Breakthrough detection and servo control for micro‑hole array EDM drilling
Breakthrough detection and servo control for micro‑hole array EDM drilling
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DOI：
10.1007/s00170-021-08205-w
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发表时间：
2021-11
期刊：
影响因子：
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通讯作者：
Huan Liu;Jicheng Bai;Bo Zhang;Yan Cao;Shaojie Hou;Zimu Zhou
中科院分区：
文献类型：
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作者：
Huan Liu;Jicheng Bai;Bo Zhang;Yan Cao;Shaojie Hou;Zimu Zhou
微细电火花加工的微孔阵列在航空航天、电子通信等工业领域得到了广泛的应用。然而，由于电极突破过程中不可避免的电极磨损和放电状态不稳定，电极突破检测通常不准确，伺服跟踪性能也较差，对微孔阵列的加工效率和质量产生不利影响。本研究建立了三维流场模型，并基于该模型对电极突破前后的间隙流场进行了分析。仿真结果表明，电极突破工件后，介质流场格局发生了变化，底部间隙流速普遍增大，可以在一定程度上分析碎屑冲刷机理的变化对突破阶段放电状态的影响。提出了一种通过监测间隙电压和电极位移变化在线检测突破的方案，并进行了验证实验。实验表明，该方案在保证电极突破的同时，控制电极通过微孔出口的距离不超过25 μm。为保证微孔阵列的加工性能，提出了一种分段伺服策略，并进行了实验验证。该策略可使微孔阵列的平均加工时间缩短约36%，保证微孔出口的加工质量。
The micro-hole array machined by micro-electrical discharge machining (micro-EDM) has been widely used in aerospace, electronic communication, and other industrial fields. However, due to the unavoidable electrode wear and the unstable discharge state during the electrode breakthrough, the electrode breakthrough detection is usually inaccurate, and the servo tracking performance is also poor, which has adverse effect on the machining efficiency and quality of micro-hole array. In the present study, a three-dimensional flow field model was established, and the gap flow field before and after electrode breakthrough based on the model was analyzed. Simulation results showed that the flow field pattern of dielectric was changed and the flow velocities in bottom gap increased in general after electrode broke through the workpiece, which enabled to analyze the influence of the variation in flushing mechanism of debris on the discharge state in breakthrough stage to some extent. A scheme was proposed for online detecting the breakthrough by monitoring the variations of the gap voltage and the electrode displacement, and the verification experiment was carried out. The proposed scheme has been shown to guarantee the electrode breakthrough, while in the same time controlling the distance of electrode feeding past the micro-hole outlet not exceeding 25 μm. In addition, a segmented servo strategy was proposed to ensure the machining performance of micro-hole array, and it was experimentally tested. This strategy could reduce the average machining time of micro-hole array by about 36% and ensure the machining quality of micro-hole outlet.