Thin copper wires are made by pulling a thicker copper rod through a series of progressively smaller dies, a process known as wire drawing.
Here's a breakdown of the process:
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Preparation: Copper rods, typically produced through casting or extrusion, serve as the starting material. These rods are significantly thicker than the final desired wire diameter.
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Pointing: One end of the copper rod is tapered or pointed to allow it to be easily fed through the first die.
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Drawing Process: The pointed end of the copper rod is inserted through a die, a hard, wear-resistant material (like tungsten carbide or diamond) with a precisely sized hole. A drawing machine grips the pointed end on the other side of the die and pulls the copper rod through the die. This process reduces the diameter of the copper and elongates it.
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Multiple Dies: Because the copper can only be reduced by a certain amount in a single draw without becoming brittle or breaking, the wire is passed through a series of progressively smaller dies. This gradual reduction in diameter allows the copper to maintain its integrity and desired properties. Often, multiple dies are arranged in a "drawing block" where the wire wraps around rotating drums (capstans) between each die to provide tension and cooling.
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Lubrication: Lubricants are used throughout the wire drawing process to reduce friction between the copper wire and the die. This minimizes wear on the dies, prevents the wire from overheating, and improves the surface finish of the wire.
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Annealing (Optional): The cold working involved in wire drawing can make the copper harder and less ductile. To restore its ductility and improve its electrical conductivity, the wire may be annealed (heated to a specific temperature and then slowly cooled) between drawing stages or after the final draw.
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Spooling: After the final drawing stage, the finished thin copper wire is wound onto spools or reels for storage and transport.
In summary, the wire drawing process relies on the copper's ductility, combined with the application of force through successively smaller dies, to create thin, flexible wires with precise dimensions.
