Spark Machining or Electro Discharge Machining is used on hard metals, especially the processes that are very difficult for traditional techniques to penetrate. Metal is removed from a workpiece by a rapid succession of constant electrical discharges.
As the material is removed from the original workpiece, a continuous flow of fluid (which is usually de-ionized water or dielectric oil) washes it away. This repetitive process continues, until the final shape is created and completed.
A major (and very important) limitation to this process is that it ONLY works with material that is electrically conductive.
Two main methods of Electro Discharge Machining
They are “ram” and “wire”, and the primary difference is the electrode that is used during the machining process.
A “ram” edm cutting application uses a graphite electrode and a traditional tool. This specially shaped electrode is connected to a power source, and is slowly fed into the original workpiece. This entire process is completed under water, and the fluid serves several purposes including:
- Flushing away of cut material.
- Serving as a coolant, to prevent overheating and potential damage to the workpiece.
- Acting as a conductor between the electrode and the material/workpiece.
When a “wire” edm cutting application is used, a tiny thin wire (usually brass) is used as the electrode.
Wire electro discharge machining is an alternative to manual and CNC milling methods, and allows the skilled operator to use the edm supplies, to create intricate designs that would otherwise be impossible.
If you were to observe the wire edm cutting process under a microscope, you will see that the wire doesn’t make contact with the metal piece being cut. The path that the wire follows is controlled via computer, and this allows for complex shapes and designed to be created.
A more simplified way to describe this method is to compare it to: a thin piece of wire being stretched between human hands and used to slice a block a cheese, and continuing to do so, until the desired design is completed.
Although similar in concept, when wire is dragged through cheese, the excess cheese is “displaced”, but when using this edm cutting method, the excess pieces that are being cut away are removed. In addition, this type of cutting method is used in some of the hardest materials in the industry. This type of edm cutting is used, when a low volume of molds are needed as a prototype.
These methods may take a little longer to complete, than traditional cutting methods, but the results are more precise, and you may not have to purchase as many replacement edm supplies, because this slower edm cutting method allows for the tool to last longer.