a plastic welding machine for producing connection seams with thermal plastic foil or thermal plastic film . the folding device includes a fix support plate and a folding plate which is provided with a u - shaped guide stop and can be pivoted back and forth between a feed position and a working position . folding device can be folded open for introducing the edge strip of the material to be welded and then folded up where the edge strip is folded over in the shape of a u . a flat u - shaped guide sleeve is provided which may be pivoted into the folding device to produce lap joints on the two layers of the material to be welded .