Modeling of thermal processes of a single crater formation by discharges of modern generators of EDM cutting machines

The peculiarities of forming a single crater geometry and heat affected zone depth during wire electrodischarge machining of a high-quality structural steel 45 on machines equipped with modern current generators are considered. With the help of mathematical modeling based on numerical solutions of the axisymmetric quasi-three-phase nonlinear thermal conductivity problem with moving phase boundaries, the curves describing the phase boundaries of the evaporation, material melting and austenitic transformation temperature, depending on energy parameters of the discharge and material thermophysical properties are received. The volumes of the material removed from the crater in the form of steam and liquid are estimated. The data on the energies spent on the phase transformation of the anode material: the melting and evaporation, their share in the total discharge energy applied to the steel anode at different processing modes, as well as the consequences of changing the pulse parameters in each mode are given. It is found that the increase in the pulse duration with increasing the total energy consumed in the electrode gap, leads to the efficiency decrease of overall energy usage for the destruction of the workpiece material. The adequacy of the model is evaluated by comparison with the experimental data, which have been repeatedly confirmed on the equipment of various enterprises. The obtained results open a promising way to minimize energy costs for the processing of materials and control the characteristics of the treated surfaces both in terms of the formation of microgeometry and the depth of structure changes in the heat affected zone. This, in its turn, will allow to expand the limits of the erosion technology application by increasing economic benefits from the use of the described method. In addition, the above-mentioned creates preconditions for new effective designs of technological modes of subsequent electrochemical dimensional machining with a fixed wire electrode, since the depth of the heat affected zone is an important factor in determining the allowance which needs to be removed in electrochemical surface modification

electro-discharge machining; impulse energy; heat-affected zone