Variable-parameter high-precision electrochemical discharge drilling method for 440C-Nb without recast layer
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ORIGINAL ARTICLE
Variable-parameter high-precision electrochemical discharge drilling method for 440C-Nb without recast layer Jingyang Zhang 1 & Zhengyang Xu 1 & Chenxiang Zhang 1 Received: 25 March 2020 / Accepted: 5 August 2020 / Published online: 16 September 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract Engine nozzle orifices are broadly used in the automotive field, and their manufacture entails high drilling accuracy, consistency, and excellent machined surface quality. Electrochemical discharge drilling (ECDD) is an innovative compound machining technique, which can be used to machine small holes of difficult-to-cut materials. Electrical discharge machining (EDM) as well as electrochemical machining (ECM) can occur simultaneously in ECDD, owing to which it can obtain not only good surface quality but also high processing speed. However, the machining accuracy, taper, and surface quality achieved using ECDD do not satisfy the requirements of engine nozzle orifices, which are of a higher standard. For improving the machining accuracy and surface quality, a variable-parameter electrochemical discharge drilling (VPECDD) has been proposed. The machining process is divided into two consecutive stages, including perforation and shape modification, while different parameters are used in different stages. In this study, the finite element method was applied to study the mechanism of VPECDD, and comparative experiments were performed among EDM, ECDD, and VPECDD. The results indicate that VPECDD can achieve very high machining accuracy and consistency, obtain an inlet and outlet diameter difference at 0.002 mm, maintain an average hole taper at 0.0004°, and remove the recast layer completely. Finally, it is verified that VPECDD is suitable for machining microholes with high precision and no recast layer. Keywords Electrochemical discharge drilling (ECDD) . Variable parameter . Engine nozzle orifices . Stainless steel . Hybrid machining . Recast layer
1 Introduction As a fuel atomization device, an engine nozzle is a core component of an engine combustion chamber. The geometry accuracy of a nozzle hole will affect the atomization performance of a nozzle, and the bad atomization performance will result in ignition delay in the engine combustion process [1]. The inconsistency of nozzle orifice diameters will result in an
* Zhengyang Xu [email protected] Jingyang Zhang [email protected] Chenxiang Zhang [email protected] 1
National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
uneven distribution of fuel quality, which will deteriorate the combustion quality of the engine [2]. Unsmooth structures and high roughness on the inner wall of nozzle orifices will result in abnormal fuel flow rates and the inability of the jet flow to remain symmetric and stable [3]. The sharp inlets of nozzle orifices will result in low flow rates and uneven flow of the fuel with high turbulence level [4]. The
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