electrode material. Graphite has certain properties quite different than metal based electrode materials: Graphite has an extremely high melting point. Actually, graphite does not melt at all, but sublimes directly from a solid to a gas at a temperature thousands of degrees higher than the melting point of copper. This resistance to temperature makes graphite an ideal EDM electrode material. Graphite has significantly lower mechanical strength properties than metallic electrode materials. It is not as hard, strong, or stiff like metallic electrode materials. However, since the EDM process is one of relatively low macro mechanical forces, these property differences are not often significant. Due to the significant differences between metallic electrodes and graphite, there are certain properties, unique to graphite. These properties are- Particle Size: Generally, the smaller the particle size, the better the mechanical properties of the graphite, resulting in finer detail, better wear, and better workpiece surface finish. Density: Since graphite is a porous material, its density must be closely controlled. Generally, higher density is preferable. Flexural Strength: Flexural strength is a measure of the strength. Generally, graphite with the smallest particle size has the highest flexural strength. Hardness: Hardness is generally a function of the particle size, porosity, and binder material. Hardness can be very important to the success of machining and grinding operations. Graphite is widely used due to its significant production advantages over metallic electrode materials. Speed: Graphite is faster than copper in both roughing and finishing, usually by a factor of 2:1.
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