Study of added powder in kerosene for the micro-slit machining of titanium alloy using electro-discharge machining

This work presents a revised EDM process by quantitatively and qualitatively measuring the process using different dielectric fluids, The revised EDM process is developed by modifying the discharging circuit to minimize the discharging current and introducing a new driven mechanism with horizontal rotating electrode. By applying a thin copper diskette electrode, titanium alloy is machined using micro-slit EDM with various dielectric fluids. The dielectric fluids used herein are kerosene, kerosene with aluminum powder, and kerosene with SiC powder. The effects of the various fluids used during the machining process are numerous. Such effects are more clearly accounted for by closely examining the material removal depth, the electrode wear rate, the slit expansion, the surface roughness, and the waveform of the discharging condition. The addition of both SiC and aluminum powder to the kerosene permit an extension of the gap between the electrode and the workpiece. The extended gap increases the debris removal rate and the material removal depth. Furthermore, a bridging effect is created by the added powder drifting within the kerosene and, in doing so, facilitates the dispersion of the discharge into several increments. Thus, several discharging trajectories are formed within a single input impulse and several discharging spots are created within a discharging impulse also. The effects due to the discrete discharging pulses are elucidated, these effects being the minimizing of the machined debris, which is easily removed, and the increasing of the material removal depth and surface roughness. However, the addition of the powder to the kerosene disturbs the adherence of carbon nuclides attached to the surface of the electrodes. By doing so, the electrode wear rate is increased, as also is the slit expansion. (C) 2000 Elsevier Science S.A. All rights reserved.