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The
EXTRUDER
TIMES
Published by
CONSULTANC Y SERV I CES , I ND I A
What are the factors influencing the maximum torque utilization in co-rotating
twin-screw extruder?
- Rajendra Prasad, Bangalore
To utilize the machine, the extruder has to be fed with sufficient quantity of material.
There are a few factors that affect the utilization of an extruder to its full extent. These
can be divided into restrictions at the Upstream (material cannot be fed), Mid-stream
(material comes out through the vent) and Down-stream (required die/screen pressure
for material to exit)
In general, the higher the torque utilization in the extruder, the more efficient is the
process. At any given screw speed, if the applications is run at the maximum available
torque, this means that full available motor power is being utilized. In co-rotating twin-
screw extruders that are controlled by torque, full motor power is available at the
maximum screw speed.
1. Variation in Feeding -
Material is fed into the extruder using an additional feeder. In
the case of most volumetric feeders and some gravimetric feeders, this feeding is not at
a steady rate. This leads to variation in the torque levels in the machine. It is necessary to
set the feed such that the maximum value will not trip the machine. If the variation is
high (10%), then the machine will be under utilized.
2. Feed-limitation -
There are certain materials that will easily flood the extruder hopper.
Since the entry of material is limited, this restricts the torque utilization.
3. Availability of side-feeders -
In many cases, feed-limitation can be overcome by the
use of side-feeders utilizing the full capacity of the machine. However, many extruders
do not have additional side-feeders causing limitations in usage of the machine.
4. Leakage from the Vent / Metering capacity -
In many applications, the leakage at
the vent restricts utilization of the machine. Proper choice of inserts and design of screw
configuration are important aspects to avoid leakage at the die.
5. High Die-head Pressure -
Extruders are built to withstand a certain die-head
pressure. The pressure increases with usage of screens. Certain highly viscous materials
develop high die head pressure limiting the output of the extruder.
- Babu Padmanabhan
on behalf of ET expert panel.
For further queries on the subject you may write to: drbabu@steerworld.com.
Brainstorm
Reader's Queries on Extruders, Elements,
Polymer-Compounding etc are answered
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QUALIT Y PRIORITIES
S
PEED -
how time-critical is this?
P
ERSONAL TOUCH -
how important is it to manage
the customer's state of mind?
A
CCURACY -
how important is precision, confor-
mance to specifications, safety, security, informa-
tion clarity, and error prevention?
C
OOPERATION -
how important is it to dovetail
with another person's task or with what the
customer is doing?
E
CONOMY -
how important is it to minimize the
resource cost involved?
“SPACE”
is the acronym for the above. It may not
completely cover all aspects, but helps focus
energies.
- Karl Albrecht
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errors or omissions and accept no responsibility for any loss or damage caused as an effect thereof. The opinions
expressed by experts are their own and in no way reflect that of the publisher.
Printed and Published by: ET editorial coordinator KSRam on behalf of STEER CONSULTANCY SERVICES, 290, 4th
main, 4th phase, Peenya Ind. Area, Bangalore - 560 058, India.
etec@steerworld.com
FOR PRIVATE CIRCULATION ONLY
Technical Contributions Most Welcome!
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tions and extruder technology project /
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Please send your contributions to
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How many side-feeder ports can be
configured in a 40 L/D Co-rotating
Twin-screw Extruder?
The best answer will be published in subsequent ET
with name and photograph of the reader. Readers
are INVITED to send-in their answers with/without
drawings/pictures/illustrations to
etec@steerworld.com
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NPE
2006
NPE Society of the Plastics Industry Inc.
Mc Cormick Place, Chicago, IL USA