Electrode wear pattern during EDM milling of Inconel 718

Abstract

Electrical discharge machining (EDM) is a well-known process, which is distinct from conventional machining methods thermal machining principle not susceptible to materials hardness and therefore is mainly used for difficult-to-cut materials. EDM milling is a relatively new method to machine complex geometries by using standard shape, cylindrical, rotary electrode. This method with some limitations of small radius of corners and edges can be used instead of the complex die-sinking electrodes and exclude electrode milling step from the production chain. Layer-by-layer machining strategy is typically used in EDM milling, while the influence of such a crucial parameter as the layer thickness to the machining conditions is barely addressed in the process optimization. The current work investigates in the wear pattern during EDM milling in order to optimize machining strategy and therefore to achieve higher shape precision and minimized milling time. Correlations in electrode wear pattern are investigated after EDM drilling, EDM milling, and electrode dressing. Geometries of the machined cavities are presented and analyzed. Through all investigations derived the conditions and optimization principles for the thickness of the machining layer. Electrode diameter, electrode type, and the process gap, as an outcome of servo control and open voltage, are considered. Finally, new correlations and machining strategy recommendations are proposed based on the obtained knowledge.