WIRE ELECTRIC DISCHARGE MACHINE CAPABLE OF DETECTING MACHINING STATE

• US 20120048833A1
• Filed: 06/02/2011
• Published: 03/01/2012
• Est. Priority Date: 08/26/2010
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: KAWAHARA, Akiyoshi, MURAI, Masao, FURUTA, Tomoyuki
• Granted Patent: US 8,975,554 B2
• Time in Patent Office: Days
• US Class Current: 219/69.13
• CPC Class Codes: B23H 1/022 for shaping the discharge pulse train B23H1/024 takes precedence
• CPC Class Codes: B23H 1/024 Detection of, and response to, abnormal gap conditions, e.g. short circuits preventing short circuits or other abnormal discharges by altering machining parameters using adaptive control B23H7/16
• CPC Class Codes: B23H 7/04 Apparatus for supplying current to working gap; Electric circuits specially adapted therefor

Abstract

A voltage is applied to a machining gap between a wire electrode and a workpiece for a period of one microsecond or less with a quiescent time longer than the duration of voltage application between each two adjacent cycles of voltage application provided, and the number of duty cycles and a machining-gap voltage are detected. An open-circuit state in which electric discharge does not occur after the voltage is applied is identified by the detected machining-gap voltage, and the number of open-circuits is counted. An average machining-gap voltage is obtained based on the numbers of duty cycles and open-circuits and the supply voltage or an average voltage for each duty cycle.

Claims

1. A wire electric discharge machine, which applies a high-frequency voltage to a machining gap between a wire electrode and a workpiece located at a predetermined distance from the wire electrode, thereby generating electric discharge to machine the workpiece, the wire electric discharge machine comprising:

voltage application means which applies a bipolar voltage to the machining gap between the wire electrode and the workpiece for a period of one microsecond or less with a quiescent time longer than the duration of voltage application between each two adjacent cycles of voltage application provided;

machining-gap voltage detection means for detecting a machining-gap voltage produced in the machining gap;

duty cycle number counting means for counting the number of duty cycles of the voltage applied by the voltage application means for each unit time;

open-circuit state identification means for identifying an open-circuit state where no electric discharge occurs after the voltage is applied, based on the machining-gap voltage detected by the machining-gap voltage detection means; and

open-circuit number counting means for counting the number of open-circuits identified by the open-circuit state identification means for each unit time,

wherein an average machining-gap voltage is obtained based on the number of duty cycles per unit time counted by the duty cycle number counting means, the number of open-circuits per unit time counted by the open-circuit number counting means, and a supply voltage or an average voltage for each duty cycle.

2. The wire electric discharge machine according to claim 1, wherein the open-circuit state identification means compares a full-wave-rectified machining-gap voltage waveform with a predetermined reference voltage within the quiescent time, identifies the open-circuit state if the reference voltage is exceeded, and identifies a closed-circuit state if the reference voltage is not reached, in contrast.

3. A wire electric discharge machine, which applies a high-frequency voltage to a machining gap between a wire electrode and a workpiece located at a predetermined distance from the wire electrode, thereby generating electric discharge to machine the workpiece, the wire electric discharge machine comprising:

voltage application means which applies a bipolar voltage to the machining gap between the wire electrode and the workplace for a period of one microsecond or less with a quiescent time longer than the duration of voltage application between each two adjacent cycles of voltage application provided;

machining-gap voltage detection means for detecting a machining-gap voltage produced in the machining gap;

duty cycle number counting means for counting the number of duty cycles of the voltage applied by the voltage application means for each unit time;

open-circuit state identification means for identifying an open-circuit state where no electric discharge occurs after the voltage is applied, based on the machining-gap voltage detected by the machining-gap voltage detection means; and

open-circuit number counting means for counting the number of open-circuits identified by the open-circuit state identification means for each unit time,

wherein an electric-discharge ratio is obtained from an open-circuit ratio, which is calculated based on the number of duty cycles per unit time counted by the duty cycle number counting means and the number of open-circuits per unit time counted by the open-circuit number counting means, and a relation of electric discharge and short-circuit ratios to the open-circuit ratio within unit time, and a frequency of electric discharge per unit time or distance is obtained based on the counted number of duty cycles per unit time and the obtained electric-discharge ratio.

4. The wire electric discharge machine according to claim 3, wherein the frequency of electric discharge and the number of short-circuits per unit time are obtained based on the electric-discharge ratio, the short-circuit ratio, and the number of duty cycles per unit time, whereby a machining amount per unit time or distance is obtained.

5. The wire electric discharge machine according to claim 3, wherein the open-circuit state identification means compares a full-wave-rectified machining-gap voltage waveform with a predetermined reference voltage within the quiescent time, identifies the open-circuit state if the reference voltage is exceeded, and identifies a closed-circuit state if the reference voltage is not reached, in contrast.