19-09-2017, 01:16 PM
Although EDM is widely used in the industry, little research has been done on the complex problem of accurately estimating machining time. Often, estimation errors of 200% and more are produced. This article presents a new concept for accurately estimating the machining time for sinking EDM operations. The concept is based on machine-dependent reference values in which a correction factor is applied to take account of deviations from the reference due to discharge and efficiency. A validation of the proposed concept showed that for the machining of prismatic cavity shapes an enormous reduction of the estimation error is achieved in comparison to the existing methods.
EDM, also known as spark machining, spark erosion, burning, sinking, spinning or erosion of wire, is a manufacturing process whereby a desired shape is obtained by using electric sparks (sparks). The material is withdrawn from the workpiece by a series of rapidly repeating current discharges between two electrodes, separated by a dielectric liquid and subjected to an electric voltage. One of the electrodes is called the tool electrode, or simply the "tool" or "electrode", while the other is called the workpiece electrode, or "workpiece." The process depends on the tool and the workpiece not making the actual contact.
As the voltage between the two electrodes increases, the electric field strength in the volume between the electrodes becomes greater than the resistance of the dielectric (at least in some places), which breaks, allowing current to flow between the two electrodes . This phenomenon is the same as the rupture of a capacitor (capacitor) (see also burst voltage). As a result, the material is removed from the electrodes. Once the current is stopped (or stopped, depending on the type of generator), the new liquid dielectric is normally transported to the volume between electrodes, allowing the solid particles (debris) to be drawn and the insulating properties of the dielectric restored. The addition of new dielectric liquid in the volume between electrodes is commonly known as "discharge." Further, after a current flow, the potential difference between the electrodes is restored to what it was before the fault, so that a further dielectric liquid interruption may occur.