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Metal Cutting_Copper Tungsten

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Copper Tungsten Alloy for EDM Electrode Material: A Top Down View INTRODUCTION Graphite has long been the preferred material for the majority of sinker EDM electrode applications due to its exceptional thermal resistivity and manufacturability. Graphite provides fairly good cutting rates, wears less than most metallic electrode materials, and improvements in machine design have made it possible to produce a surface finish on par with Copper. Equally, much of the early resistance—primarily due to the excessive dust that graphite produces—has been successfully resolved by new technologies for controlling it. But, before graphite there was metal. The good conductivity and structural integrity of many metallic electrode materials popularized them for use in the tube type power supplies and R/C generator circuits of early EDM processing. And today, despite the benefits of graphite, several metallic EDM electrode materials remain top of mind for electrode manufacturers—in particular, Tungsten Copper Alloy. But what unique benefits give it a place across industries? ABOUT MATERIAL PROPERTIES In order to understand the value of Tungsten Copper as an electrode material, it is necessary to first define the material properties that make for an ideal sinker EDM electrode. 1. Structural Integrity: Though EDM is often considered a "zero-force" process because mechanical stress, chatter and vibration do not directly affect the electrode, the degree to which the material can withstand the thousands of violent electrical sparks it is subject to, is critical to wear performance, and surface finish accuracy—especially in poor flushing conditions. 2. Conductivity: Because electrical current is responsible for material removal, conductivity of material is crucial to cutting speeds. 3. Thermal Resistivity: EDM is a thermal process; and accordingly the higher the melting point of a material, the better the wear rates. 4. Chemistry: The chemistry of an electrode material, which determines its polarity in relation to the workpiece can greatly affect the efficiency of the EDM process. Critical Concern When choosing Copper Tungsten material porosity, which can cause a bump in the EDM cavity, is of utmost consideration. Because of the disparity in melting points, Copper Tungsten cannot be traditionally alloyed. Instead, a powder metallurgical process binds the composition together into a pre-form, which is then sintered. Sintering causes the material to shrink, occasionally resulting in this common defect. One way to ensure proper quality is to use the Press-Sinter-Infiltrate process, where the powder mixtures is first pressed into a die cavity; the "green" form is then sintered at a high temperature to bond the material; and lastly the material is repressed with a copper slug, which finally infiltrates the composition. This time tested process ultimately eliminates porosity and ensures a quality, high-density preform. Copper Tungsten Alloy: The Top of Mind Electrode Material for EDMing Carbides A White Paper From Metal Cutting Corporation Page 1 of 2

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