Mechanism and characteristics of electrochemical machining using electrolyte absorbed in solid porous ball

Electrochemical machining (ECM) is a process that is widely employed to machine extremely hard materials. However, because of the fluidity of the liquid electrolytes used in conventional ECM, it is difficult to accurately limit the electrolyte distribution over the machining area to prevent the occurrence of stray-current corrosion. Therefore, in this study, to overcome this shortcoming, a non-conductive solid porous ball is used as an electrolyte absorption material in ECM. The electrolyte is absorbed by the porous structure of the ball, and an electrolyte film is formed on the ball surface generating current paths from the workpiece to the tool electrode while preventing the electrolyte from flowing freely in an undesired manner over the workpiece surface. Because the workpiece is not immersed in the electrolyte, only the area in contact with the electrolyte held in the porous ball is subjected to ECM, whereas the other areas of the workpiece remain unaffected. In this way, the electrolyte distribution is limited to the desired area. In this paper, a newly developed experimental procedure, its machining mechanisms, and applications are explained. In addition, several unsolved problems that occurred in the experiments are reported and discussed.