Nordson’s Xaloy MPX
machinery feature | Screws & barrels This is done with an outer shell of VSA4 material
thermal spray coating
deposits tiny tungsten carbide
spheres onto screw surfaces
surrounding an inner core of more resilient steel. This screw element metallurgy, in conjunction with the VSA4 barrel metallurgy, claims to protect against most processing tasks. Meanwhile, India-based Steer says that its Micro-
genic Technology has allowed it to extend the wear performance of extrusion screws – such as Acrolloy 55, the latest in its range of tool steels. The material is rich in vanadium, and also contains other alloying and micro-alloying elements that combine to give strong abrasion resistance. The uniformly distributed carbides, metallically
bonded to the matrix, exceed the wear properties of traditional HIP powder metallurgy steels “by a large margin”, according to Thiru Arumugam, head of the company’s tool steel operations. The material also offers a good combination of red (or hot) hardness, toughness, wear resistance and cutting ability, along with fine grain and carbide particle size. Steer says that it offers superior properties – in both a bromine and abrasion environment – to AISI M2, the current top choice for flame retardant applications.
Tiny spheres Nordson has developed a technology that uses tiny tungsten carbide spheres to coat single and twin plasticating screws – giving them greater resistance to abrasive and corrosive wear than standard coatings applied by high-velocity oxygen fuel (HVOF) thermal spray. Its Xaloy MPX thermal spray coating is made up of
particles only 5 microns in diameter. Consisting primarily of tungsten carbide, the particles are six to seven times smaller than those in standard HVOF coatings and more densely packed, owing to a uniform spherical shape produced in a controlled plasma process. The combination of ultra-fine particle size, higher coating density, and a 2.5 times greater applica- tion velocity results in a stronger bond with the parent metal of the screw and improved resistance to wear, says the company. Compared with standard HVOF tungsten carbide
coatings, the technology exhibits 61% less mass loss in ASTM G65 abrasion testing. As an example of its corrosion resistance, the coating survived more than 1,000 hours of salt fog testing, in part because of its near-zero porosity. “This screw coating provides best-in-class wear
protection compared with standard HVOF coatings, and its higher bond strength eliminates potential for chipping,” said Mark Colella, global product manager for the Xaloy brand. “This technology extends the working life of screws, enabling processors to work with
40 PIPE & PROFILE EXTRUSION | March 2017
some of today’s most challenging materials.” Nordson recommends the Xaloy MPX technology for
resisting abrasion from compounds with medium (15 to 35%) filler loadings and for resisting corrosion from halogenated materials, including flame retardants and PVC. For filler content above 35%, Nordson supplies the high-hardness coating Xaloy X-8000.
All change Nordson is to combine its existing screw and barrel operations in Youngstown in Ohio, New Castle in Pennsylvania, and Pulaski in Virginia into a single expanded ‘manufacturing centre of excellence’ at Austintown in Ohio. Nordson said the process will take up to 18 months and is subject to the conclusion of negotiations with local and state officials. The company said it will invest in upgraded bi-metallic processing and machining systems at the new facility and will move most of the jobs from the existing three. In all about 260 people are expected to work at Austintown. The creation of the new manufacturing facility
mirrors other regional hubs established by Nordson in Germany and Thailand as the company seeks to “drive efficiencies in manufacturing processes, decrease lead times, enhance customer service, improve competitive- ness and accelerate growth,” according to corporate senior vice president John Keane. “No other single supplier will be able to provide the polymer industry with such localised service on a global scale,” he added.
Click on the links for more information: ❙
www.ejs-screwbarrel.com ❙
www.extremecoatings.net ❙
www.leistritz.com ❙
www.steerworld.com ❙
www.nordson.com
www.pipeandprofile.com
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