1. An experimental study compared the performance of an extruder with a single-piece barrel and integral feedport design to a standard two-piece barrel configuration. 2. Testing was conducted using two resins (HDPE and PP) across a range of screw speeds. 3. Results showed the integral design produced higher output rates and melt temperatures for both resins compared to the standard configuration, with a more significant increase seen for PP. 4. The integral design improved solids conveying by increasing heat transfer to the feed zone, raising temperatures and the coefficient of friction between pellets and barrel wall.

1. AN EXPERIMENTAL INVESTIGATION INTO SOLIDS FEEDING
CHARACTERISTICS OF A SINGLE PIECE BARREL WITH INTEGRAL FEEDPORT
DESIGN VS A STANDARD TWO PIECE WATER COOLED FEEDBLOCK AND
BARREL CONFIGURATION.
Walter S. Smith
Robert A. Sickles
Luke A. Miller
Timothy W. Womer
Xaloy Corporation, New Castle, PA
Abstract L/D along its axial length. Figure 3 shows the integral feed
block configuration.
Differences in solids conveying, screw pressure profile
generation, output and melt temperature varies between Figure 4 shows the 711mm (28”) Flex-lip Sheet die and the
single piece barrel with integral feedport design and two Slide plate screen changer. The die was set to 1.4 mm
piece water cooled feedblock and barrel designs. Two (.055”). The Screen Changer was loaded with a breaker
different resins will be studied using the same screw plate and a 20/40/60/20 screen pack. A immersion melt
design for each barrel configuration. probe was inserted in the melt stream between the screen
changer and die.
Introduction A low shear barrier screw with mixer was used for all
testing. This screw was specifically designed for
Extruders can be designed with either a standard two- polypropylene extrusion with a longer feed section.
piece water-cooled feedblock- barrel configuration, or
with an integral feed port - thru barrel configuration. This A Fluke Data Acquisition System was used to acquire all
paper will explore the processing differences between data from the process. It will be referred to as NetDAQ.
these two different barrel configurations under the same
controlled processing conditions and equipment. Resins
Equipment Two resins were used for this study.
• 100 % HDPE Regrind (540 kg/m3 bulk density)
The extruder used for this study was a 90mm (3.5”) x 0.3 MI
24:1 NRM Extruder with five-barrel water-cooled • 100 % PP Regrind (384 kg/m3 bulk density) 2.0
temperature zones. It is equipped with a 112 kW (150 MI
Hp) DC motor. Max screw speed is 129 rpm. Figure 1
shows the extruder with (11) melt pressure transducers
located every 2 L/D down the axial length of the barrel. Experimental Procedure
The standard two-piece configuration consisted of a
Each of the two resins was extruded using the integral feed
separate water-cooled feedblock with a flanged extrusion
port, with water cooled feed block; and the standard two-
barrel bolted on the downstream end of the feed block.
piece ductile iron water-cooled feed block for a total of four
This barrel also has (11) melt transducers to record the
twenty-seven minute runs.
internal pressures at every (2) L/D along the axial length
of the barrel. Figure 2 shows the barrel feedblock
For each test, the barrel and screw were completely cleaned.
configuration.
The die was pre-heated two hours prior to each twenty-
seven minute test, and the barrel was pre-heated to
The integral configuration consisted of an extrusion barrel
processing temperature for one hour before the testing
that fits through a water-cooled feed block with a feed
started. Steady thermal conditions were then assumed to
port machine directly into the cylinder. This barrel also
prevail throughout each of the four twenty-seven minute
has (11) melt pressure transducers located at every (2)
tests.

2. amp draw at all (5) screw speeds for both barrel
The two resins were run on the standard two-piece configurations running HDPE. Again, the increase in motor
feedblock and barrel configuration. The feedblock was load is directly attributed to the increase in throughput rate.
water-cooled. Once these trials were completed the barrel
and feedblock were changed to the single piece barrel The barrel pressure profiles for both screws running HDPE
with integral feedport. The same “hump” barrel at 125 screw rpm on both barrel configurations are shown in
temperature profiles were used for same barrel type and Figure 12.
resin tested along with the same feed throat water
temperature. See Chart 1 for barrel temperature profiles. The integral feed port configuration produced both higher
rates and melt temperatures for running HDPE. See Figure
Each test included screw speeds of 25, 50, 75, 100, and 13 for an output/melt temperature comparison. The
125 rpm. Melt temperature was checked at each screw temperature of the integral barrel, in the area under the feed
rpm using a hand held IR gun, melt probe, and immersion zone was also measured and recorded at all (5) screw
probe. Three one-minute sheet samples were taken at each speeds. See figure 14 for a screw rpm vs. feed zone
set rpm to calculate screw output rate. The barrel temperature graph.
pressure, immersion probe, screw speed and motor amps
were all monitored and recorded at one-second intervals Discussion of Data and Results
on the NetDAQ.
The data were then extracted from the NetDAQ and The major difference between the (2) machine
compiled with a spreadsheet program. configurations is the thermal isolation of the feed port in the
standard (2) piece configuration. Heat from the barrel does
Presentation of Data and Results not travel as easily back to the first (2) turns of the feed port
area in the standard two-piece configuration. Both barrel
Regarding the PP trials: The integral feed throat pressure profiles, for HDPE and PP; confirm that the screw
configuration produced more output at every screw speed, builds higher pressure much earlier in the feed section of the
than the standard two piece barrel and feed block screw. This higher-pressure buildup can be attributed to
configuration. The output increased across all screw more resin melting and a higher coefficient of friction
speeds for the integral configuration. See Figure 5 for between the pellet and the barrel is causing the resin to stick
output rates for the (5) screw speeds comparing the (2) to the barrel sooner and improve solids conveying. This
barrel configurations. As suspected, the amp draw was up extra heat in the feed port area migrating back from the first
at all (5) screw speeds on the integral configuration barrel zone; increases the coefficient of friction between the
compared to the standard (2) piece configuration, because resins an internal diameter of the barrel, thus enhancing the
of the increase in output. See Figure 6 for the motor amp solids conveying capacity of the screw. This is the main
draw at the all (5) screw speeds for both barrel reason for the increase in output of both of the screws and
configurations for running PP. both of the resins in the integral feed throat machine
configuration versus the standard configuration.
The barrel pressure profiles for PP at 125 Screw rpm on
both configurations are shown in Figure 7. The temperature range of the feed port area in the integral
PP trials was 69 C thru 62.5 C, versus a constant 22 C for
The integral feed port configurations produced both the standard (2) piece machine configuration. This recorded
higher rates and higher melt temperatures for running PP. temperature range depended on the screw speed. The faster
See Figure 8 for an output vs. melt temperature the screw rotated, the lower the recorded temperature in the
comparison. The temperature of the integral barrel, in the feed port area fell. The recorded temperature range of the
area under the feed zone was also measured and recorded feed port area in the integral HDPE trials was 71 C thru 59
at all (5) screw speeds. See Figure 9 for a screw rpm vs. C, versus a constant 22 C for the standard (2) piece
feed zone temperature graph. configuration. This recorded temperature range also
depended on the screw speed. The faster the screw speed,
Regarding the HDPE trials: The integral feed throat the lower the recorded temperature of the feed port area fell.
configuration produced more output rate at every screw It can be assumed at greater screw speeds, more room
speed, than the standard two piece barrel and feed block temperature resin goes thru this area, pulling more excess
configuration. The output increased across all the screw heat out, and thus reducing the barrel temperature in this
speeds for the integral configuration. See Figure 10 for critical processing area.
output rates for the (5) screw speeds comparing the (2)
barrel configurations. The amp draw was also up at all (5) The effect of the higher temperatures feed port area, in the
screw speeds for the integral configuration compared to integral machine configuration; had a much greater
the standard configuration. See Figure 11 for the motor influence on the output of each screw, especially when

3. running the PP. There was a 19.47% - 6.91% increase in Z1 Z2 Z3 Z4 Z5 S/C AD D1 D2 D3
output in the PP trials, depending on screw speed; as HDPE 380 450 440 420 400 400 430 430 430 430
compared to a 7.63% - 3.72% increase in output in the PP 400 470 450 430 410 410 430 430 430 430
HDPE trials.
Chart 1-Processing Temperatures
Conclusions
1. Heat migration using an integral barrel-feed port
barrel configuration will aid in solids conveying
and increased output in the extrusion process,
because of the increase in coefficient of friction
between the pellet and the barrel wall in the feed
section of the screw.
2. The increase in output in this study, attributed to
the integral barrel configuration; is more
pronounced when running PP and opposed to
HDPE.
3. Care must be taken when designing for an
integral barrel configuration, because of the
excess power required from the motor resulting
from the increase in solids conveying and screw
output.
Figure 1-90mm x 24:1 NRM Extruder
4. Although the higher temperatures in the integral
barrel configuration aid in solids conveying;
temperatures over 90 C should be avoided to
prevent resin from melting in the hopper
producing a melt block or bridging situation.
5. Modified barrel temperature profiles may be
needed to improve the overall melt temperature
of the process, which was not evaluated in this Figure 2-90mm Barrel Feedblock Configuration
study.
6. Integral feed throats improve alignment between
the barrel and gearbox, because one connection
point has been eliminated.
7. Venting of integral feedthroat barrels is more
difficult due to the improved solids conveying
that occurs. Additional testing will be done on
this subject and reported at a later date.
Figure 3-90mm Integral Feedblock Configuration
References
1. C. Rauwendaal, Polymer Extrusion, Hanser
Publishers, NY, 1986
2. E. Steward; W. A. Kramer, Air vs. Water Cooled
Single Screw Extruders, ANTEC 2003
3. J. Wortberg; T. Schroer, Novel Barrel Heating
with Natural Gas, ANTEC 2003

4. Integral Feedblock Compared to The Standard Feedblock on
PP+EVOH
Screen Changer 16000
14000
12000
10000
Pressure (KPa)
8000
6000
4000 Integral
Standard
2000
Die
0
0 57 71 92 108 128 144 164 181 199 221 240
Pressure Transducer Location from Face of Drive Shaft (cm)
Figure 7-Barrel Pressure of PP at 125RPM
Figure 4-Die, Screen Changer
Effect of Rate on Melt Temperature on PP
Output (Kg/Hr) of PP
200 255
200.00 25% Integral Rate Standard Rate Integral Melt Temp Standard Melt Temp
Integral Rate Standard Rate Rate 180 250
180.00
160
245
160.00 20%
19.47%
140
140.00 240
K g/H R (B ar G rap h)
°C (Line G raph )
Rate Difference
14.98% 120
120.00 15%
235
Kg/Hr
100
100.00
230
80.00 10% 80
225
60.00 7.16% 6.91% 60
5.25%
220
40.00 5% 40
20.00 20 215
0.00 0%
0 210
25 50 75 100 125
25 50 75 100 125
RPM
RPM
Figure 5-Output of PP
Figure 8-Effect of Rate on Melt Temperature
on PP
Effect of Rate on Amps Using PP
Temperature of Feed Zone on the Integral Barrel PP
200 100
Integral Rate Standard Rate Integral Amps Standard Amps
180 90
69
68
160 80
67
140 70
A m p s (L in e G rap h)
K g/H r (B ar G rap h)
66
120 60
65
100 50
°C
64
80 40
63
60 30
62
40 20
61
20 10
60
0 0
25 50 75 100 125 59
RPM 25 50 75 100 125
RPM
Figure 6-Effect of Rate on Amps-PP Figure 9-Temperature of Feed on Integral
Barrel-PP

5. Output (Kg/Hr) of HDPE Effect of Rate on Melt Temperature on HDPE
240 250
250.00 9% Integral Rate Standard Rate Integral Melt Temp Standard Melt Temp
Integral Rate Standard Rate Rate 220
245
8% 200
7.63% 240
200.00 180
7%
235
160
Kg/HR (Bar Graph)
6%
°C (Line Graph)
5.53%
R ate Difference
230
140
150.00
5%
K g/H r
3.93% 120 225
4.33%
3.72% 4% 100
220
100.00
80
3% 215
60
2% 210
50.00 40
1% 205
20
0 200
0.00 0%
25 50 75 100 125
25 50 75 100 125
RPM
RPM
Figure 13-Effect of Rate on Melt
Figure 10-Output of HDPE
Temperature on HDPE
Effect of Rate on Amps Using HDPE
Temperature of Feed Zone on the Integral Barrel -HDPE
250 140
Integral Rate Standard Rate Integral Amps Standard Amps
72
120
70
200
100 68
Am ps (Line G raph)
K g/Hr (Bar Graph)
66
150
80
64
60
°C
100 62
60
40
50 58
20
56
0 0 54
25 50 75 100 125
RPM 52
25 50 75 100 125
Figure 11-Effect of Rate on Amps-HDPE RPM
Figure 14-Temperature of Feed on Integral
Integral Feedblock Compared to The Standard Feedblock on HDPE at
125 RPM
Barrel-HDPE
20000
18000
16000
14000
Pressure (KPa)
12000
10000
8000
6000
Integral
4000 Standard
2000
0
0 57 71 92 108 128 144 164 181 199 221 240
Pressure Transducer Location from Face of Drive Shaft (cm)
Figure 12-Barrel Pressure of HDPE at
125RPM