Numerical study on the dynamics of an electrical discharge generated bubble in EDM

In this paper, the influence of hydrodynamic behaviour of dielectric liquid media around a rapidly growing small spherical bubble in the process of electrical discharge machining (EDM) between the tool and the workpiece on material removal from the workpiece is investigated. The tool and the workpiece are assumed as two parallel rigid boundaries with dielectric liquid between them. The boundary integral equation method is applied for numerical solution of the problem. Results illustrate the time dependent shapes of the bubble generated between the two parallel rigid boundaries due to the electrical discharge. Results also indicate that continuous growth of the gas bubble leads to a sharp drop of pressure within the bubble which results in the sharp pressure drop over the surfaces of the tool and the workpiece. This pressure drop over the surfaces of the tool and the workpiece causes expelling of the gas dissolved in the molten metal and helps the molten material to escape.