Effect of thermo-capillary (Marangoni) convection in Electronic Discharge Machining (EDM).

The mass and heat flows due to thermo-capillary (Marangoni) forces in a melt pool caused by a single discharge on a steel sample have been calculated using finite element analysis. The thermocapillary forces are found to modify significantly the geometry of the melt pool, to limit the evaporation of steel at the pool surface, and to induce convection with velocities exceeding 10 m/s. These results show that the thermo-capillary effect is important in the context of Electronic Discharge Machining (EDM). A scenario for matter removal that accounts for erosion rates measured in EDM operation is presented.