Experimental and theoretical investigation of machining with conductive powder reinforced polymer matrix composite electrode in electric discharge machining

The aim of this study is to develop an alternative electrode production method in order to make the electrode producibility easier and decrease the cost in electric discharge machining (EDM). For this purpose, after constructing a mould made of plaster, silicon or resin using the available model, it is attempted to spill the mixture composed of the matrix and conductive filler into this mould and to solidify it. In this study, polyester resin is chosen as the matrix and the dendritic-shaped pure copper powder, graphite powder, and their mixture are used as the filler in order to provide the conductivity. In order for the mixture to take a hardened rigid form in its mould in a short duration, two different chemical substances, namely, an accelerator and a freezer, are used. In order to decide on the most convenient electrode type by comparing the material removal rate (MRR) and tool wear rate (TWR), five diferent types of electrodes, namely, free copper-polyester (N-B/P), compressed copper-polyester (S-B/P), sintered copper-polyester (P-B/P), compressed copper-graphite-polyester (S-B/G/P), and sintered copper-graphite-polyester (P-B/G/P) are produced. After the machining process, İİH, EAH, and relative wear (RW) values are graphically demonstrated for each type of electrode. To find out the electrical characteristics of the N-B/P, S-B/P, and P-B/P type electrodes, their electrical resistances are measured by preparing disc shape samples from the ones used in machining and their electrical conductivity values are determined using these data. Afterwards, the percolation concentration, percolation conductivity, saturation limits, and form factor values of the electrodes are obtained by means of the characteristic conductivity-concentration equations. In the study, the relationship of the performance of P-B/P composite electrodes which are the most convenient ones for pratical application with the grain size is examined. Furthermore, the relationships of the MRR and TWR characteristics of the composite electrodes with the concentration and grain size of the filler are derived as mathematical equations. This is the unique study as applying of composite electrode produced by the ortoflatic polyester as matrix and dendritic shape pure copper powder as filler to EDM.