The Processing Mechanism Of Electrical Discharge Machining Of Al₂O₃/Cu Composite Electrode

The gap of processing is very small in electrical discharge machining. The dielectric fluid is difficult flowing in processing gap. And the dielectric fluid flow slowly in around corner of the end gap and side of electrode. So the electric erosion particles deposited on around corner of the end gap, the residence time of backlash against electrode side is growing. The accumulation of particles will change the electric field in the interelectrode, rise the temperature in the interelectrode, make against to the ionization of interelectrode dielectric fluid and discharge point beating on the processing surface. It will happen arc discharge and burn the surface of the electrode. The accumulation of particles will also have the bypass effect in the electrode gap and it make two discharge, electrode tip blunt, lateral pits and pock, worse accuracy of tool electrode. Accordingly, the workpiece along the deep direction have machining angles and appear horn mouth. So the workpiece precision is droped. So in order to eliminate the influence of electric erosion particles on the tool electrode, made use of Al2O3material to protect the copper electrode matrix and reduce damage the copper electrode of the accumulation of electric erosion particles.Using the two electrode in the process of test, one is composite electrode, the other is common copper electrode. Mainly discusses the processing speed, electrode wear rate, hole taper and diameter expansion rate of process parameters under the same processing conditions. To study these parameters how changes in the difficult current and pulse width. In data contrast figures show that electrode wear rate, holes taper and diameter expansion rate of composite electrode is better than conventional copper electrode. This reflects the protective effect of composite materials on electrode. The high melting point and insulation of the coating material, reducing the discharge of two times of the electric erosion of particles action, improves the machining accuracy. But the processing speed of the composite electrode is less than the copper electrode, because the thickness of the coating problem. It should be improvement in the continue test.At the end of the article also proposed the use of composite processing circumferential magnetic field and electrical discharge machining. The magnetic field is mainly plays the role of the electron and positive ion in the discharge path. The main purpose is to change the direction of movement of electrons and ions, reduce the electrons free travel from cathode to anode and compression of the discharge channel under the action of the circumferential direction of magnetic field. So that increasing the discharge channel density, increasing the impact probability between electron and particles and increasing the new electronic production. Cathode material removal volume increases and improve processing speed by more electrons to the anode.