A substrate printing system, comprising a perforated conveyor belt adapted for transporting on the same a substrate to be printed, wherein the perforated conveyor belt comprises a set of perforations, a perforated grill which comprises a set of perforations and which is configured such that the perforated conveyor belt can be moved over the perforated grill, a suction chamber which comprises a suction element, the suction chamber being in communication with the perforated conveyor belt and with the perforated grill such that the suction flow created by the suction element is adapted for passing through perforations (10, 20) of the perforated conveyor belt and of the perforated grill to secure the substrate to the perforated conveyor belt, the perforations of the perforated grill have a different pattern in an area adapted for printing substrates than in an area not adapted for printing substrates along a movement direction of the perforated conveyor belt over the perforated grill, or the system comprises blocking means (7, 8) for blocking perforations of the perforated grill, wherein said different pattern of the perforations or the blocking means (7, 8) are configured to at least partially block the suction flow through perforations (10, 20) to a greater extent in the area adapted for printing substrates than in the area not adapted for printing substrates along said movement direction, characterised in that the perforated grill is removable in the area adapted for printing substrates with respect to the area not adapted for printing substrates, or in that the blocking means (7, 8) are removable with respect to the perforated conveyor belt and/or the perforated grill. a perforated conveyor belt adapted for transporting on the same a substrate to be printed, wherein the perforated conveyor belt comprises a set of perforations, a perforated grill which comprises a set of perforations and which is configured such that the perforated conveyor belt can be moved over the perforated grill, a suction chamber which comprises a suction element, the suction chamber being in communication with the perforated conveyor belt and with the perforated grill such that the suction flow created by the suction element is adapted for passing through perforations (10, 20) of the perforated conveyor belt and of the perforated grill to secure the substrate to the perforated conveyor belt, the perforations of the perforated grill have a different pattern in an area adapted for printing substrates than in an area not adapted for printing substrates along a movement direction of the perforated conveyor belt over the perforated grill, or the system comprises blocking means (7, 8) for blocking perforations of the perforated grill, wherein said different pattern of the perforations or the blocking means (7, 8) are configured to at least partially block the suction flow through perforations (10, 20) to a greater extent in the area adapted for printing substrates than in the area not adapted for printing substrates along said movement direction, characterised in that the perforated grill is removable in the area adapted for printing substrates with respect to the area not adapted for printing substrates, or in that the blocking means (7, 8) are removable with respect to the perforated conveyor belt and/or the perforated grill.