Abstract: A machine for forming parallel corrugations in a metal sheet and for welding each of these corrugations at its longitudinal end, comprises, on the metal sheet side, a bending die comprising two plates perpendicular to the metal sheet defining therebetween a space in which may be engaged a punch or knife perpendicular to the metal sheet. The bending die has, at each of its two lateral ends and on the internal faces opposite its parallel plates, a pair of bending members projecting from the internal faces of the two parallel plates of the die. These two bending members define therebetween a gap substantially equal to twice the thickness of the metal sheet. A welding torch is carried by the bending die and ensures welding of the two lips of the metal sheet in the immediate vicinity of the zone where they are nipped between the bending members.