System for friction stir welding including a mobile counter-bearing

A friction stir welding system for welding at least two parts to be assembled, the friction stir welding system comprising:

• a welding unit which includes a welding device which includes at least one welding head provided with a rotating pin;
• a counter-bearing unit which offers a support surface designed to support the parts to be assembled against a pressure exerted by each of the at least one welding head;
• wherein:
• the at least one welding head is moved relative to the support surface of the counter-bearing unit, in a first direction parallel to an axis of rotation of the rotating pin of each of the at least one welding head;
• each of the at least one welding head is moved in a second direction which is orthogonal to the axis of rotation of the rotating pin of the at least one welding head;
• the counter-bearing unit is configured for moving the support surface along the second direction;
• wherein the counter-bearing unit includes two clamp rollers set apart from each other and which have a common axis of revolution which is substantially orthogonal to the first direction and orthogonal to the second direction, where each of the clamp rollers has a main circumferential track which forms at least one part of the support surface;
• and
• wherein the counter-bearing unit is configured for moving the clamp rollers towards each other so that two respective side-walls of each of the clamp rollers are configured to contact and sandwich a portion of a first part of the at least two parts between the two respective side-walls, and the side-wall of each clamp roller is connected to the corresponding main circumferential track by a curved circumferential part.