SURFACE QUALITY OF THE EDM PROCESSED MATERIALS
The article presents the importance of the EDM technology in the industry of machine building. It is mostly used in the machining of stamps and special processes in which the conventional technologies are inefficiently. It's known that only condition of machining with this method is that the material should be electro conductive. The main parameters that are followed during the process are the precision and the roughness of the surface. The collective tried to emphasise the importance variation of the roughness concerning some machining parameters. Some of the measurements were conducted at ETH Zurich using an electronic microscope.
Modeling of a Single Resistance Capacitance Pulse Discharge in Micro-Electro Discharge Machining
Micro-EDM (electro discharge machining) is a derived form of EDM process especially evolved for micro-machining. The use of resistance capacitance pulse generator, an advanced controller for machining in smaller interelectrode gaps and with lower discharge energies than in EDM, makes the material removal characteristics of a single discharge in micro-EDM different from that of the EDM. A comprehensive model predicting the material removal in a single discharge in micro-EDM is conceptualized. The model incorporates various phenomena in the prebreakdown period. It considers plasma as a time-variable source of energy to the cathode and anode to evaluate material removal at the electrodes. The plasma temperature and radius of the crater at the cathode (workpiece) predicted using the model were found to agree well with the experimental data in the literature.
A finite element model of EDM based on the Joule effect
Abstract A thermal–electrical model was developed for sparks generated by electrical discharge in a liquid media. A cylindrical shape has been used for the discharge channel created between the electrodes. The discharge channel being an electrical conductor will dissipate heat, which can be explained by the Joule heating effect. The amount of heat dissipated varies with the thermal–physical properties of the conductor; as a result, the maximum temperature reached is different. In the present model, the radii value of the conductor is a function of the current intensity and pulse duration. The thermal–physical values used in the model are the average of both the ambient and melting value. Copper and iron are the materials used for anode and cathode, respectively. The Finite Element Analysis (FEA) results were compared with the experimental values of the table of AGIE SIT used by other researchers [D.D. DiBitonto, P.T. Eubank, M.R. Patel, M.A. Barrufet, Theoretical models of the electrical discharge machining process—I: a simple cathode erosion model, Journal of Applied Physics, 66(9) (1989) 4095–4103; M.R. Patel, M.A. Barrufet, P.T. Eubank, D.D. DiBitonto, Theoretical models of the electrical discharge machining process—II: the anode erosion model, Journal of Applied Physics, 66(9) (1989) 4104–4111; P.T. Eubank, M.R. Patel, M.A. Barrufet, B. Bozkurt, Theoretical models of the electrical discharge machining process—III: the variable mass, cylindrical plasma model, Journal of Applied Physics, 73(11) (1993) 7900–7909]. In order to show the universality of the model it was obtained results for all current intensity values of the table. The Tool Wear Ratio (TWR) and Material Removal Rate (MRR) as well as surface roughness results agree reasonably well with the researcher's values found for that table and itself.