Electric discharge machine and electric discharge machining method

[0023]FIG. 1 is a block diagram showing an electrical wire discharge machine according to a first embodiment of the present invention. The electrical wire discharge machine proceeds with machining by applying a voltage between a workpiece 1 and a wire electrode 2 within a working tank 8; and causing an electrical discharge through a dielectric fluid squirted from an upper dielectric fluid nozzle 4 and a dielectric fluid squirted from a lower dielectric fluid nozzle 5, to thus fuse and eliminate the target areas of the workpiece 1.

[0024]At this time, an electrical discharge portion of the wire electrode 2 is also fused / deteriorated in accordance with a progress in electrical discharge operation. Accordingly, the wire electrode 2 wound around a wire bobbin 3 is continuously fed to a recovery box 7 through the upper dielectric fluid nozzle 4, the lower dielectric fluid nozzle 5, and a recovery roller 6 so that a new wire electrode 2 is fed to the machining section in association with a

[0061]In the present embodiment, the working tank 8 is imparted with the function of the anticorrosive electrode as shown in FIG. 5.

[0062]According to the configuration, the working tank 8 and the table 9 are insulated from each other by the mount 10. The dielectric fluid exists between the working tank 8 and the table 9. Hence, the insulator 24 becomes obviated. Further, the area of the electrode is wide, and hence the electrical resistance of the electrode is lowered, which in turn enables a reduction in voltage and current.

[0063]By the wire electrical discharge machine having the method for preventing corrosion of a workpiece, which would otherwise be caused by application of the voltage, the conductivity of the dielectric fluid was controlled to 6.2 μS / cm (corresponding to a pH value of 9.0). Further, a voltage of 3 volts was applied between the table 9 and the working tank 8. Thus, corrosion of a superhard material (WC-Co) or an iron-based material (SKD-11) was prevented during