Electro chemical machining

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Electro Chemical Machining (or ECM) is a method of working extremely hard materials or materials that are difficult to machine cleanly using conventional methods. It is limited, however, to electrically conductive materials. ECM can cut small or odd-shaped angles, intricate contours or cavities in extremely hard steel and exotic metals such as titanium, hastelloy, kovar, inconel and carbide.

ECM is similar in concept to Electrical discharge machining in that a high current is passed between an electrode and the part, through an electrolyte. The ECM cutting tool is guided along the desired path very close to the work but it does not touch the piece. Unlike EDM however, no sparks are created. The workpiece is eroded away in the reverse process to electroplating. Very high metal removal rates are possible with ECM, along with no thermal or mechanical stresses being transferred to the part, and mirror surface finishes are possible.

As far back as 1929, an experimental ECM process was developed by W.Gussef, although it took until 1959 for a commercial process to be established by the Anocut Engineering Company. Much research was done in the 1960s and 1970s, particularly in the gas turbine industry. The rise of EDM in the same period largely stopped research into ECM in the west, although work continued behind the Iron Curtain. The original problems of poor dimensional accuracy, and environmentally polluting waste have largely been overcome, although the process remains a niche technique. The cutting heads on all Philips 'Philishave' shavers are made using ECM.

The ECM process is most widely used to produce complicated shapes with good surface finish in difficult to machine materials, such as turbine blades. It is also widely used as a deburring process.