The panels made in continuous stage are cutted to lenght by "on the fly" cutting machine with band saw or disk saw. In the first case the machine is equipped of a turn-blade device that permit to cut the panel on the both crossing side. On the front of machine can be installed a rotating disk cutting device that obtain on the both side cut for the overlapping on the roof panels. In the second case the machine is equipped by one circular saw that cut totally the panels or cut for the overlapping of roof panels. For the overlapping cut of roof panels is used one series of special knives that cut the insulating core inside the corrugation of the lower sheet.