Wang Chenxue, Sasaki Tomohiro, Hirao Atsutoshi
Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
Faculty of Engineering, Niigata University, Niigata 950-2181, Japan.
Materials (Basel). 2023 Oct 13;16(20):6676. doi: 10.3390/ma16206676.
Accumulation and concentration of debris in deep hole electrical discharge machining (EDM) significantly hinder its machining efficiency and accuracy. It is believed that the movement of bubbles associated with the discharge gap flow field play a pivotal role in debris removal and influence the discharge conditions. Ultrasonic vibration (USV) of the electrode is thought to be an effective method for improving EDM-generated bubbles and debris exclusion. In this study, we first elucidated the behavior of bubbles during EDM of holes with varying aspect ratios. Subsequently, USV was introduced to EDM. The behavior of dielectric fluid flow under the influence of ultrasonic vibration was analyzed using computational fluid dynamics (CFD), which revealed time-varying changes in discharge gap flow pressure and velocity. The velocity of the dielectric flow field near the electrode's side face was found to reach a maximum of approximately 15.2 m/s, greatly facilitating debris removal. High-speed camera observations revealed that bubbles were dispersed within the side gap, with most of them adhering to the electrode's wall. Furthermore, the bubbles exhibited a tendency to continuously break up and coalesce near the hole's outlet before escaping in the USV-assisted EDM. These observed characteristics of bubble behavior under the influence of USV are expected to significantly enhance debris removal and promote efficient dielectric exchange.
深孔电火花加工（EDM）中碎屑的堆积和聚集严重阻碍了其加工效率和精度。据信，与放电间隙流场相关的气泡运动在碎屑去除中起着关键作用，并影响放电条件。电极的超声振动（USV）被认为是改善电火花加工产生的气泡和碎屑排出的有效方法。在本研究中，我们首先阐明了不同纵横比的孔在电火花加工过程中气泡的行为。随后，将超声振动引入电火花加工。使用计算流体动力学（CFD）分析了超声振动影响下的电介质流体流动行为，结果显示放电间隙流压力和速度随时间变化。发现电极侧面附近的电介质流场速度最高可达约15.2 m/s，极大地促进了碎屑的去除。高速摄像机观察表明，气泡分散在侧间隙内，其中大部分附着在电极壁上。此外，在超声振动辅助电火花加工中，气泡在孔口附近呈现出不断破碎和合并的趋势，然后逸出。预计在超声振动影响下观察到的这些气泡行为特征将显著提高碎屑去除率，并促进有效的电介质交换。
