The debris and bubbles accumulation cause the abnormal discharge increase, which limited the feed depth during drilling the micro hole with EDM. It was confirmed that most of the debris adhere to the negative polarity from the direct observation. However, apart from the phenomenon of adhesion to the negative electrode, the other characteristics of the debris are little known. In this paper, the characteristics of the adhesion are investigated by switching the tool polarity, which is helpful to better study and analyze the reasons why the debris are difficult to exhaust from inter-electrode area during drilling deep micro-hole by EDM.

It is well known that the movement of electrical discharge-generated gas bubbles plays a crucial role in debris exclusion, especially in the EDM (Electrical Discharge Machining) process of the micro-hole with the high aspect ratio. Applying ultrasonic vibration to EDM machining is thought to be an effective method to restrain debris accumulation and enhance bubble removal. In this paper, the effect of the ultrasonic vibration of the tool on the bubble behavior in EDM is investigated using a high-speed camera. The computational simulation of bubble behavior is studied by employing the VOF (Volume of Fluid) method with the proposed two-dimensional model of the flow field with liquid, and gas phases for the discharge gap. Bubble observation results show that machining debris scatters in the bubble's boundary and utilization of ultrasonic vibration of the tool will significantly improve the expansion bubbles exclusion in the discharge gap. It is also found from the numerical study that more vibration cycles will be necessarily needed for the bubble discharge from the gap outlet as the machining depth increases. Main Cause suggested for bubbles moving toward the gap outlet may be the periodic oscillation induced by the ultrasonic vibration. Furthermore, as demonstrated by the simulation results, the bubbles move along the edge of the electrode surface in the dielectric fluid.

SiC is a popular topic since it has better performance than conventional semi-conductor in electronic applications. However, the hardness of SiC approaches to that of diamond which results in a challenge for conventional electrical discharge machining (EDM). Compared to the conventional methods, EDM has different performances on SiC machining which should be investigated carefully. In this case, the LC pulse generator is used to machine SiC under different discharge energy. Gap phenomenon of SiC generated by LC pulse generator is observed by high speed video camera to get debris particles and damage layers of SiC which will be shown in this paper.

Precision ECM in stationary electrolyte using stamp flushing method has been proposed in our previous study to avoid the non-uniform distribution of temperature and bubbles caused by the high-speed flow of electrolyte during ECM. However, the radial flow field generated by the stamp flushing motion is axi-symmetrical, thus the fluid velocity in the center is slowest, limiting the removal efficiency of bubbles and sludge. This phenomenon deteriorates machining accuracy Here, the tool stroke motion was optimized to achieve high-precision machining. Results showed that the bubbles and sludge at the center of the gap can be effectively removed by using an optimized tool stroke motion. A smooth surface with a flatness of 5 μm was machined in this study.

Electrochemical machining (ECM) is a special machining method that has significant advantages in machining difficult-to-machine materials, complex shapes, or thin-walled parts. However, because the workpiece needs to contact the flowing electrolyte during machining, it is difficult to limit the machining area. In this study, based on the original experimental device and the ink supplying principle of the ballpoint pen, we developed a new vertical pressing processing equipment, which can effectively limit the processing area and observe the processing status intuitively.