Monitoring and control of the micro wire-EDM process

A new pulse discriminating and control system has been developed for process monitoring and control in micro wire-EDM. The pulse discriminating and control system identifies four major gap states classified as open circuit, normal spark, arc discharge and short circuit based on the characteristics of gap voltage waveform. The effect of pulse interval, machining feedrate and workpiece thickness on the variations of the proportion of normal spark, arc discharge and short circuit in the total sparks (defined as normal ratio, arc ratio and short ratio, respectively) were investigated. It is found that a long pulse interval results in an increase of the short ratio under a constant feedrate machining condition. A high machining feedrate or an increase of workpiece height results in an increase of the short ratio. To achieve the stability of the machining operation, a control strategy is proposed by regulating the pulse interval of each spark in real-time according to the identified gap states. Experimental results indicate that the developed pulse discriminating and control system can significantly reduce the arc discharge and short sparking frequency as well as achieve stable machining under the condition where the instability of machining operation is prone to occur.