1. The machine operator pours the polyethylene resin into the hopper.
2. The hopper feeds the resin into the extruder.
3. Heating elements and the turning of the extruder screw melts the
resin into molten form and forces it through the extruder.
4. The molten poly flows evenly up and over the circular die.
5. As the molten poly emerges from the die, the machine operator:
a. Grabs it wearing protective gloves.
b. Pinches the molten poly together.
c. Ties a rope to the top of the molten poly. The rope leads upward
to a pulley system.
d. Pulls the other end of the rope to move the molten poly upwards.
At the same time, the air ring blows cool air upwards, which
solidifies the molten poly.
6. As the tubular shape moves up, the machine operator inserts an air
gun through the poly film to blow in additional air. This step is
repeated until the diameter of the tubular poly film reaches the
required bag size.7. Along the length of the tower are guides to keep the tubular poly film
from shifting. As the film reaches the top of the cooling tower, the
guides gradually flatten it into a layflat form.
If the plastic bag will have gussets, special frames (called “gusset
boards”) indent the sides of the tube before it is flattened.
8. At the top of the cooling tower, motorized nip rollers grab the
solidified poly film. The nip rollers now take over the job of moving
the poly film up the cooling tower.