電気加工学会誌

In this paper, a new method of electrochemical machining (ECM), where high-voltage pulses are intermittently supplied to electrodes during low-voltage pulsed ECM, is presented. The properties of this method are compared with those of a conventional low-voltage pulsed ECM method using a 0.3 mmφ electrode. We found that this method enables us to machine a workpiece using ECM conditions that are difficult to use in the conventional ECM method, such as low electrolyte concentration and low pulse duty ratio. This method also enable us to machine a workpiece without strong flushing. The machining speed of this method is increased almost 3-6 times that of the conventional ECM method. A small side gap width comparable to the gap width of EDM is achieved using a low-density NaNO₃ electrolyte.

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As a method of processing cemented carbide, wire electrical discharge machining (WEDM) is generally used. However, typical surface defects, such as cracks, microcraters and recast layer, lead to a decreased surface integrity, probably resulting in a short tool life. Therefore, it is desirable to eliminate these surface defects by some methods. Thus, an on-the-machine surface modification technology in WEDM, for the complete elimination of surface defects, was developed in this study. The surface defects are eliminated using a wire electrical discharge machine by introducing surface integrity cut (SI cut) after applying a large number of WEDM finishing cuts. SI cut is carried out as follows. Wires are passed through the same contour with a wire offset of 0μm in SI cut after the final finishing cut by WEDM. It can be considered that a recast layer including cracks is selectively eliminated by the dissolution of cobalt based on the electrolytic action during SI cut. As a result, the surface defects generated by WEDM could be completely eliminated by incorporating SI cut into WEDM. Thus, this surface modification technology is effective for finishing cemented carbide machined by WEDM.

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