Analysis of circuit current in electrochemical micromachining process under the application of different waveforms of pulsed voltage

Abstract

Selection of optimal pulsed voltage parameters such as waveform, pulse rise and fall time, frequency, and duty ratio is very important to achieve the desired machining efficiency and accuracy in electrochemical machining (ECM). At present, this selection is done by conducting time-consuming and costly trial experiments. It is well understood that the volume and rate of material dissolution in ECM is dependent on the current flowing between the two electrodes. However, only a part of this current, called as Faradaic current, is responsible for the anodic dissolution and the rest of it, called as capacitive current, is consumed in charging the electrical double layer (EDL) capacitance which forms at the interface. Therefore, it is vital to understand the variation of Faradaic current in the system to arrive at optimal pulse parameters. An increase in the current flowing between the two electrodes does not ensures an increase in the Faradaic component of that current. To the best of authors' knowledge, there does not exists any method or device, to date, which can break the system current into its components and provide their variation explicitly. This research attempts to fill in this gap by provide a method of breaking the overall system current into its constituents by investigating the system under consideration using electrochemical impedance spectroscopy (EIS). The results of EIS are used to virtually construct an equivalent electrical circuit in MATLAB® Simscape and the current is simulated for different waveforms of pulsed voltage input. To access the correctness of the trends of Faradaic current obtained through simulations, an experimental study is conducted. Both simulation and experimental study is conducted for three waveforms of pulsed voltage namely: half wave rectified rectangular (RVW), sinusoidal (SVW), and triangular (TVW). For experimentation, these waveforms are obtained with the help of a rectification-cum-amplification circuit which is designed and developed in lab. Further optimization of triangular waveform is performed by varying its rise and fall time in five different cases. It is finally concluded that the trends of Faradaic current obtained from simulation study are in good agreement with the experimental results.