Method of automatically recovering wire breakage in wire electric discharge machine

• US 5,753,880 A
• Filed: 01/10/1997
• Issued: 05/19/1998
• Est. Priority Date: 05/11/1995
• Status: Expired due to Fees

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Yoda, Shinji, Kajitori, Toyotada
• Primary Examiner(s): Evans, Geoffrey S.
• Application Number:
  US08/765,960
• Time in Patent Office: 494 Days
• Field of Search: 219/69.12, 364/474.04
• US Class Current: 219/69.12
• CPC Class Codes: B23H 7/102 Automatic wire threading

Abstract

A method of recovering a wire breakage in a wire electric discharge machine in which a wire is automatically connected through a machining groove near a wire breakage position to reduce a time from the wire breakage to the restarting of the electric discharge machining. After detecting the wire breakage, the wire is automatically connected at an intermediate position between the wire breakage position and a start point of a machining block in which the wire breakage occurred under the conditions that the machining block is of a straight-line command or of a circular-arc command having a radius larger than a set radius r0 and a length D between the wire breakage position and a start point of the machining block is equal to or larger than a set length D0. If the above conditions are not satisfied and if a machining block immediately preceding the machining block in which the wire breakage occurred satisfies the above conditions, the wire is automatically connected at an intermediate position between the start and end points of the immediately preceding machining block. If the immediately preceding machining block does not satisfy the above conditions, the wire is automatically connected at a position of a machining start hole.

Claims

1. A method of automatically recovering a wire breakage in a wire electric discharge machine having upper and lower guides disposed on a wire path, an annealing and fusing device for annealing and fusing the wire by an electric current flow in the wire from a pair of wire-fusing electrodes disposed upstream of the upper guide, and a nozzle for spouting a machining fluid to restrict a direction of the wire being fed from the upper guide, said method comprising the steps of:

(a) annealing a portion of the wire upstream of a position of the wire breakage and fusing an end of the annealed wire portion by said annealing and fusing device, and removing the portion of the wire exhausted by electric discharge machining and separated by the fusing, when the wire is broken during electric discharging machining;

(b) discriminating whether a machining block in which the wire breakage has occurred is of a straight-line command or of a circular-arc command;

(c) discriminating whether or not said machining block is of a circular-arc command having a radius equal to or larger than a set radius, if it is discriminated that said machining block is of a circular-arc command in said step (b);

(d) discriminating whether or not a length of movement of the wire on a machining path between a start point of the machining block and the wire breakage position is equal or larger than a set value, if it is discriminated that the machining block is of a straight-line command in said step (b) or of a circular-arc command having a radius equal or larger than the set radius in said step (c);

(e) automatically connecting the wire at an intermediate position on the machining path between the start point of said machining block and the wire breakage position while spouting the machining fluid from said nozzle to restrict the wire, if it is discriminated that the length of movement of the wire on the machining path between the start point of said machining block and the wire breakage position is equal to or larger than the set value in said step (d);

(f) discriminating whether a machining block immediately preceding said machining block is of a straight-line command or of a circular-arc command, if it is discriminated that said machining block in which the wire breakage occurred is of a circular-arc command having a radius smaller than the set value in said step (c) or if it is discriminated that the length of movement of the wire on the machining path between the start point of the machining block and the wire breakage position is smaller than the set value in said step (d);

(g) discriminating whether, or not said immediately preceding machining block is of a circular-arc command having a radius larger than the set radius if it is discriminated that said immediately preceding machining block is of a circular-arc command in said step (f);

(h) discriminating whether or not a length of movement of the wire on a machining path between start and end points of said immediately preceding machining block is equal to or larger than the set value, if it is discriminated that said immediately preceding machining block is of a straight-line command in said step (f) or if it is discriminated that the immediately preceding machining block is of a circular-arc command having a radius larger than the set radius in said step (g);

(i) automatically connecting the wire at an intermediate position on the machining path between the start and end points of said immediately preceding machining block while spouting the machining fluid from said nozzle to restrict the wire, if it is discriminated that the length of movement of the wire on the machining path between the start and end points of said immediately preceding machining block is equal to or larger than the set value in said step (h); and

(j) automatically connecting the wire at a position of a machining start hole, if it is discriminated that said immediately preceding machining block is of a circular-arc command having a radius smaller than the set radius in said (g) or if it is discriminated that the length of movement of the wire on the machining path between the start and end points of said immediately preceding machining block is smaller than the set value.

2. A method of automatically recovering a wire breakage according to claim 1, wherein said intermediate position of the machining block is set to be a central position on the machining path between the start point of the machining block and the wire breakage position in said step (e), and said intermediate position of the immediately preceding machining block is set to be a central position on the machining path between the start and end points of said immediately preceding machining block in said step (i).

3. A method of automatically recovering a wire breakage in a wire electric discharge machine having upper and lower guides disposed on a wire path, an annealing and fusing device for annealing and fusing the wire by an electric current flow in the wire from a pair of wire-fusing electrodes disposed upstream of the upper guide, and a nozzle for spouting a machining fluid to restrict a direction of the wire being fed from the upper guide, said method comprising the steps of:

(a) annealing a portion of the wire upstream of a position of the wire breakage and fusing an end of the annealed wire portion by said annealing and fusing device, and removing the portion of the wire exhausted by electric discharge machining and separated by the fusing, when the wire is broken during electric discharging machining;

(b) discriminating whether a machining block in which the wire breakage has occurred is of a straight-line command or of a circular-arc command;

(c) discriminating whether or not said machining block is of a circular-arc command having a radius equal to or larger than a set radius, if it is discriminated that said machining block is of a circular-arc command in said step (b);

(d) discriminating whether or not a length of movement of the wire on a machining path between a start point of said machining block and the wire breakage position is equator larger than a set value, if it is discriminated that the machining block is of a straight-line command in said step (b) or of a circular-arc command having a radius equal or larger than the set radius in said step (c);

(e) automatically connecting the wire at an intermediate position on the machining path between the start point of said machining block and the wire breakage position while spouting the machining fluid from said nozzle to restrict the wire, if it is discriminated that the length of movement of the wire on the machining path between the start point of said machining block and the wire breakage position is equal to or larger than the set value in said step (d);

(f) tracing back a machining program to find a machining block of a straight-line command or of a circular-arc command having a radius larger than the set radius and in which the distance between the start and end points of the machining block is larger than the set value, if it is discriminated that said machining block in which the wire breakage occurred is of a circular-arc command having a radius smaller than the set value in said step (c) or if it is discriminated that the length of movement of the wire on the machining path between the start point of the machining block and the wire breakage position is smaller than the set value in said step (d);

(g) automatically connecting the wire at an intermediate position on the machining path between the start and end points of said machining block found in said step (f) while spouting the machining fluid from said nozzle to restrict the wire; and

(h) automatically connecting the wire at a position of a machining start hole if there is not found any machining block of a straight-line command or of a circular-arc command having a radius larger than the set radius and in which the distance between the start and end points of the machining block is equal to or larger than the set value.

4. A method of automatically recovering a wire breakage according to claim 3, wherein said intermediate position of the machining block is set to be a central position on the machining path between the start point of the machining block and the wire breakage position in said step (e), and said intermediate position of the found machining block is set to be a central position on the machining path between the start and end points of said machining block in said step (g).