Gap effect in electrochemical jet machining

Abstract

Electrochemical jet machining (EJM) is a young-generation micromachining and surface texturing technique with multiple merits. The materials removal function in EJM has traditionally been considered to be Gaussian-like and unaffected by changes in inter-electrode gap when maintaining a constant machining current. Nonetheless, phenomena that contradict this widely accepted perception are sometimes observed. In this paper, to clarify the inter-electrode gap effect in EJM, its impacts on flow field, electric field, and machined shape were studied by both experiments and simulation. With varied gaps ≥0.4 of nozzle diameter the jet profile keeps almost same and only its length changes, while narrowing the gap from 0.4 to 0.2 of nozzle diameter causes thinning of the jet-surrounding-film. Jet profile required for EJM cannot form with an overly tiny gap. In addition, the gap ≥0.6 of nozzle diameter features sufficiently long cylindrical jet portion that uniformly distributes the pass-through current density and eliminates the cathode-shape-determined electric field near nozzle to act on workpiece, resulting in constant materials removal function even though gap changes. With smaller gap the cathode-shape-determined electric field affects the anodic current density distribution and the materials removal function can be modulated by adjusting the gap, allowing EJM to generate geometry other than Gaussian-like profile. Furthermore, the influence of inter-electrode gap when using the specially-shaped nozzle was also investigated. With a small gap this method performs its ability in modulation of materials removal distribution by designing nozzle shapes, while a large gap such as ≥ nozzle diameter enables it to operate as a conventional nozzle.