Generation of complex surfaces by superimposed multi-dimensional motion in electrochemical machining

In electrochemical machining the shape of the machined surface corresponds to the shape of the cathode and the applied electrical charge. In order to increase the flexibility of electrochemical machining for the generation of complicated surfaces, several investigations on the application of superimposed multi-dimensional motion were performed. In this study several possibilities for the application of superimposed multi-dimensional motions are shown and compared concerning the machining flexibility and tooling requirements. Detailed investigations were focused on Jet Electrochemical Machining (Jet-ECM) and Pulsed Electrochemical Machining (PECM). The results are discussed and compared with respect to these applications. The special characteristic of Jet-ECM is the high localization of electric current by continuously applying an electrolyte jet. Based on experiments of manufacturing plane surfaces, the variation of line spacing was derived as a suitable superimposed motion strategy. To realize this strategy, the cross-sectional profiles of planar Jet-ECM erosions were detected. The measured depths of these erosions were implemented in a mathematical model. To evaluate the developed model, various experiments for the generation of different complex surfaces were carried out in four steel materials. It could be demonstrated that the variation of the line spacing is suitable to generate complex surfaces and that the deviations of the produced geometries from the intended geometries are in a range of a few micrometers. In addition PECM, characterized by the application of voltage pulses combined with an oscillating cathode, was investigated. In this study a multi-dimensional motion based on a single-axis tool movement superimposed with a rotation axis is investigated experimentally. The superposition enables the generation of complex surfaces with helical symmetry while preserving the specific benefits of PECM. The machined samples show good surface quality and high dimensional accuracy.