ELECRO CHEMICAL MACHINING

•      ECM, a dc voltage (10-25 v) is applied across the gap between a pre-shaped cathode tool and an anode workpiece.

•      The workpiece is dissolved by an electrochemical reaction to the shape of the tool.

The electrolyte flows at high speed (10-60 m/s) through the gap (0.1-0.6 mm) to dissipate heat and wash away the dissolved metal

•      The material removal rate by ECM is given by:

      MRR = C Ih

      where, MRR=mm³/min,

      I=current in amperes,

      h=current efficiency, which typically ranges from 90-100%,

      C is a material constant in mm³/A·min.

•      Feed rate (mm/min): f = MRR / A₀

      Assuming a cavity with uniform cross-sectional area A₀

Advantages of ECM

•      The components are not subject to either thermal or mechanical stress.

•      No tool wear during ECM process.

•      Fragile parts can be machined easily as there is no stress involved.

•      ECM deburring can debur difficult to access areas of parts.

•      High surface finish (up to 25 µm in) can be achieved by ECM process.

•      Complex geometrical shapes in high-strength materials particularly in the aerospace industry for the mass production of turbine blades, jet-engine parts and nozzles can be machined repeatedly and accurately.

•      Deep holes can be made by this process.

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Limitations of ECM

E      ECM is not suitable to produce sharp square corners or flat bottoms because of the tendency for the electrolyte to erode away sharp profiles.

•      ECM can be applied to most metals but, due to the high equipment costs, is usually used primarily for highly specialised applications.

•      Complex cavities in high-strength materials, esp. in the aerospace industry for mass production of turbine blades.