Mechanism design and process control of micro-EDM for drilling deep hole of bellows

Drilling is a kind of processing technology with a large proportion in mechanical processing, especially the drilling of deep hole, which is facing great challenges due to the high-strength properties of materials and debris-removal challenges. Because there is no obvious cutting force in the machining process and all conductive materials can be machined, microelectrical discharge machining (EDM) is playing an important role in deep hole drilling. In this study, micro-EDM technology was used for deep hole drilling on flexible bellows. Key technologies were discussed including workpiece positioning device, process control methods and drilling parameters selection. A special clamp was designed to solve the deformation problem of bellows positioning. In order to improve the consistency of the inlet and outlet of the deep hole, a double-sided guiding device was designed to reduce the radial deflection of tool electrode caused by the high spindle speed and long suspended stretch. The tool electrode compensation method was studied to improve the precision and aspect ratio of the deep hole. In addition, the influence of parameters such as spindle speed and oil flushing pressure on the drilling process was also analyzed. The study results show that the designed devices and process can meet the drilling requirements of the deep hole on bellows; the aspect ratio of the deep hole reaches 44:1.