Electrochemical machining

Abstract

The history of electrochemical machining (ECM) is outlined, beginning with the basic 1929 patent of Gusseff, an outstanding visionary invention which recognized quite accurately the operating features of the ECM process. Early practical developments are described, leading to full commercial exploitation by Anocut in the 1960s. Recent specialized drilling applications in the aerospace industry are described, bringing the history up to date. The fundamental dynamics of the process are presented for plane-parallel gap conditions leading to the general analysis suitable for cathode tool design. The electrochemistry of the process is outlined, including the mechanisms of metal dissolution, their behaviour patterns, and their relationship with the Jacquet electropolishing curve. The machining rate limiting factors, including the rate of oxide film formation, are analysed. The effect of electrolyte acidity is examined, as is also the role of hydrogen ions in promoting breakdown of oxide films permitting higher machining rates. The nature of surfaces produced by ECM under various conditions is described, together with the resultant effect on mechanical properties. The ECM plant and its constituent units, including power supply feed systems and electrolyte handling equipment, are described, and the basic ECM operations such as shaping, drilling, turning, deburring, and grinding are considered. The review is concluded by outlining application experience and economics of the process in its practical realization in an industrial setting. A section is devoted to the prediction of possible future trends, and to those application aspects which would benefit from further research. Novel approaches to machine-tool design are suggested, aimed at higher plant utilization.