Oxidized tool electrodes for optimized electro-discharge drilling

The production of components for automotive and aerospace industry by conventional machining is still limited by hardness and strength of the workpiece materials. Electro-discharge drilling is used for machining electrically conductive materials without any limitation due to mechanical properties. Electro-discharge drilling causes debris in the working gap, which leads to arcs and short circuits on the lateral surface with negative effects on processing results and process duration. Due to these arcs and short circuits limited drilling depth, increased tool wear, conicity of boreholes and process instabilities are still challenges in electro-discharge drilling. In this work, a new approach for passivation of the tool electrode material by oxidation is shown. Different oxidation processes for tool electrodes made of brass were applied and analysed. Surface modified tool electrodes were used for electro-discharge drilling of Elmax, SuperClean from the company VOELSTAPINE AG, Linz, Austria. The investigation was carried out on the machine tool AGIETRON Compact 1 from the company AGIE SA, Losone, Switzerland, for machining of through holes with a depth of t = 33.5 mm using different surface modified tool electrodes with a diameter of d = 0.8 mm. First results show a reduction of the erosion duration by 20 % for the application of thermally oxidized brass. The investigation of different defined oxide layer thicknesses and electrical resistances for specific applications are part of this ongoing work. This work is funded by the German Research Foundation (DFG).