Praxair Surface Technologies Inc., which uses a thermal spray technology to wear-coat screws and barrels, knives and chill rolls, is moving into a new area — flat dies for making cast film.
The Indianapolis-based company runs 27 plants throughout the world that do the coating. For screws, the company applies highly wear-resistant tungsten carbide coating to the entire screw profile, or just the tops of the flights.
To coat screws, Praxair uses a detonation gun coating process. The coating material, in powder form, is metered into the barrel of the gun and combined with a mixture of gases. The gas mixture is detonated with an electrical spark, heating and blasting the powder down the barrel. The coating is propelled at supersonic speeds onto the part being coated, where it forms a dense, uniform coating with a tight bond.
The coating material can be tungsten carbide, tungsten carbide cobalt and tungsten carbide nickel chrome.
Praxair uses various coating services, including thermal spray, vapor deposition, electro deposition and laser processing.
Coating the lips of flat dies is a new market, although Fred Paonessa, senior market development specialist, said Praxair already serves the film and sheet industry by coating slitter blades, chill rolls and calender rolls.
During cast film processing, plastic builds up on the edge of the flat die. Operators have to clean the edge, cutting into production.
The Praxair coating can keep the edge very sharp. “To reduce polymer buildup, we've put tungsten carbide on it,” Paonessa said. Dies coated by Praxair are running in Japan, he said during an interview at Plastics News in Akron.
Praxair is working with flat-die maker Extrusion Dies Industries LLC of Chippewa Falls, Wis.
Paonessa works out of the Praxair facility in Canton, Ohio.
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