Coloring Galvanized Wire
Q. I am currently working on a project for a client who wishes to in-line color galvanized steel wires. The idea is to design a system that paint the wires. At this stage, we are looking for suitable paints and painting techniques that would serve the purpose.
The main constraints for coloring the wires are quick curing (about 3 sec) and coating thickness <10 µm. Can you suggest any possible technique that will paint the wires? For example, is wet spray using electrostatics a possible solution? J. L.
A. Wire coating is a well-known process that produces electrically insulated conductors for the electrical and electronics industries. For example, many devices ranging from small coils to large electric motors use miles of insulated magnet wire.
The electrical insulation is applied using a relatively simple machine called a wire tower. It consists of a payout reel, upper and lower sheaves, pretreatment section, coating head, curing oven and takeup reel.
The key areas are the pretreatment section, the coating head and the curing oven. Pretreatment varies with the type of wire coated. The coating head consists of a liquid trough and coating dies. The wire passes through the trough, picking up the coating. in the process, then passes through dies that control film thickness. Coated wire goes through a thermal or UV curing oven. Cured wire passes over an upper sheave and down to a lower sheave, and if necessary, to another larger diameter die for another coat. Otherwise it goes directly to a take-up reel. The number of passes, upper and lower sheaves and dies used depends on the required film thickness.
This equipment applies electrical insulation manufactured using a wide range of coating resins such as thermally cured liquids, UV-cured liquids and powder coatings. Wire towers are highly specialized pieces of equipment. Although suppliers of this equipment are not specifically listed in the PRODUCTS FINISHING DIRECTORY AND TECHNOLOGY GUIDE, the listing of suppliers of finishing systems, paint, porcelain enamel, powder or conveyorized, listed on pages 278–280 of the 2007 edition should be able to help you.
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