Study of the effects of important factors on the diameter accuracy of micro-shafts fabricated by TMTF-WEDG

Abstract

It is very significant to improve the diameter accuracy of micro-shafts fabricated by micro-electrical discharge machining (micro-EDM) in micro-tools application. The diameter accuracy includes the uniformity of a single micro-shaft in axial direction and the repeatability of micro-shafts with the same diameter. A newly proposed method, named twin-mirroring-wire tangential feed electrical discharge grinding (TMTF-WEDG), can realize high uniformity and repeatability of micro-shafts via tangentially feeding and constraining of a narrow slit formed by a twin-mirroring-wire on the diameter of micro-shafts, respectively. Controlling the material removal thickness in single-step machining of micro-shafts is necessary to achieve high uniformity and repeatability. This paper focuses on the effects of the several important factors on the material removal thickness of micro-shafts to reveal the effects on the diameter uniformity and repeatability, including the open voltage, capacitance, feed rate in the Z-direction, feed step in the Y-direction, and tangential feed distance. The results indicate that the lower open voltage or the smaller capacitance or higher Z-direction feed rate, the smaller the thickness of the material removed, which is advantageous for controlling the consistency and repeatability of the micro-shafts. Decreasing of Y-direction feed step from 20 to 5 μm is accompanied by a reduction in material removal thickness, and the material removal thickness of less than 0.4 μm is achieved with a smaller feed step of in the Y-direction. As the tangential feed distance S2 decreases, the material removal thickness of the micro-shafts decreases gradually. In this study, the uniformity and repeatability of brass and tungsten micro-shafts are controlled within 1 μm and 2 μm, respectively.