Multiphysics research on electrochemical machining of micro holes with internal features
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ORIGINAL ARTICLE
Multiphysics research on electrochemical machining of micro holes with internal features Guodong Liu 1,2 & Hao Tong 1,2 & Yong Li 1,2 & Hao Zhong 1,2 & Qifeng Tan 1,2 Received: 9 June 2020 / Accepted: 17 August 2020 / Published online: 24 August 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract Micro electrochemical machining (ECM) is practicable for machining micro holes with internal features by adjusting machining parameters along with machining depths. However, it is difficult to maintain the shape accuracy due to dramatically varied electrolyte temperature (T) and gas void fraction (vol) caused by the parameter variations. Taking the reverse tapered hole as an example, this research presents a multiphysics model to investigate the effects of machining parameters on T and vol and further optimize parameters for shape accuracy improvement. Firstly, the rules of current efficiency with various pulse-on times are measured from dissolution experiments. The gas fluxes are calculated from the Faraday current, and then multiphysics models coupling electric field, electrolyte flow, gas transport, and heat transfer are established by COMSOL software. The effects of the machining voltage, pulse-on time, duty ratio, and inlet pressure are investigated. Simulation results indicate that T and vol increase with the machining voltage or duty ratio and decrease with the inlet pressure. By using a smaller duty ratio or a higher inlet pressure, the sidewall dissolution region expands in a larger range. Increasing the inlet pressure is beneficial for reducing the negative influence of rising T and vol. However, excessive inlet pressure causes undesired material dissolution. The optimal inlet pressures are obtained from simulation results of the electrolyte vortex area. Micro ECM experiments are carried out to verify the simulation results and optimize the parameters. Micro reverse tapered holes with sidewall straightness of 8.6 μm are machined, and the shape accuracy is significantly improved. Keywords Micro ECM . Micro hole . Internal feature . Multiphysics model . Shape accuracy
1 Introduction Mechanical parts present a trend of miniaturization and precision with the demands for compact and multi-functional industrial products. Micro features such as micro holes, microgrooves, 3D structures, etc. are machined on mechanical parts to realize their functional requirements. Among them, micro holes with complex internal features are increasingly applied, such as reverse tapered holes, streamlined holes, and bambooshaped holes, which can achieve superior performances [1–3]. In addition to the dimensional and geometrical characteristics, * Yong Li [email protected] 1
Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipments and Control, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
2
State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
high aspect ratio and smooth surfaces are also required. In the case of no
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