machinery feature | Twin-screw extruders
This analyses the inputs from key points in the system, makes numerical calculations, and applies corrections to the extruder screw RPM and feed rate to maintain the gear pump inlet pressure at a given set point. With its new TEM-58SSG, Toshiba says that it wants
Steer’s Omega extruder is the basis for its CMGFT process technology
to improve yields for compound makers by boosting the basic capabilities of previous machines at a competitive price. It says that the unit strikes a balance between industry-vital features and cost. It can use the same screw elements as the original TEM-SS series, but has a new high-rigidity barrel and is offered with high- toughness screw elements.
Other key features include expanded feed capabilities with a wide-aperture feed barrel (67% bigger than before); and a low-pressure-loss/high-filtration-area breaker plate and small orifice plate. A high-rigidity frame and levelling plate simplifies machine installation. In addition, a special coupling option makes screw
installation/removal easier, and special plates at the base of the feed barrel can also be fitted on request to facilitate maintenance. The vent port is also easier to clean, thanks to a new vent clamp system instead of the previous bolt-based installation. There are also various options to improve wear
resistance, including the AW2-6B anti-wear screw element (the external layer is in a specialized steel, and the core layer is an undisclosed high-toughness material), a sleeve-type barrel, and ceramic orifice plate.
Taking care of fibres
Steer announced at PlastIndia that it has developed a new process to produce what it calls Continuous Medium Glass Fiber Thermoplastics (CMGFT) on its flagship Omega twin-screw extruders, using its Frac- tional Lobe screw geometry. The process leverages the specialized functionalities of various screw elements, such as RFV (for intake), FKB (for melting of polypropylene); and the OSE wave element (for wetting of glass fibre). Compounding is carried out on a high-flight-depth, high- free-volume Omega unit. Steer says CMGFT is best for applications where PP and polyamide short-glass-reinforced materials are normally used. “For example, CMGFT PP with 30% glass is better than PP 40% short-glass-filled grade in terms of cost and lightness,” it claims. The company says that CMGFT is a cost-effective alternative that can be used for automotive engine compartment parts like radiator end-caps, fan and shroud assemblies, and air intake manifolds. Maris meanwhile emphasizes its own expertise in technology for
producing glass-fibre-reinforced compounds. It points out that screw design has a significant impact on the properties of the final compound – a low-shear screw can produce an average fibre length well over 25% higher than a higher-shear screw, with significant implications for stiffness, strength and impact resistance in the finished material. It also says that the judicious use of coupling agents – sometimes more than one in the same compound – is particularly important when it comes to impact resistance. ❙
www.steerworld.com ❙
www.mariscorp.com
42 COMPOUNDING WORLD | March 2015
Future-proof The ZE BluePower is described by supplier KraussMaf- fei Berstorff as a “future-proof” twin-screw extruder series. It has a Do/Di ratio of 1.65 and a torque density of 16.0 Nm/cm3
. “The hydraulic screw preloading
system, oval liners for high wear protection, improved side feeders, degassing systems and energy manage- ment tool provide substantial benefits”, says Thomas Winkelmann, head of plastics technology development. The ZE BluePower series is currently available with
screw diameters of 42, 52, 65, and 80 mm. It will completely replace the ZE-UTX twin-screw extruder series in the medium term. As reported in previous issues of Compounding
World, the ZE BluePower combines increased torque density with an enlarged volume compared with the previous generation. Torque density is over 30% higher for torque-limited processes, while the volume is more than 23% higher for volume-limited applications. The company says that theoretical calculations and actual trials have shown that the best results are achieved at a Do/Di ratio of 1.65 and a torque density of 16.0 Nm/cm3
. As well as using powerful drive units, high-resist-
ance screw shaft materials and optimum tooth profiles at the screw shafts, KraussMaffei Berstorff has also developed a preloading system that ensures reproduc- ible screw installation and preloading. It subjects the screw shafts to a defined tensile stress only, without exerting any torsion load. “The machine operator simply selects the appropri-
ate pressure specified in the machine documentation and clamps the extracted screw in the preloading system,” says Winkelmann. “At the push of a button, the combination of screw shaft, screw element and screw tip is preloaded in the elastic range and in this state can
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