Simulation of nano-second pulsed phenomena in electrochemical micromachining processes – Effects of the signal and double layer properties

Abstract

Pulsed electrochemical micromachining is a metal dissolution process where the capacitive behaviour of the double layer enhances the confinement of the machining profile, when very short voltage pulses are applied. During the pulses, the dissolution is confined to electrode regions where the tool–workpiece gap is the smallest. The model used combines the potential distribution in the electrolyte with the load–unload behaviour of the double layer. The model is solved using the Finite Element Method. The pulse and double layer charging are the main focus and therefore no shape change is included in the model at this point. The influence of the double layer, pulse signal parameters and inter-electrode gap size on the dissolution current density (material removal depth), as a function of time, is investigated. An estimation of the double layer loading time is presented, as well as a quantification method for the metal removal confinement, by comparing the calculated error against an ideal removal profile. The influence of pulse characteristics on the dissolution process has also been studied. It was found that a strongly non-linear polarization in combination with nano-second pulses and a small gap size increases the confinement. All the simulation results were obtained on an axisymmetric case by considering several geometrical set-ups.