Real-time monitoring of process current and its correlation with micro-feature accuracy and surface topography in electrochemical micromachining of nitinol

Abstract

The nickel-titanium alloy known as Nitinol classified as a shape memory alloy is distinguished by its exceptional attributes, including shape memory effect, biocompatibility, and superelasticity. However, its thermo-mechanical dependent transformation behavior makes it difficult to process using traditional methods. Electrochemical micromachining (ECMM), a non-traditional fabrication method, uses anodic dissolution process to produce microfeatures on Nitinol. The current work emphasizes the impact of process current on the machining accuracy and surface topography of microchannels produced during ECMM of Nitinol utilizing ethylene glycol-based sodium nitrate electrolyte. The ECMM process parameters that were studied are pulsed potential, molar concentration, and micro-tool scan rate, and the development of the process current resulting in variation of these parameters during microchannel fabrication was closely observed. The statistical parameters, namely, the average process current and the process current fluctuation, were derived from the process current data that were further analyzed with respect to input parameters. The machining accuracy and the surface topography of the microchannel are analyzed by measuring the width overcut, channel depth, stray region, width standard deviation, and average surface roughness of the fabricated microchannel. The results showed that monitoring the process current in real-time is an effective way of controlling the process, particularly when it comes to fabricating micro-features that must adhere to strict predetermined criteria.