Basic HTML Version
The
EXTRUDER
TIMES
MAY-JUNE 2006
VOL.01 / ISSUE-03
I N T H I S I S S U E :
Review:
SFV Elements
Fundamental Concepts of Compounding
Catalyst:
Barrel
ReCap:
Extrudate Swell
Brainstorm:
Maximum Torque Utilization
Question 4 You:
Side Feeder Ports
R E V I E W - 1
Introduction:
The earliest co-rotating twin-screw extruders had shallow flight depths
and were designed to be run with a filled-up hopper, in the same way an injection-
molding machine or a single-screw extruder is run. As the technology progressed and
flight depths increased, it became necessary to adopt a different approach to get the
material into the extruder. This approach is now popularly called starve-feeding. In this
approach, an additional feeder is used to provide a steady flow of material to the
extruder. The hopper is no longer a vessel to hold material but simply a chamber through
which material enters the extruder. In many cases, it can be seen that the extruder has a
large capacity for accepting such feed. If controls are not exercised, such situations can
stall or break the mechanical parts and the electrical drive system. Therefore, the limiting
factor is the torque availability. While feeding polymers devoid of any other filler, the
material feed rate is generally a fraction (0.05 – 0.20) of the volumetric capacity of the
extruder. Since there is very limited material in many zones of the extruder, the extruder
is considered to be “Starving”.
There are now many applications where fillers are added at very high percentages. Most
applications with Talc or extremely fine Carbon are difficult to process because of severe
limitation in intake capacity of the main extruder or the side-feeder. While many applica-
tions are torque-limited, these specific applications become feed-limited. A new element
called the SFV element can be used to greatly improve the intake capacity while starve-
feeding. These find application especially in the deep-flighted, high-speed extruders,
which can handle feed-limited applications the best.
A special initiative of
CONSULTANC Y SERV I CES , I ND I A
This issue of ET is sponsored by
Visit: http://www.steerit.net/products/outline.html
STEER’s
OUTL
·
NE
The Configuration Management Software
for Twin-Screw Extruders
• To share breakthroughs and happenings in the
Extruder Industry with special emphasis on
Twin/Single Screw Extruders.
• To serve as an information sharing platform for
STUDENTS, ENGINEERS and COMPOUNDERS.
• To generate triggers and encourage contributions
from scientists, technocrats and teaching
community for new innovations.
A IMS AND OB JECT IVES
3
SFV ELEMENTS
TO IMPROVE INTAKE CAPACITY AND BOOST OVERALL EFFICIENCY OF TSE
NEW
What is the profile of the intake elements?
The profile of the intake zone elements has an important role in the conveying efficiency
and capacity. Traditionally, profiles in the feed zones may be Normal Bi-lobed Right-hand
Screw Element (RSE) with spline bore with leads 1.0 to 1.5 times the diameter (Fig. 1).
Modified Right-hand Bilobed Elements called SchubKanten Element (SKE) have 20%
more free volume and provide corresponding improvement in capacity (Fig. 2).
Fig 1: RSE
Fig 2: SKE
Fig 3: SFV
Continued...