Improved Ink Registration through Advanced Steel Belt Steering

摘要

Manufacturing equipment for single-pass digital printing faces an interesting challenge to deal with the growing productivity demand in combination with rising droplet registration accuracy. Although the administration speed of print-heads is still rising, high throughput speeds and/or increased print resolution can only be achieved by using multiple heads in series. Given at least 4 different inks, the distance between the first and last print-head can become more that a meter. When the relative registration accuracy over such a distance must be less than 10 micrometer, an intense fusion of multiple engineering disciplines becomes essential. In order to eliminate the mechanical (e.g. elasticity) properties of the substrate, a steel belt conveyer using vacuum technology for substrate clamping is introduced. Many conventional steel belt conveyors and their steering systems can't meet the previously mentioned accuracy target. By introducing actuated Axially Movable Segments Rolls (AMSR), the 2 surface orientations (X, Rz) of the belt (and therefore the substrate) can be continuously controlled, without deformation of the belt. On both sides of the rolls there are reluctance force actuators for segment manipulation. During rotation, the belt (always) will translate axially with respect to the segments that are in contact due to given limitations in belt and/or roll manufacturing (e.g. accuracy of the weld perpendicularity). The actuated AMSRs compensate this translation, based on the measured belt position. Once per revolution, when the segment is not in contact with the steel-belt, it will be actively positioned back to its 'center' position to minimize disturbances in the system. A demonstrator has been build to validate the actuated AMSR technology.