Study on trepanning variable-parameter electrochemical discharge machining of tungsten microneedles

Tungsten microneedles have broad application prospects. However, the high hardness and high melting point of tungsten make it difficult for conventional methods to simultaneously achieve high forming efficiency, dimensional accuracy, and surface quality. To address this issue, a two-stage variable-parameter study on trepanning electrochemical discharge machining of tungsten microneedles was carried out. Through constant-parameter experiments, the effects of peak current and pulse width on machining performance and surface morphology were analyzed, and the critical values of peak current and pulse width were determined to be approximately 9 A and 9 μs, respectively. On this basis, a two-stage variable-parameter machining scheme with strong parameters in the first stage and weak parameters in the second stage was established. The results show that the two-stage variable-parameter machining strategy can significantly improve the overall diameter-reduction efficiency of tungsten microneedles and enhance tip convergence. Among all the tested parameter combinations, the combination of 18 A and 24 μs in the first stage and 8 A and 6 μs in the second stage showed the best performance, with a material removal rate of 638.82 μg/s, an electrode wear rate of 73.21 μg/s, a tip diameter of 24.78 μm and a surface roughness of 0.72 μm. Therefore, the two-stage variable-parameter trepanning electrochemical discharge machining strategy can achieve high machining efficiency, good surface quality, and a tiny tip diameter, providing an effective solution for the fabrication of tungsten microneedles.