Accuracy improvement of micro-shafts fabricated by the twin-mirroring-wire tangential feed electrical discharge grinding

Abstract The new method of micro-shaft fabrication, named twin-mirroring-wire tangential feed electrical discharge grinding (TMTF-WEDG), is mainly characterized by the tangential feed strategy and the narrow slit formed by twin-mirroring-wire to achieve the diameter control of micro-shaft. The critical factors of micro-shafts accuracy and repeatability include processing position offset of micro-shaft, front edge position fluctuation of wire electrodes, and asymmetry of the twin-mirroring-wire electrodes, which cause the deviation of the tangential feed path and fluctuation in narrow slit width. The diameter of the micro-shaft was smaller than the theoretical value with processing position offset, which is not conducive to the control of the micro-shaft diameter. The front edge fluctuation of the wire electrodes caused the variation of the micro-shaft diameter to be around ±3 μm in the axial direction. The asymmetry of the twin-mirroring-wire electrode is the key factor affecting the tangential feed path which further affects the controlling the repeatability of the micro-shafts. New strategies were proposed, including the determination of the initial machining position achieved by tool setting, improvement of the twin-mirroring-wire system, the determination of the feed path, and improvement of feed strategy for trimming the taper of micro-shafts. The processing results show that a micro-shaft with a diameter of 45 μm and uniformity of ± 0.5 μm was successfully fabricated. For five repeated fabricated micro-shafts, the diameter repeatability was controlled within ±1 μm.