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Radmot May 7, 2024 7:57:11 PM

What is electrical discharge machining (EDM)?

The development of machining – especially numerically controlled – allows fast and repetitive manufacturing of even the most complex parts. Although there is a vast availability of modern technologies and solutions (e.g. 5-axis CNC mills) one of the biggest challenges for that industry remains machining and forming areas that are hard to access. 

The technological process that allows us to bypass such 'accessibility' problems – almost impossible to solve with traditional machining – is electrical discharge machining, EDM in short. That process is based on electrical erosion and allows it to shape surfaces that are hard to access. Such technology effectively is a perfect addition to the traditional CNC machines that – even the most professional – cannot achieve. 

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What is electrical discharge machining and what are the types of that process?

Electrical discharge machining (in short: EDM, also called wire erosion, spark eroding, die sinking, spark machining, or wire burning) is a metal shaping process that uses electrical erosion to form parts made out of conductive alloys.

💡 Such a process allows the formation of hardly accessible surfaces, details machining (e.g. internal sharp corners or threads in already hardened material), or tools regeneration (within adjusted work parameters.

Just like other forms of machining – it is a material removal process, but can be also used to fill chips in many surfaces. 

Usually, the electrical discharge machining uses an electrical field – created by working electrodes – to achieve impact ionization.Such a phenomenon creates high temperatures on the surface, creating the plasma channel and leading to material vaporization. In the EDM process itself are not created chips but fumes.That is the main reason why electrical discharge machining requires a very good head removal system. 

👉 Machining parts should be submerged in the dielectric – the fluid of very low electric conductivity – filtered and cooled. On top of that working area for the EDM should be ventilated to remove metal vapors. 

We can define two types of electro-erosion machining:

  • electrical discharge machining,
  • wire electrical discharge machining – WEDM – often also called 'wire cutting' or 'wire-cut EDM'.

These two methods differ mainly due to the type of working electrode – EDM uses traditional solutions. WEDM to transfer electricity to the surface of the machined element uses scrolled wire (thus 'wire' in the name). On top of that working parameters such as current, its level, or applications also differ. Due to the high precision of machining, EDM and WEDM are often used almost exclusively in numerically controlled devices – CNC. It is worth mentioning that the first WEDM machine was built in 1969, during the 3rd industrial revolution, which was caused by – among others – numerically controlled technology.


What does the electrical discharge machining look like?

The EDM machining can be subjected to parts made out of material that is electrically conductive, like steel, aluminum alloys, copper, etc. 

The process itself looks like this: 

Step 1
The machined element is submerged in the dielectric liquid (electrically neutral liquid). Traditionally – kerosene; more often – specialized oils or deionized water. That provides safety of the process and machining precision – electrical current affects only the machined surface, not the area around due to such liquid isolation.

Step 2
A working electrode is applied to the surface. Applied current causes impact ionization that leads to heating the machined area above the melting temperature of the machined metal. In effect, excess material is vaporized

Step 3
The electro-dielectric discharges are very rapid and violent. The effect of that process is liquid material ejection – intercepted by the dielectric liquid and filtered.

Step 4
Some EDM machining devices use special channels that continuously deliver 'fresh' (filtered and cooled) dielectric to achieve better heat removal and the remaining metal particles from the working area. Such processes used copper or graphite electrodes (for WEDM – wire made of these materials).


Due to thermal modification of the surface, further processing of EDM machined parts can be problematic – for example sanding/grinding. That is why in the process of choosing the best machining process it is worth contacting a specialized CNC factory like RADMOT.

What are the applications of EDM in material machining?

A common feature of EDM I WEDM is the possibility of machining surfaces that are hard to reach or materials that are hard in machining (eg. hardened steels or polycrystalline diamonds). That is why such machining a method is often used in following the industries:

  • production of metal parts and elements – the possibility to machine inside surface allows precision shaping of matrices and injection forms insides, 
  • parts manufacturing – booths their production (with WEDM) and regeneration (in other words – restoration to the initial form), 
  • automotive industry – EDM allows precision machining of the engine's internal combustion and housings for the electrical), same as housings and other types of internal – but hard to regard-to-reach especially monolithic (e.g. turbocharges or compressors), 
  • airplane industry – eg. to manufacture turbine blades,
  • medical industry – for precision tools manufacture, 
  • electrical industry – transform transformation photovoltaic frames, 
  • others that require high precision of the internal machining, especially made of materials that are hard to mill (e.g. cemented carbide – used for tool manufacturing or very hard tool steels).


EDM and WEDM – key differences

The division mentioned above (electrical discharge machining and wire EDM) is based on a few features of both processes. In addition – each uses different types of current. The key difference between these two processes is visible in the machining process itself:

  • EDM is used to form complicated shapes, but in materials that are susceptible to traditional CNC machining. In many areas – is used as a 'complementary manufacturing' due to shaping areas that are inaccessible with traditional CNC machines. 
  • WEDM allows the shape of materials that are not as susceptible to machining, especially tools (e.g. saw blades or mill cutters) made of very hard metal alloys. Machining of those materials with traditional CNC devices can be problematic and lead to faster tool degradation.


One order, many benefits – this is how you collaborate with RADMOT

At RADMOT, we offer CNC milling services, CNC turning services, as well as a variety of additional services including washing, aluminum anodizing, laser marking, and assembly. We have over 80 modern machines at your disposal in our machine park, all from reputable manufacturers. Download the presentation and check on which machines we produce parts.

Contact us and tell us what you need. We have been providing CNC services for almost 40 years. Our quote is completely free. And if you have doubts about which technology will work best for you, our expert knowledge is at your service.

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