Development of Ultra-high-precision Micromachining System using Dry EDM

本研究旨在发展一种利用干式电火花加工之超高精密微细加工系统。在干式电火花加工中，借助通过薄壁管电极提供的高压气流，可以将熔化的工件材料从工作间隙中清除并冲出，而不会重新附着在电极表面上。这种技术的最大优点之一是，工具电极磨损率几乎为零的任何脉冲持续时间。此外，与使用油作为电介质液体的常规EDM相比，工艺反作用力小得可以忽略，并且在加工表面上产生的残余应力非常低。因此，干式电火花加工有望成为最有前途的微细加工技术之一，然而，由于连续脉冲放电过程中短路的可能性高达95%，材料去除率远低于常规电火花加工。 关于我们 非常窄的工作间隙。因此，为了降低短路的可能性，首先在工作台上安装高频响应压电致动器，并由伺服控制器驱动，该伺服控制器与EDM机床的Z轴的原始伺服进给机构一起操作。第二，提高开路电压以获得更长的间隙距离以防止短路。实验结果表明，这两种措施都是有效的，以获得在材料去除率急剧增加，以缩小规模，可以实现使用干式电火花加工，应取消使用的管电极，因为有一个限制的最小直径的管电极。因此，通过从位于差距外部的喷嘴向放电间隙供应氧气射流来尝试使用固体电极的干式EDM。在氧气中通过WEDG加工的棒的最小直径为5 μ m，并且所获得的直径为15 μ m、长度为200 μ m的棒的变形比在电介质液体中获得的变形小得多。此外，工具电极的磨损率在干式微细电火花被发现是显着较低的，与传统的微细电火花在液体中相比。少

This research aims to develop an ultra-high-precision micromachining system using dry electrical discharge machining (dry EDM). In dry EDM, with the help of a high-pressure gas flow supplied through a thin-walled pipe electrode, the molten workpiece material can be removed and flushed out of the working gap without being reattached to the electrode surfaces. One of the greatest advantages of this technique is that the tool electrode wear ratio is almost zero for any pulse duration. Furthermore, the process reaction force is negligibly small and the residual stress generated on the surface machined is quite low compared with the conventional EDM using oil as the dielectric liquid. As a result, the dry EDM is expected to be one of the most promising techniques for micromachining.However, the material removal rate is considerably lower than that of the conventional EDM, because the probability of short circuiting during successive pulse discharge ranges up to ninety five percent due to th … More e extremely narrow working gap. Hence, to lower the probability of short circuiting, first a high frequency response piezoelectric actuator was installed on the working table and driven by a servo control which operates together with the original servo-feed mechanism of the Z-axis of the EDM machine. Secondly, the open voltage was raised to obtain a longer gap distance to prevent short circuiting. Experimental results show that both measures are effective to obtain a dramatic increase in the material removal rate.To scale down the size which can be achieved using the dry EDM, usage of the pipe electrode should be eliminated, because there is a limitation in the minimum diameter of the pipe electrode. Hence, the dry EDM using solid electrode was tried by means of supplying oxygen gas jet to the discharge gap from a nozzle which is positioned outside the gap. The minimum diameter of rods machined by WEDG in oxygen gas was 5 mu m, and the distortion of the obtained rod 15 mu m in diameter and 200 mu m in length was much smaller than that obtained in a dielectric liquid. Furthermore, the ratio of tool electrode wear in the dry-micro-EDM was found to be significantly low compared with that obtained with the conventional micro-EDM in liquid. Less