WIRE ELECTRIC DISCHARGE MACHINE CAPABLE OF STARTING MACHINING FROM SHORT-CIRCUIT STATE

• US 20160045966A1
• Filed: 08/11/2015
• Published: 02/18/2016
• Est. Priority Date: 08/12/2014
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: HASEGAWA, Yasuo
• Granted Patent: US 10,144,076 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 1/026 Power supply protection, e.g. detection of power switch breakdown
• CPC Class Codes: B23H 7/02 Wire-cutting
• CPC Class Codes: B23H 7/04 Apparatus for supplying current to working gap; Electric circuits specially adapted therefor

Abstract

Even if a machining gap between a wire electrode and workpiece is in a short-circuit state at a start of machining by a wire electric discharge machine, a high-frequency voltage in a pulse shape is applied and a small current is supplied to an extent that the wire electrode is not fused only in an initial fixed time at the start of machining. Then, the short circuit is released, though instantaneously, and a discharge occurs in that instant and the short circuit state is eliminated by discharge repulsion thereof and therefore, machining can be started.

Claims

1. A wire electric discharge machine comprising:

a discharge inducing circuit including a first DC power supply connected to a machining gap between a wire electrode and workpiece via a first switching element and a current limiting resistance;

a current supply circuit including a second DC power supply connected to the machining gap via a second switching element;

a voltage detection circuit that detects a voltage of the machining gap;

a short-circuit detection unit that detects a short-circuit state between the wire electrode and the workpiece based on the voltage detected by the voltage detection circuit; and

a control circuit that controls on and off of the first switching element and the second switching element, wherein

the control circuit is configured to supply a predetermined discharge current to an extent that the wire electrode is not fused even in a short-circuit state with the workpiece until a predetermined state is reached after starting machining.

4. The wire electric discharge machine according to claim 1, wherein the wire electric discharge machine is configured to change to preset machining conditions when the short-circuit detection unit detects elimination of the short circuit between the wire electrode and the workpiece.

5. The wire electric discharge machine according to claim 4, wherein the wire electric discharge machine is configured to perform machining based on a machining program after changing to the preset machining conditions.

6. The wire electric discharge machine according to claim 1, wherein the wire electric discharge machine is configured to change at least one of a wire tension of the wire electrode, a flow rate of a working fluid, and a wire feed speed of the wire electrode until the short circuit is eliminated when the short circuit between the wire electrode and the workpiece is not eliminated before the predetermined state is reached.

7. The wire electric discharge machine according to claim 1, wherein the predetermined state is at least one of a preset time, a preset distance, and a preset number of times of discharge.

8. The wire electric discharge machine according to claim 1, wherein a discharge current to the extent that the wire electrode is not fused even in the short-circuit state of the wire electrode and the workpiece is determined by an experiment while each of a diameter, a material and a type of the wire electrode, a material and thickness of the workpiece to be machined, a specific resistance of a working fluid, and a wire tension needed to cause the wire electrode to travel is set.

2. A wire electric discharge machine comprising:

a discharge inducing circuit including a first DC power supply connected to a machining gap between a wire electrode and workpiece via a first switching element and a current limiting resistance;

a current supply circuit including a second DC power supply connected to the machining gap via a second switching element;

a voltage detection circuit that detects a voltage of the machining gap;

a short-circuit detection unit that detects a short-circuit state between the wire electrode and the workpiece based on the voltage detected by the voltage detection circuit; and

a control circuit that controls on and off of the first switching element and the second switching element, wherein

the control circuit is configured to supply a predetermined discharge current to an extent that the wire electrode is not fused even in a short-circuit state with the workpiece until a predetermined state is reached when the short circuit is detected by the short-circuit detection unit at a start of machining.

3. A wire electric discharge machine comprising:

a discharge inducing circuit including a first DC power supply connected to a machining gap between a wire electrode and workpiece via a first switching element and a current limiting resistance;

a current supply circuit including a second DC power supply connected to the machining gap via a second switching element;

a voltage detection circuit that detects a voltage of the machining gap;

a short-circuit detection unit that detects a short-circuit state between the wire electrode and the workpiece based on the voltage detected by the voltage detection circuit; and

a control circuit that controls on and off of the first switching element and the second switching element, wherein

the control circuit is configured to supply a predetermined discharge current to an extent that the wire electrode is not fused even in a short-circuit state with the workpiece until a predetermined state is reached after the wire electrode and the workpiece reach an open state by a pulse voltage being applied to the machining gap when the short circuit is detected by the short-circuit detection unit at a start of machining.