![]() Coating viscosities of 20 to 1,000 centipoises - and even higher with gapped or double wound rods - can be accommodated at line speeds of up to 3,000 feet per minute in paper mills and 1,000 feet per minute for most converting operations. ![]() The technique is universal enough to stand as the third most popular coating method, following gravure and reverse roll coating. They are also used to apply hot melt wax coatings, as well as in production of release paper, tape, wall coverings, photovoltaic films, window films, and countless other applications. Mayer rods are widely used as a pre-coater for board, as the method produces a smooth finish for final coating. With absorptive substrates, rod pressure is also a contributing factor in coating build.Īs applied, the coating flows through the cavities in a pattern of parallel stripes surface tension draws them together, providing a flat, smooth surface. Hardness of the backing roll cover, temperature, and line speed can also have minor effects. ![]() High viscosity and high solids content coatings will tend to reduce wet film thickness, especially at low coating weights. Wet film thickness is predominantly controlled by wire size, as the area of the cavities is directly proportional to the diameter of the wire the film thickness is roughly one tenth the diameter of the wire. The cavities formed between the wire coils meter the amount of coating which can pass through, and remain on the web. The concept behind metering rods is elegantly simple: An excess amount of coating is applied to the web, which is then metered by a stainless steel rod that is tightly wound with a spiral of stainless steel wire. Over time, a variety of innovations and improvements have been implemented for this technology, including the use of stainless, rather than cold-rolled, steel hard chrome plating for improved wear and the introduction of double wound, gapped, and formed rods for high viscosity and high solids content coatings. The machines demonstrated the superiority of Mayer's patented wire wound rods for applying such coatings. The company designed and built equipment for manufacturers of carbon and wax papers. Metering rods - also widely known as Mayer Rods, drawdown bars, or metering bars - were invented in 1905 by Charles Mayer, who founded the Mayer Coating Machines Company in Rochester, NY.
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