Reducing overcut in electrochemical micromachining process by altering the energy of voltage pulse using sinusoidal and triangular waveform

Abstract

In electrochemical micromachining (ECMM), improved material dissolution localization and generation of the smooth machined surface under pulsed voltage condition is attributed to the fact that short pulse-duration time results in the generation of relatively less volume of dissolution products. The intermittent supply of voltage provides idle time to flush the hydrogen bubbles and sludge from the machining zone and, also increases control over the dissolution process. From the last few decades, various studies have been carried out to analyze the effect of short pulse voltage to ultra-short pulsed (rectangular) voltage. Development of such a sophisticated system capable of supplying ultra-high frequency voltage pulses is challenging, cost in-effective and complex. Also, the compromising ways of reducing the pulse energy by reducing the duty cycle and increasing the pulse frequency impose increased voltage requirement and idle time while machining. In this study, an approach of reducing pulse energy per unit time by changing the waveform of the voltage pulse (while keeping the pulse-duration time the same) for reducing the overcut is presented. A theoretical model is developed first to quantify the input energy per pulse for rectangular, sinusoidal, and triangular voltage pulses. This ensured that by changing the shape of voltage pulses of same on-time, the energy input per pulse can be further altered. A function generator based pulsed power supply is then developed with the capability of generating rectified voltage pulses of different waveforms. The process of ECMM for generating micro dimples on a flat surface is modeled in two dimensions using finite element method in MATLAB (R2018b). Three numerical models for sinusoidal, rectangular and triangular voltage pulses are developed for predicting the current density and anode shape. Simulation results demonstrated that triangular voltage pulse yields minimum diameter of micro-dimple as compared to sinusoidal and rectangular pulse respectively. Results from the developed model are also validated using experimental observations and a good correlation between the two was observed (with an average deviation of 18%).