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An air knife is a cleaning, drying and cooling device used in manufacturing and other processes. By creating a high intensity, balanced sheet of laminar airflow across the entire length of an object, an air knife can clean, dry or cool components, webs and conveyors. Laminar airflow refers to a uniform layer airflow that doesn't mix with the other layers nearby. Air knives come in two types, linear and circular, and can be made out of aluminum, steel or plastic.
An example of an air knife is the high-pressure air-blasting device used at the neighborhood car wash to remove any water, oil and dirt residue from a washed car.
Historically, a heat lamp dryer, the alternative to the air knife, was used to remove water particles. The heat lamp dryer however didn't remove solid phase residue completely and took up more time and space. An air knife, on the the other hand, takes less time, occupies less space and most importantly dries components completely.
But drying is only one of the various functions an air knife performs. The array of manufacturing uses of air knives is bewildering. Typically air knives are used for cleaning, drying and cooling any type of surface ranging from cans and bottles to textiles and printed circuit boards.
In conveying systems air knives are used on continuously produced parts or products. For instance in the cement industry air knives can be used to remove dust and gravel from the conveyor. In the case of a high tech product like printed circuit boards that go through many chemical baths during production, air knives speed up the production process by drying the printed circuit boards after each chemical bath. Rubber extrusion used in making seals for car doors and windows require a dip in hot salt potassium nitrate to give it a gloss. An air knife can be used to blow off the excess salt to restore the gloss.
An air knife can also be used to remove viscous contaminants from a surface. Cutting oil used in the production of threaded metal rods can be blown away by an air knife..
Apart from regular industrial uses, air knives have other uses. Cushioning two sheets of paper or steel and preventing friction between the layers, acting as air curtain to prevent mixing of two types of air, and blowing soil away from roots for inspection are some of the other uses of an air knife. Air knives are available in various sizes. A three foot (0.91 meters) long air knife unit may cost anywhere between $500 and $3000 US dollars (USD) depending on functionality.