This video shows a full CNC plate roll equipped with 4 rolls capable of bending up to 18-14 gauge stainless steel. 

To watch it bend an oval muffler click here: http://cmlmachinery.com/watchvideo/cml-plate-roll-oval-muffler/

Or for a triangle muffler click here: http://cmlmachinery.com/watchvideo/cml-plate-roll-triangle-muffler/