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EDM Machine or EDM is a non-traditional method of removing material from a workpiece by means of heat energy. Like processes such as laser cutting, EDM does not need mechanical force in the removal process. This is the reason why it is considered non-traditional, unlike, for example, machining with cutting tools.
EDM is very popular in the production of tools and molds due to its use especially for hard materials such as titanium, or for particularly complex shapes that are difficult to achieve when milling.
Ecyclopædia Britannica gives a brief explanation of EDM:
"An EDM involves directing high-frequency electrical discharges from a graphite tool or soft metal that serves as an electrode to break down conductive materials such as hardened steel or carbide."
Put simply, EDM is a production process that precisely removes material from conductive materials using an electrode. Similar to pressing the mold into a soft material, the electrode leaves a negative impression on the workpiece. The physical process is a bit more complicated: a small gap between the workpiece and the electrode discharges, which removes the material by melting or evaporation. In this process, the electrode and workpiece should be immersed in a dielectric fluid.
The basis of this process is the ability of controlled electric sparks to erode the material. The workpiece and electrode do not touch during this process. Between them is a gap as thick as human hair. The amount of material removed using one spark is small, but the discharge occurs roughly several hundred thousand times per second.
While the electrode is moved closer to the workpiece, the electric field in the gap, also called the spark gap, increases until it reaches the puncture volume. In this process it is necessary that the fluid in which this discharge occurs is not conductive or dielectric. The discharge causes high heating of the material, melting small amounts of material. This excess material is removed with a constant flow of dielectric fluid. The liquid is also useful for cooling during processing. In addition, it is necessary to control sparks.
There are three different types of electrical discharge treatment. The one described above is called sinker EDM. It is also known as die sinking, cavity-type EDM, volumetric EDM, traditional EDM or frame EDM. Using Die sink EDM allows users to create complex shapes. This method requires electrodes (often made of graphite or copper) that are pre-treated to obtain the necessary shape. This electrode is then embedded in the workpiece, creating a negative version of its original shape.
The second type of electrical discharge treatment is called wire discharge and is also known as wire erosion, wire burning or spark discharge. In Wire EDM, thin wire is used to cut the workpiece. In this case, the wire acts as an electrode. During processing, the wire always comes from the automatic spool feeder. If the cut is to be made in the center, not outside of the workpiece, the EDM drilling small holes is used to make a hole in the workpiece, through which the wire is then threaded.
The wire is held with diamond guides. Usually deionized water is the fluid. The wire is often made of brass or copper.
The last type of EDM is called hole drilling. As the name implies, this process is used to drill holes. Compared to traditional drilling methods, EDM is able to process extremely small and deep holes. Additionally, drilled EDM holes do not require deburring. The electrodes in this process are tubular, and the dielectric fluid is fed through the electrode itself.
In general, any conductive material can be treated by electrical discharges. Typical materials include metals or metal alloys such as hardened steel, titanium and composites.
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