There are three different types of electrical discharge machining. The one described above is called sinker EDM. It is also known as die sinking, cavity type EDM, volume EDM, traditional EDM, or Ram EDM. Using Die sink EDM allows users to produce complex shapes. This method requires electrodes (often made from graphite or copper) that are pre-machined to have the necessary shape. This electrode is then sunk into the workpiece, creating the negative version of its original shape.


The second type of electrical discharge machining is called wire EDM and is also known as wire erosion, wire burning or spark EDM. In Wire EDM a thin wire is used to cut the work piece. In this case, the wire works as the electrode. During the machining, the wire is constantly coming from an automated feed with a spool. If the cut has to be made in the middle rather than the outside of the workpiece, small hole drilling EDM is used to make a hole in the workpiece through which the wire is threaded afterwards.


The wire is held with diamond guides. Usually the liquid is deionized water. The wire is often made from brass or copper.


The last type of electrical discharge machining is called hole drilling EDM. As the name suggests, this process is used for drilling holes. Compared with traditional drilling methods, EDM is able to machine extremely small and deep holes. Additionally, EDM drilled holes don’t need any deburring. The electrodes in this process are tubular and the dielectric fluid is fed through the electrode itself.


In general, every conductive material can be machined with electrical discharge machining. Common materials include metals or metal alloys such as hardened steel, titanium, and composites.


Typically, the electrodes for die sinking EDM are made of copper or graphite. The main factors that influence the decision for an electrode material are the electrode’s conductivity and its resistance to erosion. Graphite has the advantage that it is easier to machine than copper. However, copper is highly conductive and strong. Brass, an alloy of cupper and zink, is often used for wire EDM or small tubular electrodes.


Contrary to electrodes for die sinking, the wire used for wire EDM does not have to offer good resistance characteristics, as new wire is fed constantly duting the cutting.


Advantages: When Applying EDM Makes Sense

The main advantage of electrical discharge machining is that it can be used on any material as long as it is conductive. It is therefore possible to machine workpieces made from tungsten carbide or titanium that are hard to machine with traditional cutting methods. Another advantage of electrical discharge machining is the lack of mechanical force put into the workpiece. Fragile outlines are easier to produce because there is no high cutting force needed to remove the material.


EDM also allows for shapes and depths that are impossible to reach with a cutting tool. Especially deep processing where the tool length to diameter ration would be very high is a usual application for EDM. Sharp internal corners, deep ribs and narrow slots are other specialties of electrical discharge machining. Another argument for using EDM is that the surface finish is usually better than with traditional methods. Electrical discharge machining produces surfaces with a fine finish and high precision.


Moreover, EDM allows users to machine hardened workpieces. Whereas other machining techniques need to be executed before the workpiece is hardened with heat treatment, electrical discharge machining can be applied on the hardened material as well. Thus, any potential deformation from heat treatment machining can be avoided.


However, there are numerous examples where electrical discharge machining is not the right solutions. EDM is a high precision machining method. EDM is a rather slow method compared to traditional machining. High-volume tasks are therefore not suited for this method. At the same time, the electro thermal process requires high power consumption.


Similar to traditional chipping methods, the tool life in EDM is not endless. In sinker EDM, the electrode is also vulnerable to erosion. Because of the tool wear, the electrode has to be replaced regularly. In sinker EDM, it is also necessary to produce the correctly shaped electrodes before the workpiece can be machined. This is an additional step compared to machining processes with traditional cutting tools.


If you have interest or requirement of electric discharge machine, I recommend you to visit Ocean Technologies Co., Ltd. – they are the professional manufacturer of specializing in EDM machines. Welcome to check out their website and feel free to contact with Ocean for more details!


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