Electric heating – Metal heating – Cutting or disintegrating
Patent
1986-04-23
1987-11-17
Pellinen, A. D.
Electric heating
Metal heating
Cutting or disintegrating
219 69D, B23H 702, B23H 710
Patent
active
047075805
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. TECHNICAL FIELD
The present invention relates to a wire-cut electrical discharge machine and, more particularly, to a wire-cut electrical discharge machine equipped with an improved cooling system at least in the upper wire guide assembly of the wire guide unit, for cooling the feeder pin.
2. BACKGROUND ART
A wire-cut electrical discharge machine feeds an electrode in the form of an electroconductive wire, referred to as an electrode wire, wound on a feed reel through a tensioning brake drum, a guide roller, an upper guide assembly, a lower guide assembly, and a motor-driven winding roller, and winds the electrode wire onto a take-up reel, while an electric discharge voltage is applied through the feeder pins to the electrode wire across the upper and lower guide assemblies to discharge sparks between the electrode wire and a workpiece placed on an X-Y table for electrical discharge machining. The upper and lower wire guide assemblies are disposed above and below the X-Y table, respectively, and are provided with feeder pins, upper and lower guide heads for guiding the electrode wire along a straight line through the workpiece, and cooling liquid supply passages, respectively. During the electrical discharge machining operation, an electric current flows through the feeder pins and the workpiece. Although the intensity of the electric current is dependent on the machining conditions, normally, the intensity of the electric current is about 10A. Ordinarily, the electrode wire is a brass wire having a diameter in the range of 0.1 to 0.3 mm. Accordingly, a high Joulean heat is produced in the electrode wire when such an electric current flows through the electrode wire. In order to prevent objectionable overheating of the electrode wire due to the Joulean heat produced therein, a cooling liquid is supplied through the cooling liquid supply passage to a cooling nozzle formed so as to surround the electrode wire and the cooling liquid is spouted through the cooling nozzle against the working portion of the electrode wire running near the workpiece, to cool the electrode wire. Since not only the working portion of the electrode wire but also a portion of the same between the point of contact between the electrode wire and the feeder pin and the wire guide head needs to be cooled, part of the cooling liquid introduced into the cooling liquid supply passage is supplied through a narrow branch passage to the feeder pin to cool the feeder pin and a portion of the electrode wire in the vicinity of the feeder pin.
Recently, the electrical discharge machining speed has been increased and the enhancement of the cooling effect and the chip removing effect has been a significant subject of improvement. In a recent wire-cut electrical discharge machine, the cooling liquid is spouted at a comparatively high pressure, for example, at 5 atm. Accordingly, the cooling liquid is spouted at a high pressure also against the feeder pin, and thereby the cooling liquid is sprayed outside the wire-cut electrical discharge machine to contaminate the environment of the wire-cut electrical discharge machine, for example, to soil the adjacent machines with the spray of the cooling liquid.
When the diameter of the narrow branch passage for supplying the cooling liquid to the feeder pin is reduced further to suppress the increase of the pressure of the cooling liquid supplied to the feeder pin as a means of solving such a problem, the cooling liquid is insufficiently supplied to the feeder pin and, sometimes, the cooling liquid is not supplied at all to the feeder pin when the pressure of the cooling liquid, particularly, the pressure of the cooling liquid at the cooling nozzle, is reduced to the lowest possible extent to meet the operating conditions of the wire-cut electrical discharge machine. Accordingly, the wire-cut electrical discharge machine needs a feeder pin cooling system capable of controlling the flow rate of the cooling liquid supplied to the feeder pin according to the pressure of the cooling liquid introduce
REFERENCES:
patent: 4205212 (1980-05-01), Ullmann et al.
patent: 4250371 (1981-02-01), Haug et al.
patent: 4459454 (1984-07-01), Inoue
patent: 4460816 (1984-07-01), Bonga
patent: 4539459 (1985-09-01), Yamagata
Aso Toshiyuki
Kinoshita Hiroshi
Evans Geoffrey S.
Fanuc Ltd.
Pellinen A. D.
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