EDM: A Machining Process

Electrical Discharge Machining (EDM)

Another great example of how technological advances have improved upon traditional machining processes is Electrical Discharge Machining (EDM). EDM enables you to remove material by immersing a part in water and to create a very high voltage between a piece of copper or graphite and the part so that sparks jump between them. The sparks are so hot that they cut away metal from the part. The main advantage of EDM is that it can be used to cut any metal as long as it conducts electricity. EDM can cut small or odd-shaped angles and intricate contours and because it does so without ever touching the part the accuracy of EDM is extremely high.

The Electrical Discharge Machining process is frequently used in mold-making and tool and die applications. Other frequent applications include prototyping and low volume production runs that would cost prohibitive utilizing other more labor intensive machining processes.

There are two common kinds of EDM:

  1. Wire EDM
  2. Ram EDM.

Wire EDM

In wire EDM, the copper cutting tool is a wire that is guided by a computer-controlled machine. The wire cuts a thin line through the part. Many shapes can be produced this way in flat material. The wire-cut EDM uses water as its dielectric. Proper flushing of the Electrical Discharge Machining environment is required to prolong tool life. Filters and de-ionizing units help to control the water’s resistivity to ensure that the EDM process works at peak efficiency.


More complex shapes can be formed by ram EDM. Ram EDM uses a negatively shaped copper or graphite electrode, which slowly descends into the part as it cuts leaving a precise impression in the part. The advantage to ram EDM is that it can produce parts with very complex geometry in materials that are hard to work. The disadvantage is that this takes a very long time and sometimes several copper or graphite tools must be made because the sparks eventually wear away the copper or graphite as well. To maintain or prolong tool life in the Electrical Discharge Machining process it is imperative to continuously flush residue from the work environment.

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