Wire electric discharge machine including average discharge delay time calculating unit

Patent metadata

Field	Value
Publication number	US-10792744-B2
Application number	US-201715723160-A
Country	US
Kind code	B2
Filing date	Oct 2, 2017
Priority date	Jul 24, 2013
Publication date	Oct 6, 2020
Grant date	Oct 6, 2020

Abstract

In a wire electric discharge machine, time from application of a voltage to a machining gap between a workpiece and a wire electrode until occurrence of electric discharge is measured as a discharge delay time, and the measured discharge delay time is integrated over a predetermined measurement period to calculate a discharge delay integrated time. Further, the number of times of the voltage application in the measurement period is counted. An average discharge delay time per voltage application in the measurement period is calculated from the discharge delay integrated time and the number of times of voltage application. The movement of the wire electrode with respect to the workpiece is controlled on the basis of the average discharge delay time.

First claim

The invention claimed is:

1. A wire electric discharge machine that applies, while moving a relative position of a table with respect to a wire electrode, a voltage to a machining gap between the wire electrode and a workpiece arranged on the table to generate electric discharge and machines the workpiece, the wire electric discharge machine comprising:
a measurement circuit configured to measure, as a discharge delay time, a no-load time from the application of the voltage to the machining gap until occurrence of the electric discharge, and integrate the measured discharge delay time over a predetermined measurement period to calculate a discharge delay integrated time;
a counting circuit configured to count the number of times of the voltage application in the predetermined measurement period; and
a controller configured to calculate an average discharge delay time per voltage application in the predetermined measurement period from the discharge delay integrated time calculated by the measurement circuit and the number of times of voltage application calculated by the counting circuit, wherein, when the average discharge delay time is smaller than a predetermined reference value, the voltage application is not performed on the machining gap for a predetermined time.

2. The wire electric discharge machine according to claim 1 , wherein a relative position between the workpiece and the wire electrode is controlled such that the average discharge delay time coincides with a target value set in advance.

3. The wire electric discharge machine according to claim 1 , wherein
the measurement circuit comprises a machining gap average voltage measuring unit configured to calculate a machining gap average voltage by full-wave rectifying and averaging a voltage waveform of the machining gap, or averaging a voltage waveform that is half-wave rectified for each of polarities to calculate an average voltage for each of the polarities, and adding up average voltages, wherein
using the machining gap average voltage obtained by the machining gap average voltage measuring unit, machining gap average voltage fixed servo feed control is executed.

4. The wire electric discharge machine according to claim 1 , wherein
the controller comprises a state signal output unit configured to discriminate a voltage waveform applied to the machining gap as any one state of opening, electric discharge, and short circuit, and output a state signal; and
the counting circuit comprises a state counting unit configured to count at least two or more of the number of times of opening, the number of times of electric discharge, and the number of times of short circuit in the measurement period by counting the state signal output from the state signal output unit every time a voltage is applied to the machining gap, wherein
servo feed control is performed by obtaining a servo feed speed by using at least one of the number of times of opening, the number of times of electric discharge, and the number of times of short circuit obtained by the state counting unit.

5. The wire electric discharge machine according to claim 1 , wherein the wire electric discharge machine calculates, with the measurement circuit and the counting circuit, the discharge delay integrated time in the predetermined measurement period and the number of times of the voltage application for both or any one of polarities in each of a case in which a machining gap voltage is positive and a case in which the machining gap voltage is negative, and
the wire electric discharge machine calculates, with the controller, the average discharge delay time corresponding to the polarity in each predetermined measurement period.

6. The wire electric discharge machine according to claim 1 , wherein the discharge delay integrated time is an integrated value of time in which a waveform obtained by full-wave rectifying a machining gap voltage in the predetermined measurement period or a waveform obtained by half-wave rectifying any one of a positive voltage and a negative voltage is equal to or larger than a predetermined reference voltage value.

7. The wire electric discharge machine according to claim 1 , wherein the discharge delay integrated time is an integrated value of time from a point when a waveform obtained by fullwave rectifying a machining gap voltage in the predetermined measurement period or a waveform obtained by half-wave rectifying any one of a positive voltage and a negative voltage is equal to or larger than a predetermined first reference voltage value to a point when the waveform is equal to or smaller than a predetermined second reference voltage value.

Assignees

• Fanuc Corp

Inventors

• Furuta Tomoyuki

Classifications

• B23H1/022 Primary

  for shaping the discharge pulse train (B23H1/024 takes precedence) · CPC title

• B23H7/04

  Apparatus for supplying current to working gap; Electric circuits specially adapted therefor · CPC title

• B23H7/20

  for program control, e.g. adaptive · CPC title

• B23H7/18 Primary

  for maintaining or controlling the desired spacing between electrode and workpiece · CPC title