METHOD OF CUTTING OUT PART WITH MAKING PARTIALLY WELDED SPOTS IN WIRE-CUT ELECTRICAL DISCHARGE MACHINING

• US 20120193326A1
• Filed: 12/14/2011
• Published: 08/02/2012
• Est. Priority Date: 01/28/2011
• Status: Active Grant

• Current Assignee: Seibu Electric & Machinery Co., Ltd.
• Original Assignee: Seibu Electric & Machinery Co., Ltd.
• Inventors: MITSUYASU, Takashi
• Granted Patent: US 8,476,548 B2
• Time in Patent Office: Days
• US Class Current: 219/69.17
• CPC Class Codes: B23H 7/04 Apparatus for supplying current to working gap; Electric circuits specially adapted therefor
• CPC Class Codes: B23H 7/06 Control of the travel curve of the relative movement between electrode and workpiece
• CPC Class Codes: B23K 9/007 Spot arc welding

Abstract

A method of cutting out a part from a workpiece with making partially welded spots in wire electrical discharge machining to keep the part against falling apart away from the workpiece. There is no need to cut anew the welded spot left as in the conventional process. The cut-out parts are cut off at a time after breakage of the welded spots caused by an external impact. The electric processing condition applied across an inter-electrode space between the wire electrode and the workpiece is changed from a cutting phase to a welding phase in which the wire electrode is fused partially at some spots along a cutting path of a predetermined contour on the workpiece to weld together the cut-out part and the workpiece at the fused spot on the wire electrode.

Claims

1. A method of cutting out a part with making partially welded spots in wire electrical discharge machining in which a wire electrode unwound from a source bobbin is threaded through a workpiece lying below an upper head and further a lower head lying below the workpiece in opposition to the upper head, and then the wire electrode is fed through a guide member lying downstream of the lower head towards a waste-wire hopper;

comprising the steps of, changing electrical processing condition applied across the wire electrode and the workpiece from a cutting phase to a welding phase at more than one spot in a cutting path or kerf of a predetermined contour on the workpiece to fuse partially the wire electrode at the spot, and welding together the workpiece and the part cut out from the workpiece at the spot with using the fused wire electrode, thereby keeping the cut-out part at the spot against falling away apart from the workpiece.

2. A method of cutting out a part with making partially welded spots in wire electrical discharge machining, as set forth in claim 1, wherein an electric current fed through the wire electrode to weld together the cut-out part and the workpiece at the spot is applied with a long pulse less at a peak current amount compared with an electric current in the cutting phase to carry out the wire electrical discharge machining whereby the machining discharge shifts to an arc discharge to fuse the wire electrode to weld together the workpiece and the cut-out part with using the fused wire electrode.

3. A method of cutting out a part with making partially welded spots in wire electrical discharge machining, as set forth in claim 1, wherein the electrical processing condition is controlled to cut the workpiece while making coalescence between the workplace and the cut-out part at the spot where workpiece and the cut-out part are opposite to each other.

4. A method of cutting out a part with making partially welded spots in wire electrical discharge machining, as set forth in claim 1, wherein the coalescence after discharge machining has been completed is broken with an external impact to cut off the cut-out part away from the workpiece.

5. A method of cutting out a part with making partially welded spots in wire electrical discharge machining, as set forth in claim 1, wherein changing the electrical processing condition is carried out with an electric circuitry which has a first circuit in which an inter-electrode space between the wire electrode and the workpiece is connected in series with a low-voltage load combined with a resistance to confirm an inter-electrode state and a 1st switch, a second circuit in which the space between the wire electrode and the workpiece is connected in series with a high-voltage load for the electric discharge machining and a 2nd switch, and a third circuit in which the space between the wire electrode and the workpiece is connected in series with a 1st diode and a 3rd switch, and the first, second and third circuits being connected in parallel with each other, whereby phase-change from the cutting phase to the welding phase is executed by ON•

OFF control of the switches.

6. A method of cutting out a part with making partially welded spots in wire electrical discharge machining, as set forth in claim 5, wherein the cutting phase on the workpiece is executed by the steps of turning on the 1st switch to energize the low-voltage load to apply a potential difference across the inter-electrode space between the wire electrode and the workpiece, and then turning off the 1st switch and turning on the 2nd switch to energize the high-voltage load thereby executing the cutting phase on the workpiece.

7. A method of cutting out a part with making partially welded spots in wire electrical discharge machining, as set forth in claim 5, wherein the welding phase on the workpiece is executed by the steps of turning on the 1st switch and the 3rd switch to energize the low-voltage load to apply a potential difference across the inter-electrode space between the wire electrode and the workpiece, then, keeping the 3rd switch turned on while turning off the 1st switch and turning on the 2nd switch to energize the high-voltage, and finally turning off the 2nd switch while keeping the 3rd switch turned on to release energization of the high-voltage load to apply a circulating current across the inter-electrode space between the workpiece and the wire electrode to generate an electric current long in pulse width, thereby making the coalescence between the cut-out part and the workpiece.

8. A method of cutting out a part with making partally welded spots in wire electrical discharge machining, as set forth in claim 1, wherein changing the electrical processing condition is carried out with an electric circuitry which is composed of a first circuit in which an inter-electrode space between the electrode and the workpiece is connected in series with a low-voltage load combined with a resistance to confirm an inter-electrode state and a 1st switch, a second circuit in which the inter-electrode space between the wire electrode and the workpiece is connected in series with a high-voltage load for the electric discharge cutting, a 4th switch and a 5th switch, a third circuit in which the inter-electrode space between the wire electrode and the workpiece is connected in series with a 2nd diode and a 5th switch, and a fourth circuit in which a inter-electrode space between the wire electrode and the workpiece is connected in series with a 3rd diode and a 4th switch, and the first, second, third and fourth circuits being connected in parallel with each other, whereby the phase-change from the cutting phase to the welding phase is executed by ON•

OFF control of the switches.

9. A method of cutting out a part with making partially welded spots in wire electrical discharge machining, as set forth in claim 8, wherein the cutting phase is executed by the steps of the cutting phase on the workpiece is executed by the steps of turning on the 1st switch to energize the low-voltage load to apply a potential difference across the inter-electrode space between the wire electrode and the workpiece, then turning off the 1st switch and turning on the 4th switch and the 5th switch to energize the high-voltage load thereby executing the cutting phase on the workpiece.

10. A method of cutting out a part with making partially welded spots in wire electrical discharge machining, as set forth in claim 8, wherein the welding phase on the workpiece is executed by the steps of turning on the 1st switch to energize the low-voltage load to apply a potential difference across the inter-electrode space between the wire electrode and the workpiece, then turning on the 4th switch and the 5th switch while turning off the 1st switch to energize the high-voltage, and then keeping the 4th switch and the 5th switch turned on to keep energization of the high-voltage, and finally turning off the 4th switch while keeping the 5th switch tuned on to release energization of the high-voltage load to apply a circulating current across the inter-electrode space between the workpiece and the wire electrode to generate an electric current long in pulse width, thereby making the coalescence between the cut-out part and the workpiece.

11. A method of cutting out a part with making partially welded spots in wire electrical discharge machining, as set forth in claim 1, wherein the fused part in the wire electrode to weld together the cut-out part and the workpiece is limited to only a wire periphery of the wire electrode to make certain that the wire electrode is fed continuously without interruption even after the wire electrode has been partially fused to weld the cut-out part with the workpiece.

12. A method of cutting out a part with making partially welded spots in wire electrical discharge machining, as set forth claim 1, wherein upon breakage of the wire electrode at the partially fused part to weld the cut-out part with the workpiece, the wire electrode is newly resupplied into cutting path or kerf at a breakage spot to continue the welding phase or the cutting phase.