of voltage application;

a machining-gap voltage detection unit configured to detect a machining-gap voltage produced in the machining gap;

an application cycle number counting unit configured to count for each unit time the number of application cycles of the voltages applied by the voltage application unit;

a short-circuit determination unit configured to determine a short-circuit state in which a predetermined short-circuit determination voltage level is not reached or surpassed by the machining-gap voltage detected by the machining-gap voltage detection unit during 1 cycle of the voltage application; and

a short-circuit number counting unit configured to count for each unit time the number of voltage application cycles determined to be in a short-circuit state by the short-circuit determination unit, as a short-circuit number,

wherein the average voltage in the machining gap is determined based on a fourth predetermined voltage corresponding to the machining-gap voltage in the open-circuit state and the electric discharge state, the number of application cycles per unit time counted by the application cycle number counting unit, and the short-circuit number per unit time counted by the short-circuit number counting unit.

10. The wire electric discharge machine according to claim 9 , wherein the average voltage in the machining gap is calculated as follows:

Average machining-gap voltage=(application cycle number−short-circuit number)×(fourth predetermined voltage)/(application cycle number).

11. The wire electric discharge machine according to claim 9 , wherein the determination voltage level for the determination of the short-circuit state is variable depending on a power supply voltage of the voltage application unit, a workpiece thickness, a wire diameter, and/or a workpiece material.

12. The wire electric discharge machine according to claim 9 , wherein the fourth predetermined voltage is variable depending on a power supply voltage of the voltage application unit, a workpiece thickness, a wire diameter, and/or a workpiece material.