WIRE ELECTRICAL DISCHARGE MACHINING APPARATUS

• US 20140144885A1
• Filed: 07/06/2011
• Published: 05/29/2014
• Est. Priority Date: 07/06/2011
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Onodera, Yasuo, Nakagawa, Takayuki
• Granted Patent: US 9,308,594 B2
• Time in Patent Office: Days
• US Class Current: 219/69.12
• CPC Class Codes: B23H 7/10 Supporting, winding or electrical connection of wire-electrode
• CPC Class Codes: B23H 7/104 Wire tension control
• CPC Class Codes: B23H 7/14 Electric circuits specially adapted therefor, e.g. power supply B23H3/02 takes precedence

Abstract

In order to detect a wire breakage as soon as possible, the wire electrical discharge machining apparatus includes a speed fluctuation compensator that generates a speed fluctuation suppression command that is a speed compensation value that suppresses fluctuation of the rotational speed of the tension motor on the basis of the rotational speed of the tension motor and a breakage detecting device that detects a breakage of the wire electrode on the basis of a comparison of a preset breakage detection threshold and a speed fluctuation suppression command output from the speed fluctuation compensator.

Claims

1. A wire electrical discharge machining apparatus comprising:

a collecting roller that collects a wire electrode;

a collecting motor that causes the wire electrode to travel at a predetermined speed by driving the collecting roller;

a tension roller that applies tension to the wire electrode between the tension roller and the collecting roller;

a tension motor that drives the tension roller;

a speed calculating unit that calculates a rotational speed of the tension motor;

a speed fluctuation compensating unit that generates a speed compensation value that suppresses fluctuation of a rotational speed of the tension motor on a basis of a rotational speed output from the speed calculating unit; and

a breakage detecting unit that detects a breakage of the wire electrode on a basis of a comparison of a preset breakage detection threshold and a speed compensation value output from the speed fluctuation compensating unit.

2. The wire electrical discharge machining apparatus according to claim 1, wherein the breakage detecting unit issues a notification indicating that the wire electrode has broken when a speed compensation value output from the speed fluctuation compensating unit is larger than the breakage detection threshold and does not issue a notification indicating that the wire electrode has broken when a speed compensation value output from the speed fluctuation compensating unit is smaller than the breakage detection threshold.

3. The wire electrical discharge machining apparatus according to claim 1, wherein the breakage detecting unit measures an elapsed time during which a speed compensation value output from the speed fluctuation compensating unit continuously exceeds the breakage detection threshold, issues a notification indicating that the wire electrode has broken when the measured elapsed time is larger than a preset first elapsed time threshold, and does not issue a notification indicating that the wire electrode has broken when the measured elapsed time is smaller than the first elapsed time threshold.

4. The wire electrical discharge machining apparatus according to claim 1, wherein the breakage detecting unit performs an averaging process on a speed compensation value output from the speed fluctuation compensating unit, issues a notification indicating that the wire electrode has broken when a speed compensation value after the averaging process is larger than the breakage detection threshold, and does not issue a notification indicating that the wire electrode has broken when a speed compensation value after the averaging process is smaller than the breakage detection threshold.

5. The wire electrical discharge machining apparatus according to claim 1, further comprising a slip detecting unit that measures an elapsed time during which a speed compensation value output from the speed fluctuation compensating unit continuously exceeds the breakage detection threshold and issues a notification indicating that slip of the wire electrode is detected when the speed compensation value becomes equal to or smaller than the breakage detection threshold without the measured elapsed time reaching a preset second elapsed time threshold.