Basic HTML Version
The
EXTRUDER
TIMES
JULY-AUGUST 2006
VOL.01 / ISSUE-04
I N T H I S I S S U E :
Review:
Configuration of Screw Elements in EPZ!
Brainstorm:
PVC Compounded in Counter-TSE
Question 4 You:
Shear, Shear Rate, and Shear Heating
Introduction:
The adage ‘different strokes for different folks’ holds good when one
attempts to deal with the EPZ (
Extruder Processing Zones
) of a Co-rotating Twin-Screw
Extruder. Within this EPZ area the ‘key to success’ lies with the exact design of the
‘Element and Barrel’ Configuration. In the game of Chess, a ‘good formation’ is impor-
tant to achieve a winning result, since pieces in isolation cannot perform. This is true in
the case of Compounding. Elements work best in some combinations, and some
elements are more powerful than others. Indeed, it is true!
Importantly,
1. The design has to deliver the correct amount of work on the
product for melting and mixing.
2. The design should have the capacity to take the product
“in” and “out” of the extruder.
3. Lastly, the design should allow gases or volatiles to
escape without the product leaking out through vents.
It can be imagined that there are
‘different zones’
(area) inside the extruder performing
a series of specific functions
1
. Like a relay race, each zone passes on the ‘baton’ (the
material being processed) to the next zone and until the final stage. Extruder perfor-
mance measured by energy consumption, quantity and quality of output, largely
depends on the design of these processing zones. The effective selection of elements is
the first step in design. The right length and combination of elements is the next step.
In this 6-article series (beginning with ET#4) we shall discuss these various zones and
outline the element characteristics, its potential use and certain design principles. The
first set of three articles will focus on the selection of elements based on their innate
characteristics. The second set of three articles will provide the design principles for
combining or configuring these elements for different applications.
ELEMENTS for various PROCESSING ZONES
These processing zones make up the “Race-track” of a Twin Screw Co-rotating Extruder.
Intake Zone
— for introducing the material into the extruder.
Melting Zone
— for heating the material and therefore melting the material
and achieve partial or total mixing.
Venting Zone
— for removing the volatiles & moisture.
Mixing Zone
— for ensuring proper mixing.
Vacuum Zone
— for completely removing the volatiles & moisture to the
(Venting Zone)
required levels.
Metering Zone
— for building up the required pressure at the die.
(Note: Other zones such as side feeding, liquid dosing etc., are not included in this article.)
A special initiative of
CONSULTANC Y SERV I CES , I ND I A
4
Continued...
CONFIGURATION OF
SCREW ELEMENTS IN
EPZ!
A N O V E R V I E W
• 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 JEC T I VES
INTAKE
ZONE
MELTING
ZONE
VENTING
ZONE
MIXING
ZONE
VACCUM
[VENTING] ZONE
METERING
ZONE
This issue of ET is sponsored by
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