A working process of a machine for wrapping products in packages, carried out with a thermoplastic material film from a reel, comprising: - a loading station for the products to be packaged; - a hollow mandrel with a relative forming shoulder; - a sealing device for forming a seal of the longitudinal edges of the film; - a horizontally mobile pusher for pushing a bundle of products from the loading station through the mandrel; - a sealing and transversal cutting assembly formed by two vertically mobile elements (108, 208) mounted on a horizontally mobile primary carriage - a conveyor - a secondary carriage carried by the primary carriage; comprising the following operating steps: - positioning the sealing device in a position for sealing the overlapped longitudinal edges of the film while forming a new tubular film casing; - arranging the elements (108, 208) of the assembly in a closed position on the head portion of the new tubular film casing and on the tail portion of the tubular film casing of a finished package; - and conveying of said new tubular film casing, by the movement of the primary carriage away from the mandrel, and repeating the preceding steps so that the product placed inside the tubular casing by the mandrel is wrapped in a tight adherent manner due to the elastic retraction of the film of tubular casing, characterised in that the transversal section of the mandrel is reduced to a diameter smaller than the diameter of the bundle of products in respect to the overall transversal dimensions of the bundle in a first operating step, and when the sealing and cutting assembly is in the stop end position away from the mandrel, the longitudinal sealing device is in the rest position, the elements (108, 208) of the assembly open, and the mandrel transversally widens, widening the length of the tubular film casing arranged outside of the mandrel itself and the bundle of products present in the loading station is slightly compressed to allow the bundle to enter inside the mandrel, and that in a further operating step prior to the intervention step of closing the elements (108, 208) that pinch the tubular film casing, the mandrel transversally reduces and the pusher starts the step of moving backwards so as to arrive upstream of the loading station so it can start a new packaging cycle. - a loading station for the products to be packaged; - a hollow mandrel with a relative forming shoulder; - a sealing device for forming a seal of the longitudinal edges of the film; - a horizontally mobile pusher for pushing a bundle of products from the loading station through the mandrel; - a sealing and transversal cutting assembly formed by two vertically mobile elements (108, 208) mounted on a horizontally mobile primary carriage - a conveyor - a secondary carriage carried by the primary carriage; - positioning the sealing device in a position for sealing the overlapped longitudinal edges of the film while forming a new tubular film casing; - arranging the elements (108, 208) of the assembly in a closed position on the head portion of the new tubular film casing and on the tail portion of the tubular film casing of a finished package; - and conveying of said new tubular film casing, by the movement of the primary carriage away from the mandrel, and repeating the preceding steps so that the product placed inside the tubular casing by the mandrel is wrapped in a tight adherent manner due to the elastic retraction of the film of tubular casing,