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The
EXTRUDER
TIMES
C A T A L Y S T
Through this column ET will cover briefly
relevant information on key components that
goes into an extruder
Barrel
The processing section of an extruder primarily consists of a set of barrels and the screw.
Conveying, mixing, kneading, melting, metering, etc. take place in the processing
section.
In a twin-screw extruder, two intersecting cylindrical bores in the shape of “8” form the
core of the barrel. The barrel houses the screw. It also serves as the primary heat transfer
medium in the process. It has to resist wear, overcome the process pressures, and oppose
screw torque.
Barrels are normally rectangular or cylindrical steel blocks with a flange at the feed-end
for mounting to the gearbox and another flange at the discharge end for mounting to
the adjacent barrel flange or the die system. The flanges will have through or threaded
holes for mounting purpose. In most cases high alloy steel liners are used as the core of
the barrel to resist wear and corrosion.
Courtesy: Mr A Vishwanathan, Director R&D, Steer Engineering
This article is contributed by Dr. Babu Padmanabhan,
Managing Director and Founder of Steer Engineering.
He is a PhD in Mechanical Engineering from Virginia
Polytechnic Institute and State University Blacksburg VA
STEER’s deep-flighted intake (SFV) elements (Fig. 3 patent pending) are specifically
designed to improve the conveying efficiency. At low screw speeds, these elements are
capable of compacting the material during conveying. Increase in intake capacity of
nearly 200% is achievable at RPM range of 150 – 900. The element responds to increase
in screw speed beyond this range in an unusual manner. With a 40 mm machine, it has
been experienced that increase in capacity was 300% of typical elements at 1100 RPM.
It is expected that the element creates a partial vacuum and can suck in the material from
the hopper and compact it while conveying.
SFV ELEMENTS
TO IMPROVE INTAKE CAPACITY AND BOOST OVERALL EFFICIENCY OF TSE
NEW
Continued...
An experiment (Fig. 4) carried out with a premix of 50% Talc and 50% LLDPE granules
reached torque limit at 900 RPM. Increase in screw speed resulted in linear increase in
capacity. With a different formulation containing 40% Talc, the suction effect was
observed at 1100 RPM and a sudden raise in starve-feeding capacity limited only by the
torque capacity of the extruder.
The SFV Elements are an integral part of some STEER TSEs, especially the OMEGA
Series of Extruders.
OUTPUT (kg/hr)
SCREW SPEED (RPM)
900
600
300
0
0
100
200
300
OUTPUT (SFV)
OUTPUT (SKE)
OUTPUT (RSE)
Fig 4: Performance of STEER’s SFV
Key advantages of SFV elements
• Converts feed-limited to torque-limited
utilizing the machine to a great extent
• Improves efficiency of processing by
lowering specific energy
• Side feeding can be avoided hence
reducing the equipment cost