Papers by Keyword: Powder-Mixed EDM

Abstract: The powder mixed electro-discharge machining (PMEDM) technologies of silicon carbide particle reinforced aluminium matrix composites (SiCp/Al) are researched in this article. SiCp/Al is widely acknowledged as one of the most competitive varieties of metal matrix composites, firstly applied in the aviation, aerospace and military fields, and gradually extended. Because of the hard and brittle SiC particles contained in this material, mechanical machining is difficult, but EDM does have some advantages. To the same kind of moderate volume fraction (45%) SiCp/Al material, a comparative test was conducted using two kinds of processing methods, traditional EDM (the former) and PMEDM (the latter). Effects of the electrical parameters of both processing methods on the material removal rate (MRR) were analyzed and compared. After processing, the surface roughness value of the former is Ra1.386μm while the latter is Ra0.406μm which is only 29.3% of the former. The surface hardness was also tested by the MTS nano indenter: the former is about 1.7GPa, and the latter is about 2.2GPa which is 1.3 times of the former. Finally, to the machined surface, the micro-topography and the component of ‘white point’ were observed and analyzed by using scanning electron microscope (SEM) and energy spectrum respectively. Experiments and investigation results show that the PMEDM has a better performance compared with traditional EDM in improving the roughness, hardness and so on. So PMEDM will have a great potential in the processing of aluminium matrix composites.

Abstract: The particles dispersed in gap can increase the discharge stability and reduce discharge energy density in powder mixed EDM, which effectively improve the surface quality of machined workpieces. Concentration and distribution of particles computed by finite element methods in working conditions were simulated and corresponding experiments were done. The activities of particles in the discharge process were analyzed by experiments and theories. The results show particles have group effect in the gap and that the effect closely associates with particles concentration.

Abstract: Two kinds of specimen made of a kind of Ta-W alloy material with high melting point about 3000°C were processed by a traditional EDM (TEDM) and a powder mixed EDM (PMEDM) separately, and its surface characteristics were tested. After processing, their surfaces had the roughness of Ra 0.542μm and Ra 0.174μm, respectively. Moreover, their surface wear-resistance was studied on a CJS111A friction and wear tester. The micro-appearances on the wear surfaces were observed and analyzed by using a SEM. The test results indicated that the better wear-resisting ability the specimen, the higher wear rate displayed during the test the grinding balls. The wear rates of grinding balls corresponding to the two processed surfaces are 2.4×10-5 mm3/m for the TEDM and 1.4×10-4 mm3/m for the PMEDM, and the latter is 5.8 times of the former. The results show that the PMEDM is better at improving the wear-resistance, roughness and hardness than the TEDM, which means that the technique of PMEDM has a great potential in processing the special material.

Abstract: Effects of additive powders on the machining mechanism of powder mixed EDM were researched. The whole discharging process was discussed based on theory of plasma and dielectric. Experiments, oscillograms and energy spectrum analysis gotten in experiments were performed in order to examine the changes of discharge between EDM and powder mixed EDM.

Abstract: Powder mixed EDM can effectively improve the surface quality of a machined workpiece. In order to study the mechanism of powder mixed EDM process, particles’ activities in working conditions are simulated and corresponding experiments are done. A 3D electric fields model described by finite element method of the particles suspended in working fluid in the electric field is built, the generated field is computed and presented, and the activities of particles in the breakdown process are analyzed. The results show that this method can serve as a good way to learn the activities of particles in the breakdown of discharge.