 |
|
Problem
|
|
Possible Cause
|
|
Possible Solution
|
|
|
Rough Surface
|
|
Melt too cold
|
|
Increase barrel temperature
|
|
|
|
|
|
|
Increase die temperature
|
|
|
|
|
Heaters not working
|
|
Check thermocouples and heater bands
|
|
|
|
|
Melt not mixed
|
|
Use higher compression ratio screw or screw with mixing section
|
|
|
|
|
Die design
|
|
Decrease land length
|
|
|
Uneven Cross Section
|
|
Surging
|
|
Decrease extrusion rate
|
|
|
|
|
|
|
Use screw with longer feed or metering section
|
|
|
|
|
|
|
Use screen pack to increase back pressure
|
|
|
|
|
|
|
Decrease die temperature
|
|
|
Black Specks / Undispersed Lumps
|
|
Contamination
|
|
Purge with low melt flow PP or HDPE
|
|
|
|
|
|
|
Check the colour concentrate is based on PS,PP or PE - not PVC
|
|
|
Odor / Yellowing
|
|
Melt too hot
|
|
Decrease die and barrel temperature
|
|
|
|
|
|
|
Decrease screw speed and back pressure
|
|
|
Voids
|
|
Moisture
|
|
Dry pellets
|
|
|
|
|
|
|
If using vacuum check that vent is unplugged
|
|
|
High Extruder pressure / Low Throughput
|
|
Melt too cold
|
|
Increase extruder temperature
|
|
|
|
|
|
|
Increase die temperature
|
|
|
|
|
Clogged screen pack
|
|
Clean/Replace
|
|
|
|
|
Heaters not working
|
|
Check thermocouples and heater bands
|
|
