Billow Forming

Billow Forming - a method of thermoforming sheet plastic in which the heated sheet is clamped over a billow chamber. Air pressure in the chamber is increased causing the sheet to billow upward against a descending male mold.

Similar to vacuum snapback except the heated sheet is blown upward into a bubble shape and then the plug or mold is driven into the pre-stretched sheet from the top plate.

Using compressed air produces greater stretching forces but requires a much stronger pre-stretch box.