Identification of interelectrode gap sizes in pulse electrochemical machining

Pulse electrochemical machining offers significant improvements in dimensional accuracy as compared with conventional electrochemical machining. One primary issue in pulse electrochemical machining is to identify and control the interelectrode gap size. This paper presents an identification method for the gap size by in-process analysis of machining current pulses. Stochastic modeling and analysis of the current pulses reveal two gap indicators: pulse signal variance and damping ratio. The variance has a linear relationship with the gap size within a commonly used gap range of 0.10 to 0.20 mm for a wide range of pulse durations. The damping ratio has been found to be highly correlated with the gap size. Laboratory experiments confirm the feasibility of this method under unevenly distributed gap conditions. The process mechanism underlying these findings is also discussed.