A Thermo-hydraulic Modeling for the Formation Process of the Discharge Crater in EDM

Abstract

In EDM, the extremely high thermal power density results in melting and evaporating followed by removal electrode material, forming a discharge crater on electrode surfaces. Thus, during the formation process of discharge crater, there are the three physical forms (including solid, liquid and vapor) of electrode material and the different phase transformation between them simultaneously. In order to clarify the processes of discharge crater formation and material removal in electrical discharge machining (EDM), in this paper, the thermo-hydraulic coupling numerical model of discharge crater formation was established and analyzed with finite element method (FEM). The model is based the theory of Multi-physics coupling related to the electrode material removal process, and the equations of heat conduction and fluid flow were coupled. In addition, the level set method was used to track the variation of the discharge crater surface. The simulation of the processes of discharge crater formation and material removal in EDM were realized. The temperature distribution, the velocity distribution and the acceleration distribution of heated zone were analyzed. It can be found that after discharge is ignited, material removal began to occur. It was also found that the metal removal efficiency was 0.04, leaving most of the molten zone re-solidified. It can be considered that the flow flied formed in the heated zone is one of mechanisms of the material removal and the forming of the discharge crater.