Bubble Wrap - How do they do it

Bubble Wrap manufacturing starts as polyethylene resin, in the form of beads about the size of pea gravel. The beads go into an extruder - a long cylinder with a screw inside that runs its entire length. As the screw is turned, heat builds up and the resin melts into a liquid that is squeezed out of the cylinder into two stacked sheets of clear plastic film. One layer of the film is wrapped around a drum with holes punched in it, and suction is applied drawing one web of film into the holes that form the bubbles. The second layer of film is then laminated over the first so that when the two films are joined, they stick together and trap the air in the bubbles