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- PVC Pipe Extrusion Start-up Procedure
PVC Pipe Extrusion Start-up Procedure
- By Skip Thacker
- Published 04/8/2007
- Extrusion
- Unrated
Skip Thacker
BIOGRAPHIC BACKGROUND
EDUCATION:B. A. in Chemistry,Wabash College, 1956
MBA Program, Xavier University, 1960-61
TECHNICAL
ORGANIZATIONS: Society of Plastic Engineers, Fellow Emeritus Grade Member; Vinyl Division,
The Chlorophiles.
PROFESSIONAL
EXPERIENCES:Over 35 years in research,
development, technical services, sales and marketing activities centered primarily on polymer additives to improve processing and end-use properties of plastics. Currently retired, but available for PVC help.
pg 1
Rigid PVC Pipe: Start-Up
Although this procedure describes CM-80 twin screw pipe extrusion start-up using pressure sizing, many of the same steps are also necessary for any extrusion process, regardless of end product or extruder type.
A. Assuming die is on machine properly, double check all electrical hookups,
match each heat zone with proper controls on panel.
B. Heat controls should be set at 300 F, 150 C across the board. Arrange to
have heats turned on a couple of hours prior to start-up, so as to give the
head and die a good "heat soak" period. This a good time to check heater
bands and controllers to make sure all work properly.
C. Turn up heats to roughly the following profile:
BARREL ZONES
____1____ ____2____ ____3_____ ____4_____
350-360 F 340-350 F 320-340 F 300-320 F
175-180 C 170-175 C 160-170 C 150-160 C
ADAPTER SPIDER- DIE VARIAC for MANDREL(pin) SCREW OIL
350-360 F 370-380 F 20-40% 300-320 F
175-180 C 185-195 C
150-160 C
Give the die at least an hour or two to arrive at final temperatures before
putting powder in machine. And give the die bolts a final tightening down!
Meanwhile, make sure powder blend is ready, and vacuum or pneumatic
system to the hopper is in operating order.
D. Put powder inhopper and follow this sequence:
1. Turn on extruder - slow speed (500-750 drive RPM).
2. Turn on feeder screw - slow speed (1.5 set) and feed just a little powder into screw flights (1/3 to1/2 full).
3. Watching at vent (no vacuum yet), and watching amps and back pressure, let material start coming out of die. (This may take 10-15 minutes at slow speed).
4. Gradually increase extruder speed to 1000, then 1500 RPM - watching amps. And after each increase in screw speed, increase feed rate to keep screws partially (1/3-1/2 ) filled.
5. After the purge compound is all pushed out, the initial pipe material will look cold out of die - but this should improve as RPM and feed are gradually raised. Look for a stock temperature (needle pyrometer) of about 370-380 F (185-195 C). Once at a reasonable production (1700 RPM to 2000 RPM) speed, gradually increase feed rate so screws are full - again watching amps. AMP readings in the 35-60 range are probably okay - start to worry above 60 amps. Remember to always increase screw RPM before increasing feed!
E. Once this speed is obtained with full screws, look at material in vent. It
should be a slightly damp to "cheesy" powder so that a vacuum can be
pulled without pulling a lot of powder (a little "snow" is okay). If not fused
enough, increase zones 1 and 2 by 10-20 F each. If too fused, decrease
zones 1 and 2 by 10-20 F each (5-10 C)
Although this procedure describes CM-80 twin screw pipe extrusion start-up using pressure sizing, many of the same steps are also necessary for any extrusion process, regardless of end product or extruder type.
A. Assuming die is on machine properly, double check all electrical hookups,
match each heat zone with proper controls on panel.
B. Heat controls should be set at 300 F, 150 C across the board. Arrange to
have heats turned on a couple of hours prior to start-up, so as to give the
head and die a good "heat soak" period. This a good time to check heater
bands and controllers to make sure all work properly.
C. Turn up heats to roughly the following profile:
BARREL ZONES
____1____ ____2____ ____3_____ ____4_____
350-360 F 340-350 F 320-340 F 300-320 F
175-180 C 170-175 C 160-170 C 150-160 C
ADAPTER SPIDER- DIE VARIAC for MANDREL(pin) SCREW OIL
350-360 F 370-380 F 20-40% 300-320 F
175-180 C 185-195 C
Give the die at least an hour or two to arrive at final temperatures before
putting powder in machine. And give the die bolts a final tightening down!
Meanwhile, make sure powder blend is ready, and vacuum or pneumatic
system to the hopper is in operating order.
D. Put powder inhopper and follow this sequence:
1. Turn on extruder - slow speed (500-750 drive RPM).
2. Turn on feeder screw - slow speed (1.5 set) and feed just a little powder into screw flights (1/3 to1/2 full).
3. Watching at vent (no vacuum yet), and watching amps and back pressure, let material start coming out of die. (This may take 10-15 minutes at slow speed).
4. Gradually increase extruder speed to 1000, then 1500 RPM - watching amps. And after each increase in screw speed, increase feed rate to keep screws partially (1/3-1/2 ) filled.
5. After the purge compound is all pushed out, the initial pipe material will look cold out of die - but this should improve as RPM and feed are gradually raised. Look for a stock temperature (needle pyrometer) of about 370-380 F (185-195 C). Once at a reasonable production (1700 RPM to 2000 RPM) speed, gradually increase feed rate so screws are full - again watching amps. AMP readings in the 35-60 range are probably okay - start to worry above 60 amps. Remember to always increase screw RPM before increasing feed!
E. Once this speed is obtained with full screws, look at material in vent. It
should be a slightly damp to "cheesy" powder so that a vacuum can be
pulled without pulling a lot of powder (a little "snow" is okay). If not fused
enough, increase zones 1 and 2 by 10-20 F each. If too fused, decrease
zones 1 and 2 by 10-20 F each (5-10 C)
