How to avoid plate blocking in flexographic printing with flexo water-based fluorescent ink?
Release Time : 2025-10-11
Flexo water-based fluorescent ink can easily cause plate blocking in flexographic printing due to a mismatch between ink properties and process parameters. This can manifest as ink accumulation on top of dots, leading to bridging of dots in highlight areas or sticking of dots in midtones. Addressing this issue requires a comprehensive approach encompassing ink formulation optimization, plate parameter adjustment, equipment precision control, and process parameter matching.
The key to achieving a balance between surface tension and viscosity in the ink formulation is the surface tension. The surface tension of Flexo water-based fluorescent ink must be lower than that of the non-image areas of the plate. Excessively high surface tension can cause ink adsorption in non-image areas, leading to ink accumulation between dots. Adjusting the ink surface tension to a reasonable difference with the plate surface tension by adding surfactants can significantly reduce the risk of plate blocking. Furthermore, the viscosity of Flexo water-based fluorescent ink must be matched to the printing speed. Excessively high viscosity can result in poor ink transfer, while too low viscosity can easily cause ink flying. This requires dynamic adjustment based on actual production conditions.
The matching of the line count in the plate parameters with the line count of the anilox roller directly impacts the ink application rate. The ratio of the line count of the printing plate to the line count of the anilox roller must adhere to a quantitative principle. That is, the minimum dot diameter of the printing plate should be no smaller than the cell opening diameter of the anilox roller. Using a high-line count printing plate (e.g., 200 lines/inch) with a low-line count anilox roller (e.g., 600 lines/inch) can easily cause small dots to sink into the cells, causing plate jams. In actual production, test strips can be used to observe dot morphology. If an abnormal increase in the 1% dot area is observed, the line count of the anilox roller or the printing plate should be adjusted promptly.
The radial runout of each roller within the equipment's accuracy must be strictly controlled. The radial runout of the anilox roller, plate cylinder, and impression cylinder must be within specified limits. Exceeding these limits can lead to uneven printing pressure and localized plate jams. Regularly check and adjust the roller parallelism to ensure that the parallelism of each roller within the same color group meets the required tolerances to prevent abnormal ink transfer caused by mechanical vibration. Furthermore, excessively wide rotation angles in the web-correcting device can lead to uneven tension on both sides of the paper, causing wrinkles and plate jams. This requires adjusting the web-correcting roller to its automatic mode by slowing down the machine.
Coordinated control of printing pressure and drying temperature is crucial among process parameters. Excessive inking pressure can easily cause deformation of plate dots and ink spillage; excessive inking pressure can significantly enlarge dots and increase the risk of plate jams in highlight areas. In actual production, pressure should be adjusted dynamically based on the characteristics of the printed product. For example, pressure should be increased appropriately when printing fine text and reduced when printing large solid areas. Regarding drying temperature, excessively high temperatures can cause filming on the ink surface, preventing the solvent from evaporating and resulting in a "false dry" phenomenon. Air volume and temperature should be adjusted according to the ink drying speed to ensure thorough drying.
Plate surface treatment can significantly improve plate jams. Spraying a low-surface-tension silicone neutral release agent on the plate surface can reduce surface tension in the plate's recessed areas, minimizing ink absorption. After spraying, the plate should be blown dry with compressed air to prevent solvent evaporation and a rise in surface tension. Furthermore, when making your own printing plates, adjusting the drying time, post-exposure, and post-processing time can optimize plate hardness and surface tension, extending the printing cycle.
Maintaining the Flexo water-based fluorescent ink circulation system can help prevent plate blockage. Regularly inspect the ink circulation lines to prevent air ingress and foaming. Use a steel mesh to filter the ink to remove impurities and paper dust, which can reduce anilox roller cell clogging. For equipment that has been idle for extended periods, thoroughly clean the ink circulation system to prevent ink solidification.