Method of Electro-Machining by Superposition of High Frequency Oscillations

Abstract

The machining of hard metals can easily be performed nowadays by the method of electro-machining, which was first introduced by Lazarenko and was developed by many engineers. The machining, however, can be done only when condenced discharges or quenched sparks are initiated between a metal plate to be machined and an electrode, which is in incomplete contacts or in repeated contacts to the plate. Further, to increase the accuracy of machining and the working speed the plate must be connected as the anode in a direct current circuit.
In the present method, the plate and the electrode, which are connected in an alternating current circuit, are separated to each other keeping a small gap, and are dipped into water. Applying high frequency oscillations between them in every other half cycles, at which the plate is in the positive potential, we can initiate quenched discharges only in the half cycles and are able to perform the electro-machining of the plate. Thus, with no use of the direct current source and repeated contacts of the electrode we can easily machine hard metals, especially tungsten plates, which are considered as being not easy to drill by both electro-mechanical and pure mechanical methods.
Peculiallity of the present method is that even minute cracks do not grow in the machined surface and that screw cutting can be done easily by a screw of an electrode which progress-es by a guidance of a screw of the same pitch. Time for drilling a tungsten plate 3mm in thickness by a tungsten rod 1.54mm in diameter is 4 minutes with discharge current about 1 Amp., and the diameter of a hole drilled is 1.75mm. In the last section mechanisms of the electro-mechanical machining due to quenched discharges are explained qualitatively; the drilling effect being ascribed to electric attraction action on the melt of the plate, and loss of the electrode to a bluster effect of positive ions.