Manufacturing corrugated tubing - GIF

[albertq]

I think it's pressurized air... you can see the 2 large holes in the middle of that large nozzle that extruding the plastic at the start. They seal off the end and then start going.
Altho, I also see the tubing on the outside, so there's a chance it also uses vacuum on the outside at the same time. Perhaps it's both.

I noticed those two large holes and initially thought compressed air, but the end of the tube is shown not sealed thus allowing the air to escape.