Production line of slats for roller shutters, comprising: - a profiling machine suitable to form a closed hollow, box section profile from a metal strip, making it slide along a longitudinal direction of advancement; and - a foaming machine, integrated in the profiling machine and suitable to dose inside the hollow, box section profile, partially open while it is being formed, a predetermined quantity of a mixture of polyol and isocyanate in a unit of time by means of an injection nozzle which can be positioned in a predefined dosing position along said longitudinal direction of advancement, characterized in that it comprises an optical acquisition device which is arranged in proximity to said predefined dosing position and is suitable to capture, preferably continuously, images of the jet of polyol and isocyanate mixture dispensed by said injection nozzle, and in that it comprises a control system which is connected to said optical acquisition device to capture the images of the jet generated by said device and is configured to compare the captured images with at least one reference image of the jet stored in memory means associated with said control system so as to verify whether the captured images of the jet are comparable within predefined error margins with said reference image or whether they deviate from it, wherein said reference image is relative to a jet related to a correct foaming of the hollow, box section profile, partially open while it is being formed, said control system being programmed to activate an alarm procedure in the event in which a deviation from said reference image is detected. - a profiling machine suitable to form a closed hollow, box section profile from a metal strip, making it slide along a longitudinal direction of advancement; and - a foaming machine, integrated in the profiling machine and suitable to dose inside the hollow, box section profile, partially open while it is being formed, a predetermined quantity of a mixture of polyol and isocyanate in a unit of time by means of an injection nozzle which can be positioned in a predefined dosing position along said longitudinal direction of advancement, characterized in that it comprises an optical acquisition device which is arranged in proximity to said predefined dosing position and is suitable to capture, preferably continuously, images of the jet of polyol and isocyanate mixture dispensed by said injection nozzle, and in that it comprises a control system which is connected to said optical acquisition device to capture the images of the jet generated by said device and is configured to compare the captured images with at least one reference image of the jet stored in memory means associated with said control system so as to verify whether the captured images of the jet are comparable within predefined error margins with said reference image or whether they deviate from it, wherein said reference image is relative to a jet related to a correct foaming of the hollow, box section profile, partially open while it is being formed, said control system being programmed to activate an alarm procedure in the event in which a deviation from said reference image is detected. characterized in that it comprises an optical acquisition device which is arranged in proximity to said predefined dosing position and is suitable to capture, preferably continuously, images of the jet of polyol and isocyanate mixture dispensed by said injection nozzle, and in that it comprises a control system which is connected to said optical acquisition device to capture the images of the jet generated by said device and is configured to compare the captured images with at least one reference image of the jet stored in memory means associated with said control system so as to verify whether the captured images of the jet are comparable within predefined error margins with said reference image or whether they deviate from it, wherein said reference image is relative to a jet related to a correct foaming of the hollow, box section profile, partially open while it is being formed, said control system being programmed to activate an alarm procedure in the event in which a deviation from said reference image is detected.