Electric heating – Metal heating – Cutting or disintegrating
Patent
1989-08-14
1991-08-13
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
B23H 710
Patent
active
050398342
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for wire tension control and disconnection detection for a wire-cut electric discharge machine.
2. Description of the Related Art
In a conventional wire-cut electric discharge machine, tension is applied to a running wire electrode (hereinafter referred to as the wire) by subjecting the wire to a braking force by means of a brake gear. The braking force is open-loop-controlled to adjust the wire tension to a predetermined value, and flexure of the wire caused by disconnection is detected by means of a limit switch opposed to the wire, thereby effecting disconnection detection.
According to the electric discharge machine with the construction described above, the braking force is controlled in an open-loop manner, so that the wire tension control sometimes cannot be accurately performed. Since a wire tension control system and a disconnection detection system are arranged independent of each other, moreover, high cost is entailed.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus for wire tension control and disconnection detection for a wire-cut electric discharge machine, the apparatus being capable of accurate wire tension control and disconnection detection and entails only low cost.
In order to achieve the above object, according to the present invention, there is provided an apparatus for wire tension control and disconnection detection for use in wire-cut electric discharge machine including a guide roller for guding a wire and a brake gear for applying a braking force to the wire, thereby producing a wire tension. This apparatus includes a lever supporting the guide roller for rotation and swingable support, tension detecting means for outputting a signal indicative of a load bearing on the lever through the guide roller and corresponding to the wire tension, brake control means for controlling the braking force in accordance with a difference between a value of the output signal of the tension detecting means and a set value of wire tension, and disconnection detecting means for detecting disconnection on the basis of the output signal of the tension detecting means.
According to the present invention, as described above, feedback control of the wire tension and the disconnection detection are effected in accordance with the output signal of the tension detecting means, which is indicative of the wire tension, so that the wire tension control and the disconnection detection can be accurately achieved, and a common sensor can be used for both the control and the detection, thus ensuring reduction in cost.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic view showing the principal part of a wire-cut electric discharge machine provided with an apparatus for wrie tension control and disconnection detection according to one embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODMENTS
In the accompanying drawing, a wire-cut electric discharge machine causes wire transportation means WT to drive a wire 1 delivered from a wire supply bobbin 3, thereby running the wire along a pinch roller 4, a brake roller 5, a guide roller 8, an upper guide 10, a machining groove formed on a workpiece 2, a lower guide 11, and a guide roller 12, and applies a machining voltage between the wire 1 and the workpiece 2, thereby causing electric discharge between them to effect electric discharge machining. Numberal 6 denotes an electromagnetic brake gear, which is arranged so as to brake the brake roller 5 to apply a braking force to the wire 1, thereby producing a wire tension. Numeral 17 denotes a backup plate for preventing the wire 1 from slipping off the guide roller 8 in case of, for example, disconnection.
Further, the electric discharge machine includes an apparatus for wire tension control and disconnection detection, which is provided with a of lever 7. One end of the lever 7 is pivotally supported by a shaft 7a, while the other end supports
REFERENCES:
patent: 4242556 (1980-12-01), Ullmann et al.
patent: 4298782 (1981-11-01), Wavre
patent: 4530471 (1985-07-01), Inoue
Izumiya Syunzo
Obara Haruiki
Evans Geoffrey S.
Fanuc Ltd.
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