Micro-EDM of micro-stepped hole in YG8 cemented carbide by using micro milling cutter

Micro-stepped holes have been widely used in the fields of micro motor, precision mold, medical device, and so on. YG8 cemented carbide is widely used for machining micro-stepped hole because of its high hardness and good wear resistance. However, it is difficult to realize high-quality machining of micro-stepped holes on YG8 cemented carbide by turning and milling. Micro-EDM has no macroscopic cutting force and is not limited by material hardness, so it is the mainstream technology for machining microstructures on superhard materials. To address the above problems, the paper proposed to adopt micro-EDM to process the micro-stepped hole by using a micro milling cutter. Firstly, micro-EDM was carried out on YG8 cemented carbide with a high-speed rotating micro milling cutter to obtain the basic micro-hole structure. In the process of micro-EDM, the length of micro milling cutter was reduced due to wear. Secondly, micro-EDM was performed on the YG8 cemented carbide using the micro milling cutter with wear in length as the tool electrode, which was made to shake around the central axis of the basic micro-hole, so that a secondary basic micro-hole was machined on the basic micro-hole and a micro-stepped hole was formed. In the process of machining the secondary basic micro-hole, micro milling cutter with no wear would produce a secondary basic micro-hole with the same depth as the basic micro-hole, and no micro-stepped hole would be formed. In this paper, the wear of micro milling cutter in the length direction was transformed into a favorable factor. With the micro milling cutter shaking, a micro-stepped hole was obtained using the same micro milling cutter in different stages of EDM. Through a large number of machining experiments, the main process parameters were optimized and the experimental results were analyzed in this paper. Finally, the micro-EDM of YG8 cemented carbide was carried out with a micro milling cutter with a diameter of 400 µm at 2000 RPM rotational speed n , 90 V machining voltage V , and 0.5 duty ratio R , and a micro-stepped hole with good quality was obtained.