This technique exploits the capacitive properties of the
electrical double layer (EDL) at the electrode/electrolyte interfaces:
it has been demonstrated that the electrical model of
the electrochemical cell is a RC circuit [11–15]. The charging
constant (τ=RCDL, where CDL is the overall capacitance of the
cell and R is the electrolyte resistance) of the EDL depends on
the distance between the tool and the workpiece (which actually
corresponds to the charging current path): the further the
tool is from the workpiece surface, the longer the charging
time of the EDL will be. By using this property, the
localisation of the material removal can be controlled very
accurately by setting the pulse duration according to the
charging time of the EDL.
This machining technology is being developed to meet the
increasing demand driven by progress made in aerospace
(aero-engine blades [16] and gas turbine blade cooling system
[17]), microelectronics [18], automotive (requirement for
smaller fuel injection nozzles holes with complex shape in
combustion engines), electronics (miniaturization of components),
medical and biomedical fields [19–21]. It enables the
machining of micro-size features with high accuracy and high
aspect ratio in materials with high hardness and stiffness (or in
the materials that are very hard to machine conventionally
because they are very brittle such as Indium Antimonite