Electric heating – Metal heating – Cutting or disintegrating
Patent
1989-11-29
1991-05-28
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
B23H 702, B23H 710
Patent
active
050196847
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a wire disconnection position detecting apparatus in a wire-cut electric discharge machine.
Background Art
A typical wire-cut electric discharge machine is constructed so that electric discharge machining is stopped to effect wire connection automatically when wire disconnection is detected by means of a limit switch, which is disposed along a feed path for a wire electrode (hereinafter referred to as wire) and operates in response to reduction of wire tension or suspension of the travel of the wire caused by the wire disconnection, whereupon the electric discharge machining is restarted. Depending on the types of the causes of the wire disconnection, however, the wire may possibly snap again immediately after the restart of the electric discharge machining. In such a case, purposeless connection work is repeated, so that the machining efficiency is lowered, and a workpiece suffers streaky flaws on its surface with every disconnection of the wire. Thus, the quality of machined products is lowered.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a wire disconnection position detecting apparatus of a wire-cut electric discharge machine, capable of detecting and displaying a wire disconnection position in order to clear up the causes of wire disconnection.
In order to achieve the above object, a wire disconnection position detecting apparatus according to the present invention comprises means for detecting disconnection of a wire electrode; means for rewinding the snapped wire electrode in the direction opposite to the feeding direction of the wire electrode so that a cut end of the wire electrode passes a predetermined position on a wire electrode feed path; means for detecting the rewinding amount of the wire electrode; and means for displaying a wire disconnection position in accordance with the rewinding amount of the wire electrode thus detected.
According to the present invention, the wire disconnection position is displayed in accordance with the rewinding amount of the wire electrode rewound so that the cut end passes the predetermined position on the wire electrode feed path. Accordingly, the causes of the disconnection can be easily cleared up in accordance with the displayed information, so that purposeless repetition of wire connecting work can be avoided. Thus, the machining efficiency and the quality of machined products can be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view showing the principal part of a wire-cut electric discharge machine according to one embodiment of the present invention;
FIG. 2 is a block diagram showing a numerical control device of the electric discharge machine of FIG. 1; and
FIG. 3 is a flow chart showing a wire disconnection position detecting process executed by the control device of FIG. 2.
BEST MODE OF CARRYING OUT THE INVENTION
In FIG. 1, a wire-cut electric discharge machine is constructed so that a workpiece 201 placed on a table 19 is subjected to electric discharge machining as a winding motor M2 is rotated to feed a wire electrode (hereinafter referred to as wire) 200 wound on a supply reel 1 from the reel 1 along a predetermined wire feed path. More specifically, the wire 200 fed from the reel 1 is delivered to pulleys 4 and 4' through a roller 2 of a disconnection detecting apparatus and a brake roller 3 of a tension generating device opposed to the roller 2. Subsequently, the wire 200 is delivered to a lower pulley 11 through an upper feeder 5, an upper wire guide 6, an upper nozzle 7, the workpiece 201, a lower nozzle 8, a lower wire guide 9, and a lower feeder 10. Then, the wire 200 is held between a winding roller 12 operatively connected to the motor M2 and a pinch roller 13 opposed to the roller 12, and is driven by both these rollers 12 and 13 which rotate accompanying the rotation of the motor M2, so that the wire is cast in a wire recovery box 20. In the meantime, electric power is supplied to the wire 200 from the upper and lower fee
REFERENCES:
patent: 4116551 (1978-09-01), Kim et al.
patent: 4298781 (1981-11-01), Inoue
patent: 4412118 (1983-10-01), Nomura et al.
patent: 4414457 (1983-11-01), Nomura et al.
patent: 4689457 (1987-08-01), Izumiya et al.
Evans Geoffrey S.
Fanuc Ltd.
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