Experimental Research On EDM Using Conductive Polymer Composite Electrode

When electrical discharge machining (EDM) is used to process complex microstructures, the manufacturing process of the tool electrode usually is complicated, and the cost is high. Conductive polymer with characteristics of polymer materials of variable structure, easy to shape, can be formed through injection forming, extrusion molding and embossing, also can be secondary processed in the form of stretch and twist, which can realize rapid manufacturing complex micro electrode, and breakthrough the limitation of the conventional electrode size. In this paper, the conductive polymer was used to make tool electrode, and the effects of EDM with different process parameters were studied. The main research works are as follows:Firstly, in order to obtain conductive polymer materials with good conductivity, effects of conductive fillers and processing parameters on the electrical conductivity were studied. The silver-plated copper powder and the carbon fiber were adopted as conductive filler, and epoxy resin was used as polymer matrix. Results show that, carbon fiber filled conductive polymer are more likely to form the conductive network compared with silver-plated copper powder filled type, whereas its minimum resistivity are about two orders of magnitude lower. In addition, the processing parameters for conductive polymers also have certain effects on the conductivity of materials, such as stirring time, vacuum and vacuum time, embossing pressure, etc.Secondly, the tool electrode was made by embossing using conductive polymers, and the influence of different process parameters on EDM performance was studied. Results found that the influence of process parameters on EDM characteristics using conductive polymer electrodes are similar to the traditional electrode materials. The influence of peak current and pulse duration on the processing speed, surface roughness and electrode loss is obvious, and pulse interval mainly affects the processing speed and the process stability. In addition, when the silver-plated copper powder content is above 60%, the epoxy resin matrix conductive polymer electrode can obtain relatively high processing speed, but the electrode loss is serious. In addition, the feasibility of the conductive polymer composite electrode was verified through EDM experiment.Finally, in order to improve the corrosion resistant ability of the conductive polymer electrode in EDM, the surface of the electrode is treated by copper plating. Results found that with the increasing of bath temperature, the stirring speed, the average of current density and the pulse duty ratio, the deposition rate increases. When bath temperature is 30 ℃, stirring speed is 400 r/min, average current density is 3 A/dm2, and pulse duty ratio is 20%, the deposition quality is relatively better. When the conductive polymer composite electrode, which surface was copper electroplated, was used in EDM, the discharge process is more stable. Although the processing speed is relatively slow, less electrode loss and better surface roughness can be obtained.