thumb|upright=1.4|Electrochemical machining (ECM) diagram.<br/>1: Pump <br/>2: [[Anode (workpiece)<br/>3: Cathode (tool)<br/>4: Electric current<br/>5: Electrolyte<br/>6: Electrons<br/>7: Metal hydroxide

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Electrochemical machining (ECM) is a method of removing metal by an electrochemical process. It is normally used for mass production and for working extremely hard materials, or materials that are difficult to machine using conventional methods. Its use is limited to electrically conductive materials. ECM can cut small or odd-shaped angles, intricate contours or cavities in hard and exotic metals, such as titanium aluminides, Inconel, Waspaloy, and high nickel, cobalt, and rhenium alloys. Both external and internal geometries can be machined.

In the ECM process, a negatively-charged (cathode) cutting tool is advanced into a positively-charged (anode) workpiece. Pressurized electrolyte is injected at a set temperature into the area being cut, at a feed rate equal to the rate of "liquefication" of the anode material. The gap between the tool and the workpiece varies within 80–800 micrometers (0.003–0.030 in.) As far back as 1929, an experimental ECM process was developed by W.Gussef, although it was 1959 before a commercial process was established by the Anocut Engineering Company. B.R. and J.I. Lazarenko are also credited with proposing the use of electrolysis for metal removal.

  • High surface quality may be achieved.
  • No direct contact between tool and work material so there are no forces and residual stresses.
  • The surface finish produced is excellent.
  • Less heat is generated.

Disadvantages

  • The saline (or acidic) electrolyte poses the risk of corrosion to tool, workpiece and equipment.
  • It cannot be used for soft materials.

Currents involved

The needed current is proportional to the desired rate of material removal, and the removal rate in mm/minute is proportional to the amps per square mm.

Typical currents range from 0.1 amp per square mm to 5 amps per square mm. Thus, for a small plunge cut of a 1 by 1&nbsp;mm tool with a slow cut, only 0.1 amps would be needed.

However, for a higher feed rate over a larger area, more current would be used, just like any machining process—removing more material faster takes more power.

Thus, if a current density of 4 amps per square millimeter was desired over a 100×100&nbsp;mm area, it would take 40,000 amps (and much coolant/electrolyte).

Setup and equipment

thumb|upright|An ET 3000 ECM machine by INDEC of Russia

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ECM machines come in both vertical and horizontal types. Depending on the work requirements, these machines are built in many different sizes as well. The vertical machine consists of a base, column, table, and spindle head. The spindle head has a servo-mechanism that automatically advances the tool and controls the gap between the cathode (tool) and the workpiece.