EXTRUDER DIES

 

EXTRUDER DIES

Extruder

Sheet and Cast Film

• The convention between cast film and sheet is that film is less than 0.01 inch thick and sheet is more than 0.01 inch thick.
• The key components in a sheet/film extrusion line are: die, three-roll stack or cooling rolls, puller or nip rolls, and windup or sheet stacking system.
• The sheet die should uniformly distribute the polymer melt across the  entire die width. This is to provide a uniform melt thickness and polymer flow to the three-roll stack. Die width typically range from approximately 24-120 inches (0.6-3 meters.
• Cast film/sheet is produced using a multiple roll stack. Depending on the thickness, film is wound in continuous rolls and sheet is cut to length and stacked.

• The die is designed to fit between the rolls in a three-roll stack and lay the sheet down on the roll.
• Roll diameters generally range between 8 and 16 inches.
• Roll stack designs are simple 'up' or 'down' stacks to control the entry and exit angle and the total wrap.
• Higher wrap provides more cooling as the rolls have more contact time to remove heat.
• The rolls control the cooling rate, final thickness , and surface finish.

Die designs

• Three common die designs are coat hanger die, T-die, and fishtail die.

• Thickness control

• Pipe extrusion line

• Pipe line

• Profile die

• Wire coating die

• Blown film die

Breaker Plate

• Breaker Plate: A metal plate installed in the flow channel between the end of the extruder screw and the die adapter with holes or slots to allow polymer flow.
• It commonly holds screens for filteration and changes the motion of the melt before it reaches the die.

Die swell