Study On The Mechanism And Application Of Powder-mixed EDM

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.For this reason, the mechanism and processing performances of powder-mixed EDM are studied by means of theoretical analysis combined with experimental research in this dissertation to improve the technology.Firstly, by means of the streamer theory from gas discharging field, the gap breakdown procedure of powder-mixed EDM is discussed, and the shape of the discharge channel is subsequently deduced. It is believed that the discharge channel connects the electrode couple via some certain particle and series-discharging is then conducted. And the single-channel discharge model is accepted rather than the multi channel discharge model according to the analyzed results. The bettering of the machined surface roughness is accounted for the over expansion of the plasma channel radius at the anode which causes a decrease in the local energy density at the anode surface. In addition, because the particles eliminates the dependence of the new discharge position on the last discharge position, the discharge point can be uniformly dispersed all over the machining area, which also accounts for the improvement of the machined surface integrity.Secondly, in order to meet various needs for different powder material, the service performances of silicon powder and aluminium powder are studied. It is found that compared to silicon powder, if a higher concentration of aluminium powder is set, the same degree of surface roughness and a higher MRR can be achieved. With the aluminium powder concentration changed, the effect of powder concentration on the process performance is also researched, and keeping the powder concentration within a proper range is found important to both the machined surface roughness and MRR.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.