Electrical Discharge Machining（EDM) has long been used in the industry for highly accurate metal removal at a reasonable cost, making short work of more complicated jobs with new CNC controlled machinery. Its cost effectiveness comes due to the length of time it has been around, as well as the process being fully automated and, therefore, not requiring any human intervention apart from at the beginning or end of the process.
There are three main types of EDM used today and they are:
- Die Sinker EDM:Graphite electrodes form a ‘positive’ causing a spark and eroding the metal;
- Wire EDM:Uses a thin wire as an electrode, which is moved in a controlled manner;
- Hole Drilling:Creates holes by using a rotating metal tube to create the spark and supply fluid.
As the names imply, each process is undertaken in a slightly different way, although the basics of the EDM process remain the same – by eroding the metal using an electrical discharge, which is enabled by the use of a dielectric fluid to create a conductive environment. This fluid also removes waste particles of metal created during the EDM process, cools the working area and allows a set distance to be maintained between the electrode and the metal.
Dielectric Fluid
The fluid used in EDM is usually either deionized water, as used in Wire EDM, or a hydrocarbon oil, as used in Die Sinker EDM. Each fluid will be able to deliver the properties outlined above for a set period of time, although it is advisable that the fluid be changed at least every five years, so as to minimize contamination and prevent a reduction in efficiency.
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