Improvement of surface finish and accuracy utilising multi-step pulse waveforms in electrochemical micromachining.

To improve the localization of material dissolution and fabrication of microstructures with better surface finish, high process complexity, such as different tool shapes, electrolyte flow, and tool insulation, has been utilised in electrochemical micromachining (EMM). Improvement of mass transport, sludge removal, and continuous dissolution are challenging tasks for EMM because bubbles and sludge increase the shielding effects. To solve the problems and achieve precision machining with a better surface finish, a new multi-step pulse waveform (MSPW) is designed indigenously. By incorporating three different peak voltages with a short duration time in the pulse on time of MSPW, potential fluctuation is intentionally induced during machining. Thus, more pulse fall times, short peak voltage duration times, and fluctuations of potential can improve the reduction of bubble size and its detachment rate. Due to it, ion transport phenomena improve, sludge is properly removed from the machining zone, and material dissolution rates increase. The effects of MSPW in EMM are compared with conventional rectangular pulse waveform (RPW). From mathematical estimation, it is found that the power transmission of MSPW is less than RPW, which plays a significant role in stray current minimization. The proposed method is verified by simulation, where it can be observed that current density decreases with increasing bubble size. By capturing images, it is also noticed that the size of gas bubbles decreases, accompanied by a higher detachment rate. Utilising MSPW, precise microdimples are fabricated with minimum surface roughness (Ra), i.e., 0.0241µm, whereas Ra is 0.251µm for RPW. Further, it is identified from the machined microdimples that etch factor improves, diameter minimises, depth increases, no irregular machining appears on the bottom surface, and surface finish also improves as compared to RPW. These improvements are also observed in machined microholes. [ABSTRACT FROM AUTHOR]