1 Troubleshooting for Sheet Extrusion - LG MMA

oubleshooting for Sheet Extrusion (1)
Types of Defects
Causes
Countermeasures
Insufficient mixing of molten resin
Moisture content
Use proper screw.
Increase the pressure.
Lower the temperature and the screw speed.
Pre-dry or use extruders with ventilation equipment.
Specks or marks Roll is too cold. Increase roll temperature.
Contamination
Locked air
Dirty rolls
Use finer screen.
Clean dies and handle raw materials with care.
Use other screws.
Use extruders with ventilation equipment.
Increase pressure and lower temperature of back cylinder and screw speed.
Wipe well with soft cloth.
Foldings
Inconsistent thickness
Rough surface
Increase temperature of mid roll.
Adjust temperature and tension of bottom roll.
Place external heater at the edge.
Check whether extrusion output is consistent.
Check whether correction bolt is broken.
Check the uniformity of raw materials.
Inspect changes in temperature and pressure.
Use heavy dies.
Increase the temperature of molten resin inside the die.
Use a subsidiary polisher.

oubleshooting for Sheet Extrusion (2)
Types of Defects
Causes
Countermeasures
Die Lines
Clean die lips.
Streaks in the direction Moisture content Pre-dry or use extruders with ventilation equipment.
of extrusion Sooted rolls Re-polish the roll surface.
Streaks perpendicular to
Lamination roll is too cold.
Caking on rolls.
Increase the temperature of lamination roll.
Lower the roll temperature, the temperature of molten resin,
or the temperature of blow air between sheet and roll.
extraction Poor take-off unit or die. Fix take-off unit and improve die prop.
Curvatures on the surface
Insufficient mixing of molten resin
Use other screws.
Increase the extrusion pressure.
Lower the screw speed.
Decrease the temperature.
of extrusion products Big rolling bank between roll gears. Decrease the pressure between rolls.
Uniformalize thickness of sheets in the die.
Increase the speed of take-off.
Lamination is too hot.
(Small curvatures at the edges)
Lower the temperature of laminating roll.
Inspect the roll surface.
Clean inside the roll if possible.