Precision electrochemical machining of tungsten micro-rods using wire electrochemical turning method
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ORIGINAL ARTICLE
Precision electrochemical machining of tungsten micro-rods using wire electrochemical turning method Wei Han 1 & Masanori Kunieda 1 Received: 18 April 2020 / Accepted: 20 September 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract The novel wire electrochemical turning (WECT) method has been proposed to machine tungsten with neutral electrolyte and bipolar pulse current in the authors’ previous research. The influence of tool wear caused by the bipolar pulse current, which is needed to remove the oxide layer generated on tungsten surface when using a neutral electrolyte, was eliminated by the WECT method because the wire tool electrode was kept being wound during the machining process. In this paper, the influences of the most important process parameters, such as the kind of electrolyte, wire material, wire diameter, rotation speed of the workpiece rod, and frequency of the pulse voltage, were studied to understand the fundamental aspects of the WECT method and improve the machining efficiency of tungsten micro-rods. The experimental results showed that the NaCl electrolyte and the NaNO3 electrolyte had higher machining efficiency and better machining accuracy, respectively. The machining accuracy was improved with the SUS304 stainless steel wire used as tool electrode than the brass wire tool electrode. It was also found that the machining efficiency and accuracy were improved with decreasing the wire diameter and increasing the rotation speed of workpiece because the influence of stray current flowing through the side and end surface of machined micro-rod was reduced. The machinable length of micro-rod peaked at an optimum feed speed of the workpiece, and the optimum speed increased with increasing the frequency of pulse voltage. As a result, a minimum rod diameter of 11 μm was fabricated with a high aspect ratio of 36. Compared with the previous method using a platinum film as tool electrode, the aspect ratio was increased significantly because the influence of tool wear was eliminated. Keywords Wire electrochemical turning . Electrochemical machining . Tungsten . Micromachining . Electrostatic induction feeding method
1 Introduction Tungsten has a unique set of properties like the second highest melting point next to carbon among all elements, high elastic modulus, high density, high thermal conductivity, and excellent mechanical properties at elevated temperatures [1]. These exceptional properties make tungsten to be widely used in the fields of optics, micro-electronics, mechanical manufacturing,
* Wei Han [email protected] Masanori Kunieda [email protected] 1
Department of Precision Engineering, The University of Tokyo, Room 833, Engineering Building 14#, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
and aerospace [2]. In recent years, tungsten has also been used as promising alternative materials for plasma facing components in fusion reactors, owing to its high melting point and low sputtering yield [3]. However, tungsten has a major dr
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