machinery | Wear protection
Right: Feddem’s HIP barrel elements feature a 3-5mm thick abrasion resistant
powder metal internal coating
which has been part of the CPM Extrusion Group since January of this year. “We also offer high performance T-Profile elements, which improve mixing efficiency while the overall energy input is reduced and this has a positive effect on abrasive wear.” In addition, the company has
developed one-piece elements that are said to provide more homogeneous torque transmission in screw areas where mixing and flow restrictive elements are combined. The one-piece element reduces the probability that any corrosive material can leak between the front surfaces to the shaft, which could lead to corrosive damage to the shaft. Furthermore, the tight fit and extended length of the shaft-hub connection is said to reduce corrosive pitting and fretting and ultimately leads to more flexural resistant shafts. Manufactured using either a through-hardened
material or with cladded wear protection, CPM’s Thinlin- er technology allows worn barrels to be refurbished. Previously, the company says this was not possible, which made dealing with wear a costly exercise. Looking further ahead, wear reduction initiatives are likely to centre on Industry 4.0 technologies that will enable evaluation of the wear situation in real time through the use of intelligent sensors. The target will be to maxim- ise service life without sacrificing reliability. Coperion has also been examining high wear
production applications and developing wear and corrosion protection coatings and cladding. “There is a trend towards extreme abrasive wear and the need for wear and corrosion protection for applications such as highly filled engineering plastics,” says Karl-Conrad Polzer, a specialist in the company’s Development
Right: Screw
element wear is influenced by many factors, including screw configuration,
element design and feed options
Materials Department. “Higher wear and corrosion
protection with high damage tolerance continue to be required in extruder screws and barrels, although it is important to maintain the balance between the manufac- turing process and finished granulate/product costs. Other
compounding trends involve increased specific torque, higher throughputs and rotational
speeds,” Polzer says. “Combined with new polymer developments including recycled and highly filled engineering plastics, this is leading to increased wear phenomena and specifically highly developed wear in certain areas. This results in a loss of productivity, increased downtime and maintenance costs. Specific problems arise in the melting section and pressure build-up zone.” Construction material is not the only factor that
needs to be considered when assessing wear. “Com- pounding machines have to be seen as a wear system that could be influenced by machine design, screw configuration, as well as screw element diameter providing screw distortion and adhesive wear,” says Franziska Hagel, who also works in the Coperion Development Materials Department. “Wear can be reduced by optimised screw configura-
tion, for example by feeding of abrasive fillers into the melt and not into the main feed to reduce wear in the melting section. In addition, low process temperatures in combination with optimised screw design can avoid degradation and the release of corrosive volatiles. Operating conditions, such as cleaning, ramp up and shut down conditions, and handling are also all factors. However, frequently it is necessary to take measures to prevent wear and machine damage and a subsequent negative influence on the product quality,” Hagel says. To meet these requirements, Coperion offers its Diamond barrels and liners. These use a new material comprised of tungsten carbide embedded in a NiCrBSi- based matrix. Properties include good wear and corrosion resistance. Applications include the barrels of the melting section and pressure build-up zone, particularly for systems processing engineering plastics, as well as other areas faced with high abrasive wear. The company says customer trials in different industries have shown the Diamond material provides ten times better protection than comparable materials in highly abrasive processes. Extruder manufacturer Feddem offers a number of
options for screw and barrel protection. “As well as special alloy solutions, we now also have a good
66 COMPOUNDING WORLD | August 2017
www.compoundingworld.com
PHOTO: FEDDEM
PHOTO: COPERION
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