Abstract: A flattening device for flattening a metal workpiece includes a frame; a first tightening assembly at a first end of the frame; a second tightening assembly at a second end of the frame; a series of work rollers interposed between the first tightening assembly and the second tightening assembly, wherein the work rollers include a first upper roller and a second upper roller, and a third, lower roller offset and interposed between the first and second upper rollers; wherein the upper and lower rollers accommodate bends in the workpiece of up to five yield stresses.