Abstract:In this present research work, a new modelling of energy density in EDM (Electrical Discharge Machining) is proposed. Energy density can be defined as the amount of energy needed to get a unit volume of material removed, and for its modelling, the whole EDM process has been taken into account. This new definition lets us quantify the energy density that is being absorbed by the workpiece and the electrode. Results are compared to those obtained by die sinking EDM in an Inconel ® 600 alloy using Cu-C electrodes. Currently, this material is of great interest for industrial applications in the nuclear, aeronautical and chemical sectors, due to their combinations of good mechanical properties, corrosion resistance and extreme hardness at very high temperatures. The experimental results confirm that the use of negative polarity leads to a higher material removal rate, higher electrode wear and higher surface roughness. Moreover, the optimal condition to obtain a maximum MRR (Material Removal Rate) of 30.49 mm 3 /min was: 8 A, 100 µs and 0.6, respectively, for the current intensity, pulse time and duty cycle.

In the present doctoral thesis the analysis and the modeling of the most influential parameters on the EDM of three low machinability materials are dealt with. Specifically, the study is focused on the alloy Inconel® 600 (Special Metals Corporation) and on the ceramics titanium diboride (TiB2) and siliconised silicon carbide (SiSiC). Nowadays, these materials are of great interest for industrial applications in the aeronautical, nuclear and automotive sectors, due to the combination of good mechanical properties, corrosion resistance and extreme hardness at high temperatures. To carry out this study, Design of Experiments (DOE) techniques are used in order to plan and to select the values for these parameters, as well as, to obtain mathematical models to predict the optimum machining conditions. Moreover, the technological tables for such materials are determined in function of the following design factors: current intensity, pulse time and duty cycle, in the study ranges considered. From these tables, it is possible to achieve a certain surface quality based on two machining strategies: a machining strategy that maximises the material removal rate and other that minimizes the electrode wear. To obtain the technological tables, experimental values are used and, in those cases where it is not possible to provide data, nonlinear optimization methods are employed to predict these values, by using the generated mathematical models, based on the experimental results. Furthermore, scanning electron microscopy (SEM) is used so as to obtain information of the topography of the resulting surfaces after the EDM process. Finally, a new parameter called ‘energy density’ is proposed for further research in the EDM process.

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