T4T – Plunge EDM


The plunge EDM process, Electrical Discharge Machining, is one of the EDM material removal processes and more generally of the family of material removal processes termed “unconventional.”

The removal of material from the bulk takes place by passing current from the machine, which is equipped with a generator, to the electrode system, which is connected to the machine head via an electrode holder.

This is a metal holder that acts as an interface between the machine and the electrode, which can be considered the actual tool in analogy to the most common machine tools for conventional machining.

Going into more detail, this technique consists, as the description itself suggests, in the removal by thermal erosion of metallic material using electric current which triggers, via the electrode placed at a constant distance from the workpiece, a series of repeated electrical discharges on the material every few µs.

In this way, the electrode generates an impression on the workpiece that forms its “negative” and the removed material is pulverized.

EDM machining is applicable on metallic materials that, appropriately placed on the machine’s work table, are immersed in a liquid commonly called “dielectric” (usually demineralized water) whose peculiarity is that it is an insulator between the work area and the surrounding environment.

The material of which the electrode is made is characterized by high conductivity, and for this reason copper, graphite, and tungsten alloys (for special applications) are usually used.


  • Shape of manufacturable geometries: free complex, customizable, two-dimensional and three-dimensional geometries
  • Absence of burrs from stock removal versus milling/turning
  • Absence of both normal and tangential cutting forces
  • Ease of access to the work area compared to conventional chip removal
  • Limited electrode system dimensions that can be customized as needed
  • Machining does not depend on the mechanical properties of the material (e.g., hardness, tensile strength) and allows machining of very hard materials, which is difficult for chip removal


The EDM process finds application in multiple areas of the manufacturing industry, from general mechanics, such as in the production of dies for cold sheet metal machining and forming, to the plastics industry and the bio-medical sector.

Of particular interest is its presence in both Oil&Gas and Power Generation and Aerospace where it is now increasingly used in key areas of turbine hot stages.


The theory behind this technology was perceived as early as around 1700 by physics scholars, observing lightning and realizing that it erodes materials with its electrical discharges

In 1943, Mr. and Mrs. Lazarenko, two scientists, had the idea of exploiting this destructive effect of electrical discharges to create a controlled process and apply it to metalworking.