Twin-screw extruders | machinery feature Twin-screw extruder makers are busy launching lots of new
machinery at this year’s big plastics exhibitions. Peter Mapleston reviews the latest developments and picks out some key trends
turn up the torque
The international exhibition season is in full fl ow. PlastIndia kicked things off in February, while NPE is taking place in the USA this month and will be followed by Plast in Italy in early May and then Chinaplas later the same month. Many machine makers are unveiling new developments at these big events, and twin-screw co-rotating extruder manufacturers are no exception. Not for the fi rst time, torque is at the centre of numer- ous discussions. The next generation of Coperion’s STS twin-screw
extruder is making its world public debut at Chinaplas 2015 in May. STS Mc11
models have more torque than
their predecessors – 11.3 Nm/cm³, up from 10.0 – and are the fi rst STS types to make use of technology covered by a patent that Coperion holds on high-speed, high-torque intermeshing twin-screw extruders, and which has been used for many years on its ZSK Mega compounders. The patent (which runs out in the middle of next year) means that only Coperion can supply extruders with the combination of an OD:ID ratio of between 1.5 and 1.6, screw speed of over 800 rpm, and torque density (screw torque divided by the cube of the centre-to-centre distance) of over 11 Nm/cm3
. The STS Mc11 extruders have screw diameters ranging from 35 to 96 mm.
www.compoundingworld.com
Output from the new units is 27% higher than before, but the higher degree of fi ll means that melt tempera- ture can be reduced, so the quality of the compound is improved. Screw speed has been increased from 800 to 900 rpm. Coperion says that the STS Mc11
series is
equipped with the same European gearboxes that have already been proven on its ZSK machines. The STS Mc11
has new hoppers with inserts and a
redesigned die head, intended to improve cleaning and speed up changes for masterbatch applications. The screw shaft coupling is similar to that on the ZSK Mc18 series. To increase stiffness for handling the increased torque, the STS Mc11
series has a new base frame,
totally redesigned using FEM (fi nite element method) to dampen vibrations and deliver smooth running. Coperion says that it also increases operational safety and ensures long service life of the extrusion system. The STS series is produced by Coperion at its facility in Nanjing, China. The company says that it has “undertaken comprehensive initiatives” to improve quality standards there. The operation is now equipped with state-of-the-art German machining centres and uses the same production norms as in Europe. The production process is said to be very closely monitored,
March 2015 | COMPOUNDING WORLD 31
Twin-screws
Sneak preview: Coperion’s
brand new STS Mc11 twin-
screw extruder will make its
world debut at Chinaplas in May
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