Electrical Discharge Machining is a machining method used to machine conductive materials that are difficult to machine with traditional methods. That is to say that EDMing can cut small or odd angles and intricate contours or cavities into even pre-hardened steel without the need of heat treatment to soften and then re-harden. Instead, they remove materials via a series of rapidly reoccurring electrical discharges between an electrode (the cutting piece) and the work piece in the presence of an energetic field. While the EDM cutting tool is guided along a path that is very close to the work piece, it never actually touches the piece. This is because a series of consecutive sparks produce micro-craters within the piece and remove the material along the path by melting and evaporation rather than by slicing or grinding.
In wire EDMing a thin strand of metal wire is fed through the work piece which is generally submerged in a tank of dielectric fluid or deionized water. This fluid helps to flush away cut material, while the wire uses electric currents to cut the conductive material with no need for further finishing or polishing. Wire EDMing is most commonly used when low residual stresses are desired.
Wire EDMing can be used to cut plates or create punches, tools and dies from any conductive material including metals that are too difficult to machine through use of other conventional machining methods (for example, metal alloys, graphite, carbide and diamond). The wire is held between upper and lower diamond guides that move in an X-Y axis controlled by a CNC. The upper guide can also move independently along the Z-U-V axis to allow for tapering and transitioning shapes.
In sinker EDMing, a work piece and electrode are submerged in an oil or dielectric fluid and both are connected to a power supply which generates an electrical potential between the two pieces. As the electrode approaches the work piece, it generates sparks that erode the base metal of the work piece (with several hundred-thousand sparks occurring per second).
Controlled cycles help to determine the amount of on and off time, which determines the depth of crater generated in the work piece as a result of the length of time the piece is exposed to sparks. The mechanics of this type of EDMing make it great for small or oddly shaped angles that are difficult to create by conventional machining methods.
Small hole EDMs are used to drill rows of holes into the leading and training edges of turbine blades that are used in jet engines and to create microscopic orifices for fuel system components as well as a variety of other applications. These EDMs can machine blind (or through existing holes) and bore their holes with a long brass or copper tube that rotates with a constant flow of distilled or deionized water flowing through the electrode to act as a flushing agent.
EDMs are frequently used in the aerospace, automotive and medical industries. If you would like to learn more about how your company might benefit from the use of a Sodick EDM, contact Brooks today for a demonstration or to discuss the nature of your business needs so that we can help you find the best machining equipment to aid your business on the road to success.