Wire electrical discharge machine and control method

Patent metadata

Field	Value
Publication number	US-11666978-B2
Application number	US-202017011107-A
Country	US
Kind code	B2
Filing date	Sep 3, 2020
Priority date	Sep 9, 2019
Publication date	Jun 6, 2023
Grant date	Jun 6, 2023

Abstract

A wire electrical discharge machine includes: a voltage application unit for repeatedly applying a voltage to an electrode gap between the workpiece and the wire electrode at a predetermined cycle; a switching element connected in parallel with the electrode gap and configured to short-circuit the electrode gap; and a control section for controlling the switching element so as to short-circuit the electrode gap in a pause period during which the voltage is not applied. The control section adjusts a short-circuiting period in which the electrode gap is short-circuited according to the machining shape specified by a machining program.

First claim

What is claimed is:

1. A wire electrical discharge machine for performing electrical discharge machining on a workpiece using a wire electrode, comprising:
a voltage supply configured to repeatedly apply a voltage to an electrode gap between the workpiece and the wire electrode at a predetermined cycle;
a switch connected in parallel with the electrode gap and configured to short-circuit the electrode gap; and
a controller configured to control the switch so as to short-circuit the electrode gap in a pause period during which the voltage is not applied,
wherein the controller is configured to adjust a short-circuiting period in which the electrode gap is short-circuited according to a machining shape specified by a machining program stored in a non-transitory computer readable medium.

2. The wire electrical discharge machine according to claim 1 , wherein the controller is configured to lengthen the short-circuiting period in a case that the machining shape is an outer corner, compared to the short-circuiting period in a case that the machining shape is a straight line.

3. The wire electrical discharge machine according to claim 1 , wherein the controller is configured to shorten the short-circuiting period in a case that the machining shape is an inner corner, compared to the short-circuiting period in a case that the machining shape is a straight line.

4. The wire electrical discharge machine according to claim 1 , wherein the controller is configured to adjust the short-circuiting period according to a curvature of the machining shape.

5. The wire electrical discharge machine according to claim 1 , further comprising a voltage sensor configured to detect the voltage across the electrode gap,
wherein the controller is configured to set a target value of an average voltage applied per unit time to the electrode gap according to the machining shape, and adjust the short-circuiting period so that the average voltage measured using the voltage sensor becomes equal to the target value.

6. The wire electrical discharge machine according to claim 1 , further comprising a voltage sensor configured to detect the voltage across the electrode gap,
wherein the controller is configured to set the short-circuit period according to the machining shape, and adjust the set short-circuiting period so that an average voltage per unit time measured using the voltage sensor becomes equal to a target value.

7. The wire electrical discharge machine according to claim 1 , wherein the controller is configured to control the switch so as to short-circuit the electrode gap in all the pause periods that occur over time.

8. The wire electrical discharge machine according to claim 1 , further comprising a relative movement controller configured to relatively move the wire electrode relative to the workpiece,
wherein the relative movement controller is configured to determine a relative movement speed at which the wire electrode is moved relative to the workpiece, according to a ratio of total of first time lengths to total of second time lengths regarding the multiple voltages which are applied at the predetermined cycle in a unit time, the first time length means a time length from an application start time point of the voltage to a time point when electrical discharge occurs or a time point when the switch is turned on, whichever comes first, and the second time length means a time length from the application start time point of the voltage to the time point when the switch is turned on.

9. The wire electrical discharge machine according to claim 1 , wherein the controller is configured to adjust a short-circuiting period in which the electrode gap is short-circuited according to the machining shape comprising a type of shape recognized from the machining program.

10. The wire electrical discharge machine according to claim 1 , further comprising a discharge resistor connected in series with the switch and the wire electrode.

11. The wire electrical discharge machine according to claim 1 , wherein the controller is configured to analyze the machining program to determine the machining shape and control the switch to short-circuit the electrode gap in the short-circuit period.

12. The wire electrical discharge machine according to claim 11 , wherein the short circuit period is within the pause period during which the voltage is not applied.

13. A wire electrical discharge machine for performing electrical discharge machining on a workpiece using a wire electrode, comprising:
a voltage supply configured to repeatedly apply a voltage to an electrode gap between the workpiece and the wire electrode at a predetermined cycle;
a switch connected in parallel with the electrode gap and configured to short-circuit the electrode gap;
a voltage sensor configured to detect the voltage applied to the electrode gap; and
a controller configured to control the switch so as to short-circuit the electrode gap in a pause period during which the voltage is not applied,
wherein the controller is configured to adjust a short-circuiting period in which the electrode gap is short-circuited according to an average voltage per unit time measured using the voltage sensor.

14. The wire electrical discharge machine according to claim 13 , wherein the controller is configured to adjust the short-circuiting period so that the average voltage becomes equal to a target value.

15. A control method of a wire electrical discharge machine for performing electrical discharge machining on a workpiece using a wire electrode, comprising:
a voltage application step of repeatedly applying a voltage to an electrode gap between the workpiece and the wire electrode at a predetermined cycle; and,
a control step of controlling a switch connected in parallel with the electrode gap, so as to short-circuit the electrode gap in a pause period during which the voltage is not applied,
wherein the control step adjusts a short-circuiting period in which the electrode gap is short-circuited according to a machining shape specified by a machining program stored in a non-transitory computer readable medium.

16. The control method according to claim 15 , wherein the control step includes adjusting the short-circuiting period in which the electrode gap is short-circuited according to the machining shape comprising a type of shape recognized from the machining program.

17. The control method according to claim 15 , wherein the control step of controlling the switch connected in parallel with the electrode gap to short-circuit the electrode gap in a short-circuiting period and discharge electric charge accumulated in the electrode gap according to a discharge resistor connected in series with the switch and the wire electrode.

18. The control method according to claim 17 , wherein the short circuit period is within a pause period during which the voltage is not applied, and
wherein the control step includes analyzing the machining program to determine the machining shape and control the switch to short-circuit the electrode gap in the short-circuit period.

19. A control method of a wire electrical discharge machine for performing electrical discharge machining on a workpiece using a wire electrode, comprising:
a voltage application step of repeatedly applying a voltage to an electrode gap between the workpiece and the wire electrode at a predetermined cycle; and,
a control step of controlling a switch connected in parallel with the electrode gap, so as to short-circuit the electrode gap in a pause period during wh

Assignees

• Fanuc Corp

Inventors

• Furuta Tomoyuki
• Nakashima Yasuo

Classifications

• B23H2600/10

  Switching of machining conditions during machining · CPC title

• B23H1/024 Primary

  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 title

• B23H7/04

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

• B23H11/00

  Auxiliary apparatus or details, not otherwise provided for · CPC title

• B23H7/20

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