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Zhongning Guo,Shunzhi Qiao,Liangliang Wang,Kai Zhang,Yingjie Xiao,Zhixiang Zou 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11
The electrochemical discharge machining (ECDM) is an advanced machining technology used to fabricate micro-holes in glass. In this study, a sheet tool electrode is employed to increase electrolyte circulation in machining zone. The effect of pulse voltage, frequency, duty cycle, electrolyte concentration, and tool rotation speed on the geometric properties of micro-holes were evaluated. The results showed that when using a sheet tool electrode, the machining depth increased by 42.9 %, and the machining efficiency increased by 51.1 %, while the entrance diameter was reduced by 13.9 % than cylindrical tool electrode. Additionally, the heat-affected zone (HAZ) and entrance hole surface quality is improved. On the other hand, the Taguchi method was employed to analyze the relative importance of the machining parameters on geometric characteristics of micro-holes (i.e. drilled depth and entrance diameter of micro-holes). Finally, the entrance hole overcut of 148 μm was successfully fabricated with a depth of 2520 μm. It was discovered that using a sheet tool electrode is a simple method for machining a deep micro-hole with high machining efficiency and a range entrance hole diameter overcut that is acceptable.
Junfeng He,Zhongning Guo,Haishan Lian,Junjie Wang,Xiaolei Chen,Jiangwen Liu 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.1
Traditional micromilling leaves burrs and has a high surface roughness in the workpiece, which compromises the microstructural machining quality. Electrophoresis-assisted ultrasonic micromilling machining (EUMM) is proposed to solve this problem. An electrophoresis assisted electric field is applied to attract abrasive particles into the machining gap. Combined with the ultrasonic vibrations of the workpiece, the impact and grinding effect of these abrasive particles in the machining gap removes burrs that are generated during machining and reduces the surface roughness of the microstructure. Micro channels were generated for this study to verify the proposed method. The experimental results show that the EUMM significantly reduces burr formation during microchannel milling. The EUMM also decreases the surface roughness (Ra); the bottom roughness using the EUMM (0.33 µm) is lower than that with either the ultrasonic micromilling (UMM) or traditional micromilling. The EUMM also improves the sidewall roughness since the grinding and particle impacts significantly smooth the sidewalls. The particles during EUMM ensure a low surface roughness of 0.34 µm for the vertical sidewalls. Furthermore, the EUMM has a lesser effect on the width of the micro channels; as the spindle speed increases, the microchannel width only increases from 486 to 498 µm.
Ting Huang,Zhongning Guo,Guiming Liang,Shunzhi Qiao,Pengcheng Cai,Zhixiang Zou 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8
The mask jet electrochemical deposition was used to deposit the large-scale micro cylinders array in this study. The effect of the pulse peak current density, pulse frequency, pulse duty cycle, injection pressure and scanning speed on the deposition characteristics (i.e. deposition height, surface roughness and surface quality of micro cylinders) have been investigated. The experiment results showed that the mean height and the surface roughness of micro cylinders increased form the peak current density. Moreover, due to a high pulse frequency provided a shorter pulse on-time, and significantly facilitating the renewal of the ion concentration in the electroforming fluid. A higher pulse frequency and larger duty cycle provide a better deposition characteristic. The injection pressure was found to have a significant effect on the height, the surface roughness and surface appearance of micro cylinders. Furthermore, when using higher scanning speed, the crystalline particles of the cast layer decrease, significantly decreasing the surface roughness. Based on discussed, the pulse current density of 12 A/dm 2 , a pulse frequency of 3000 Hz, a pulse duty cycle of 30 %, a jet inlet pressure of 80 kPa, a scanning speed of 8 mm/s and a number of scans of 100 is optimal parameters. Finally, by using these parameters, a large-area micro cylindrical array structures with a height of 22.53±2.46 μm and diameter of 205±3.21 μm were successfully fabricated. It can be concluded that the mask jet electrochemical deposition is a simple method to realize the electrodeposition of large-area array structures.
Zhixiang Zou,Xiaoyu Zhang,Kangcheung Chan,Tai-Man Yue,Zhongning Guo,Can Weng,Jiangwen Liu 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.6
Micro-electrical discharge machining (micro-EDM) has an issue of uneven tool electrode wear that seriously affects the micro-hole accuracy. However, the mechanism of uneven tool electrode wear remains unclear. In this study, the uneven tool electrode wear mechanism has been studied both theoretically and experimentally. It was first discovered that the ultrafine debris particles produced by the EDM spark play a critical role in uneven tool electrode wear. A theoretical model was established to reveal the movement and the distribution of the debris by employing Einstein’s tea leaf paradox i.e., classic secondary flow theory and the electrophoretic theory. According to this model, when the polarity is positive, the ultrafine debris aggregates gradually and adheres onto the bottom of the micro-hole, thereby a debris layer of a parabolic profile is formed progressively. This dynamic debris layer shields the material to be removed by the EDM spark. As a result, the tip of the tool electrode is unevenly worn into a conical concavity shape. Conversely, under negative polarity, the tip of the tool electrode is unevenly worn into a conical shape. A set of experiments was performed to verify the model and the results agreed well with the predicted phenomena. Subsequently, a novel approach is proposed to eliminate the uneven tool electrode wear by reversing pulse polarity in a repetitive manner. Using this method, uneven tool electrode wear can be avoided and high accuracy micro-holes without the features of a cone and/or conical concavity can be obtained.