Helical electrodes for improved flushing conditions in drilling EDM of MAR-M247

The machining of precision holes in difficult to machine materials or alloys with high aspect ratios Ï and under consideration of the cost-effectiveness of the overall process is still a challenge. Electro-discharge machining (EDM) is predestined for such purposes. Flushing is one key factor for the precise machining of bore holes with high aspect ratios Ï. Nevertheless, the capabilities of the flushing conditions are often underrated regarding an improved process stability, an increased material removal rate VW, a decreased machining time tero, as well as the tool wear ÎIE. Therefore, the present investigation considers the influence of an outer geometry of cylindrical rod tool electrodes to improve the electro-discharge drilling process. Different electrodes made of brass, with helical flutes along the shank, are compared with the basic geometry, a cylindrical rod electrode, with respect to their flushing capabilities. All electrodes have an outside diameter d = 3 mm. It is suggested that the machining process will stabilise and the material removal rate VW will increase due to improved removal efficiency of erosion particles (debris). Through holes with a total depth h = 16 mm have been machined by use of Design of Experiments (DoE) approved process parameters in nickel based superalloy MAR-M247. By use of a helical shaped electrode the machining time tero was reduced by 39 % compared to the cylindrical rod electrode.