Experimental Study Of Powder Mixed Edm And Its Mirror Processing Technology

PMD-EDM is attracting great attention in electrical machining field because of the important role in manufacturing of precise moulds & parts and hardening of part surface.In recent years, great progresses have been made in the research on it. It is known that the mix of powders widens discharge gap, disperses discharge points evenly, stabilizes discharge process, reduces SR, hardens surface material and increases MRR. However, little explication about the mentioned phenomena and the discharge principle has been given fully.This paper focuses on the following subjects: (1) the applied range of high MRR with PMD-EDM and its mechanism (2) how to combine finishing with mirror finishing reasonably and optimize discharge parameters to acquire the best surface within the shortest time in PMD (3) the reasons for reduction of the SR, the effect of the mixed powders during discharging and its influence on the electrostatic capacitance, the main form and change of the discharge channel during discharging in PMD.Some results are obtained from a series experiments. With a lower peak current, the MRR in PMD-EDM is higher than that in kerosene dielectric, however, with a higher one, the status is reversed. Under the same condition, the MRR in PMD-EDM increases firstly, and then decreases. The crater diameter by PMD-EDM is larger than that by conventional EDM, but the former SR is lower. MRR hardly varies along with the machining area when the electrical parameters are fixed.Finally, some viewpoints are presented as follows: The single channel form is dominant during discharging in PMD and dilation of channel in PMD is wider than that in kerosene dielectric. Furthermore, after adding powders into dielectric, it leads to anti-breakdown capacity reducing, gap widening, discharge point distributing evenly, and discharge stabilizing, so that the effect of electrostatic capacitance on PMD-EDM is lowered.The conclusions are helpful to guide application and will be the experimental base for constructing expert system of PMD-EDM, and the work also accelerates research on PMD-EDM mechanism.