Vibration-assisted electrochemical machining: a review

Electrochemical machining (ECM) uses a direct current (DC) at high density of 0.5–5 A/mm2 which is passed through the electrolytic solution that fills the gap between an anodic workpiece and a pre-shaped cathodic tool. At the anodic surface, metal is dissolved into metallic ions and thus as the tool moves towards the workpiece at a constant feed proportional to the dissolution rate of the anodic surface, then its shape is copied into the workpiece. During ECM, the electrolyte is forced to flow through a narrow interelectrode gap at high velocity of more than 5 m/s to intensify the mass/charge transfer through the sublayer near the anodic surface. The electrolyte removes the dissolution by-products, e.g., hydroxide of metal, heat, and gas bubbles generated in the interelectrode gap. These machining by-products affect the process accuracy, efficiency, stability, and productivity. Ensuring the continuous flushing of these products is, therefore, essential. One of these methods is through the use of pulsed voltage. Introducing vibrational motion, at low or ultrasonic frequency, to the tool/workpiece or the machining medium became a viable alternative for the evacuation of the machining products during the vibration-assisted ECM (VA-ECM). Other attempts to further enhance VA-ECM performance include the proper tool design, addition of abrasive particles to the electrolyte medium, and use of magnetic flux assistance. This paper reviews the principles of VA-ECM, main research directions, process parameters, and performance indicators. Numerous fields of VA-ECM which include micro-slotting, micro-drilling, macro-drilling, electrochemical wire cutting (ECWC), polishing and finishing, and micro-tool fabrication have been covered. Several mathematical and statistical modeling and optimization techniques have been also examined. The current paper also outlines possible trends for future research work.