Parametric investigation of pulse frequency and microtool rotational speed for precise fabrication of microchannels on nitinol shape memory alloy through ECMM

Abstract

Nitinol, a material with a unique combination of properties like shape memory effect, superelasticity, and biocompatibility, has become popular in the biomedical and micro-electro-mechanical systems (MEMS) industries. Electrochemical micromachining (ECMM) has emerged as an excellent method for micromachining Nitinol shape memory alloy (SMA) due to its ability to provide superior surface integrity and absence of any thermal effect. This study aimed at improving the surface integrity and the accuracy of the microfeatures on Nitinol fabricated through the ECMM process. The effects of process parameters like pulse frequency and microtool’s rotational speed on the diametral overcut of the microfeature were investigated at different inter-electrode gaps. The findings revealed that at 1 MHz pulse frequency and 500 rpm microtool rotating speed, the diametral overcut ranged from 0.163 µm at interelectrode gap (IEG) of 5 µm to 1.626 µm at IEG of 1 µm, indicating a precise microfeature fabrication. At the same parametric combination, the machined depth varied from 2.89 µm at IEG of 5 µm to 5.56 µm at IEG of 1 µm, suggesting a proportionate change in depth of the microfeature. Moreover, precise microchannels with average surface roughness values of 17.5 nm, 9.5 nm, and 12.4 nm were fabricated on the Nitinol surface at pulse frequencies of 1 MHz, 2 MHz, and 3 MHz, respectively.