Screws & barrels | machinery feature
Screw redesign can help to boost the output and effi ciency of extrusion machines. Lou Reade reports
Performance boost
The sheer power of an extruder – such as the design of its motor and gearbox – is often taken to be the main contributor to its power and effi ciency. But designing (or redesigning) the screw can also be a huge factor in squeezing more performance from a piece of machinery. A redesigned screw is at the heart of the new KME 60-41 B/R single-screw extruder series from Krauss- Maffei Berstorff. With an actual processing length of 41L/D, the series is aimed at high-performance PE and PP pipe extrusion. “When we were redeveloping this series, we
incorporated elements from our 36D series, and combined these elements with a new processing concept,” said Peter Roos, president of KraussMaffei Berstorff. “The new series, with its patented processing concept and 41L/D screw, delivers a disproportionately increased throughput, while maintaining low melt temperatures and high product quality.” The redesigned screw is designed to use its entire
length for melting and homogenising. This reduces the amount of stress on the polymer, as well as ensuring that plasticisation has less effect on material properties during the melting process. At the same time, an improved combination of heating and cooling allows the barrel to ensure optimal heat dissipation. A fi lling opening – which has been modifi ed in terms of length and dimensions to accom- modate the increased throughput – ensures linear throughput development across the entire speed range, says the company.
www.pipeandprofi
le.com The design of the spiral grooved bush provides
low-impact material handling and feed stability. Long machine life is implicit in the new extruder series, with bi-metal barrels and optionally through-hardened grooved bushes imparting highly wear-resistant properties.
The 41D series is available with 45, 60, 75, 90, 105 and 125mm screw diameters.
Better barrel The ConEx series of conical twin-screw extruders from Battenfeld-Cincinnati also benefi t from redesigned screws, as well as an improved barrel design. The four models in the series, ranging from 38 to 72mm screw diameter, are around 10% more produc- tive than previous generation models, thanks to an optimised screw geometry, says the company. This applies to pipes at outputs up to 550kg/h, and profi les up to 280kg/h. Long service life is ensured by a molybdenum screw
coating, which the company says is unique in the industry. The complete width of the screw fl ights is covered with a very pure layer of molybdenum, to protect it from wear. At the same time, energy effi ciency has been boosted
thanks to a complete barrel insulation system. It includes the proven barrel insulation in the feed and degassing zones plus, as a novelty: thermal separation between the metering unit and the barrel feed opening by means of an insulating plate.
March/April 2014 | PIPE & PROFILE EXTRUSION 23
KraussMaffei Berstorff’s KME 60-41 B/R single-screw extruder
benefi ts from a redesigned screw
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