Mechanism And Experimental Study On Cu/Ni Composite Electrode For Small Hole EDM

In the process of small hole EDM, tool electrode exist in different forms and degrees of material wear, in particular, the side edges of the electrode wear phenomenon is most serious, and a direct result of changes in the electrode shape produces taper, with the increasing machining depth, taper is more serious, further make small holes appear taper in the depth direction, affecting the processing quality of the holes. Therefore, exploring a way to reduce the tool electrode wear has become one of the small hole EDM technology must be addressed.Firstly, this paper studied the mechanism of small hole EDM, and then forms and process of tool electrode wear are analyzed. Based on the aforementioned analysis results, a conceive for reduce shape wear of tool electrode in the small hole EDM processing with wear-resist composite electrode was proposed, by thermal physical properties of the metal material impact on the amount of material erosion as the theoretical basis, analysis the resistance wear characteristics of the composite electrode. The results showed that enhancing the electrical erosion resistance of traditional tool electrode surface was able to effectively decrease the tool electrode wear, especially at the angularity of the end of the tool electrode.On the analysis of the composite electrode electrical erosion resistance results, and combined with the actual situation small hole EDM process, a new composite electrode was fabricated to enhance the electrical erosion resistance of surface material and used to maintain the tool electrode cylindrical shape unchanged in the hole machining process. A Cu tubular electrode as the substrate, a different type of material, Ni, which has the high electrical erosion resistance, was plated on the surface of the Cu electrode, and preliminary experiments of high speed small hole EDM. Experimental results strongly indicated the rationality of the theoretical analysis; and also showed that because of the Ni coating, the tool electrode wear was decreased significantly. As a result, there was obvious promotion of those to maintain the electrode shape unchanged and improve the quality, depth to diameter ratio and speed of the drilled holes.Based on the theory of the processing mechanism, and tool electrode wear is more serious as the starting point, some beneficial attempts have been made to decrease electrode wear in the processing of small hole EDM in this paper, which could provide a different way of thinking to analyze and research on the tool electrode wear and its impact on small hole during the processing to some extent. Ni and Cu lattice of the same type, and similar lattice constants, and plating easier and coating combined with strong as the basis, according to comparing Ni and Cu, their melting and vaporization produces a certain time lag at the same temperature, a new type of copper matrix nickel-plated composite electrode was fabricated, and this is a viable way to improve the shape of the tool electrode wear, improve the machining accuracy of the small holes, and depth to diameter ratio as well as processing speed.The main work is as follows:1. Study on small hole EDM mechanism. The machining condition changes in the process of EDM miniaturization and the influence of these changes on small hole EDM processing are analyzed. Though the characteristic analysis of the working fluid medium, a series of state changes of discharge gap under the impact of external energy when the discharge breakdown; the electrode material removal process and energy conversion problem are conducted.2. Study on tool electrode wear. Studied the different forms of tool electrode wear and the wear change process; by analyzing the factors affecting the tool electrode wear, the paper proposed a conceive to reduce electrode wear with wear-resist electrodes.3. Study on reducing tool electrode wear with the composite electrode and fabricating the composite electrode. By analyzing the specific reasons of tool electrode wear during small hole EDM processing, studied a composite electrode to compensate the wear of the tool electrode; coating a electrode erosion resistance metal material Ni on the surface of traditional Cu electrode using plating process, successfully fabricated a composite electrode of copper matrix nickel plating.4. Study on composite electrode for small hole EDM experiment. Experimental results prove that composite electrode effectively restrains the electrode wear to some extent, especially at the angularity of the end of the tool electrode, thus, improving the quality, and depth to diameter ratio as well as speed of the drilled holes.