BEHAVIOUR OF BUBBLES GENERATED IN ELECTRO-CHEMICAL DISCHARGE MACHINING

The present paper emphasized on the behavior of bubbles formed around the electrodes in Electro-Chemical Discharge Machining (ECDM) process as a factor of spark initiation. A finer observation on the voltage-current (V-I) characteristics prior to the discharge is made to investigate the bubble behavior. V-I characteristics are recorded and analyzed experimentally with different combinations of the electrolytes, tool diameter and tool depth. It has been clearly observed that there are three distinct regions in the V-I characteristics for alkaline, neutral and acidic electrolyte. Due to local turbulence at higher current density, the linear nature of V-Icharacteristic curve changes and decrease in cell resistance is noticed. However this local turbulence has little effect on critical voltage or critical current. The span of the region near to the spark onset is different for different electrolytes.