A dual edge binder machine and operating method. The dual edge binder machine includes a heat device configured to deliver heat adjacent to an interface between an upper roller and a lower roller. The dual edge binder machine further includes at least one motor rotationally coupled to the upper roller and the lower roller, respectively.

A welding device (70) includes a probe assembly (90) including at least a first and second probe device (100a, 100b). A first and second part (31a, 31b) to be joined along the weld line (40) are provided, wherein the parts are each formed as a laminate (1; 1) including at least a first layer (2a, 2b) formed with a first material and a second layer (5a, 5b) formed with a second material. The first and second materials have different material properties. The method friction stir welds of the parts using the welding device, wherein simultaneously the first probe device acts on the first layers and the second probe device acts on the second layers.