Completion detection and efficiency improvement for breakout stage of fast EDM drilling
Completion detection and efficiency improvement for breakout stage of fast EDM drilling
复制标题
快速电火花钻孔突破阶段的完井检测及效率提升
DOI：
10.1007/s00170-021-06936-4
复制
发表时间：
2021-03-31
影响因子：
3.4
通讯作者：
Zhao, Wansheng
中科院分区：
文献类型：
--
作者：
Zhang, Yaou;Xia, Weiwen;Zhao, Wansheng
放电加工（EDM）是一种非传统的加工工艺，通过连续的电火花去除材料。快速电火花钻削加工就是其中之一，它采用旋转管状电极和内冲洗技术来提高加工效率和稳定性。广泛应用于各种产品的小孔加工。当电极在钻孔过程期间刚好穿透工件时发生断裂事件，这标志着过程的断裂阶段的开始。此时，孔的出口由于严重的径向刀具磨损而小于期望值，并且孔未完成。因此，在电极完全穿透工件之前需要进一步进给。为避免井眼回冲，完井检测至关重要。然而，纵向和径向刀具磨损的不确定性使其困难。本文提出了一种新的方法来检测孔完成通过分析放电信号在崩落阶段。此外，针对加工效率在开断阶段较低的问题，提出了通过调整伺服控制器的参考电压和增益因子来提高加工效率的控制策略。通过全因子实验确定了最佳工艺参数。通过在不同倾角下钻孔的实验，验证了所提出的方法。结果表明，所提出的成孔检测方法可以成功地感知成孔，而不会出现误判。并且当进行检测时，电极从孔出口最多送出1.81mm。此外，所提出的控制策略提高了加工效率高达56.2%，在漏钢阶段的实验。
Electrical discharge machining (EDM) is a non-conventional machining process that removes material by consecutive electrical sparks. Fast EDM drilling is one of such processes, which employs rotary tubular electrodes and inner flushing to enhance the machining efficiency and stability. It is widely used to produce small holes on various kinds of products. The breakout event occurs when the electrode just penetrates the workpiece during the drilling process, which marks the start of the breakout stage of the process. At this moment, the outlet of the hole is smaller than the desired due to severe radial tool wear, and the hole is not completed. As a result, further feeding is needed before the electrode fully penetrates the workpiece. To avoid back-strikes, the hole completion detection is crucial. However, the uncertainty of longitudinal and radial tool wear makes it difficult. This paper proposes a novel method to detect the hole completion by analyzing the discharge signals in the breakout stage. Besides, for the machining efficiency to become much lower in the breakout stage, the control strategy is also proposed to improve it by adjusting the reference voltage and gain factor of the servo controller. The optimal parameters were found by a full-factorial experiment. Experiments were conducted to validate the proposed methods by drilling holes at various inclinations. The results show that the proposed hole completion detection method could successfully sense the hole completion without misjudgments. And the electrode was fed at most 1.81 mm out of the hole outlet when the detection was made. Besides, the proposed control strategy improved the machining efficiency by up to 56.2% in the breakout stage in the experiments.