A novel discharging status distinguish method on machining Si ₃N₄ by HS-WEDM

Advanced engineering ceramics are more widely employed in modern industries for their excellent mechanical properties such as high hardness, high compressive strength, high chemical and abrasive resistance. Assisting electrode method makes ceramics machined successful in WEDM. Many experiments have been down by Hs-WEDM (high speed wire electrical discharge machining) under kerosene. In the machining, carbon will be cracked from the kerosene under high temperature and stuck to the positive pole in the voltage field. Characters of conductivity layer are also studied in this paper. Discharging voltage is changed at any moment, thus a simulation circuit is proposed to study the surface resistor in insulated ceramics machining. A resistor is used to act the conductivity layer in common material machining, and meanwhile, its resistor value would be changed to imitate the environment of ceramics machining by Hs- WEDM. Compared the result of simulation circuit with the real ceramics machining, this paper proposed that the discharging status should be divided in five types: short, open and three special discharging status under different maintaining voltage. By this means, conductivity layer resistor value can be got approximate and each discharging status can be got one correspondent control strategy. A novel detecting circuit is designed to distinguish the discharging status in this paper and experiments are done to test it.