EDM is a method of processing using electricity and heat energy that was studied in the 1940s and gradually applied to production. EDM refers to the method of processing the workpiece through the electric erosion effect of the pulse discharge between the tool electrode and the workpiece electrode in a certain medium. Today we will learn about the principle of EDM.
The principle of EDM is based on the electro-corrosion phenomenon during the pulsed spark discharge between the tool and the workpiece (positive and negative electrodes) to remove excess metal to achieve the predetermined processing requirements for the size, shape and surface quality of the workpiece.
As shown in the figure, the workpiece and tool electrodes are respectively connected to two electrodes with different polarities of the pulse power supply. Tool electrodes are usually made of electro-corrosion-resistant materials with good conductivity, high melting point and easy processing, such as copper, graphite, copper-tungsten alloy and molybdenum. During the machining process, the tool electrode also has loss, but it is less than the erosion amount of the workpiece metal, and even close to no loss. As the discharge medium, the working fluid also plays the role of cooling and chip removal during the machining process. Commonly used working fluids are media with low viscosity, high flash point and stable performance, such as kerosene, deionized water and emulsion.
When the pulse voltage is applied between the two electrodes, when a proper gap is maintained between the workpiece and the electrodes, the working fluid medium between the workpiece and the tool electrodes will be broken down to form a discharge channel. The instantaneous high temperature is generated in the discharge channel, which melts or even vaporizes the surface material of the workpiece, and also vaporizes the working fluid medium. After Tulse discharge ends, after a period of time, the working fluid is restored to insulation. The pulse voltage is repeatedly applied to the workpiece and the tool electrode, and the above process is repeated continuously, and the workpiece material is gradually etched away. The servo system constantly adjusts the relative position of the tool electrode and the workpiece, and automatically feeds to ensure the normal progress of the pulse discharge until the required parts are processed.
