The hottest flexographic printing solution

Flexographic printing solution

case 1: the influence of typesetting direction on the quality of flexographic printing products

the resin version of flexographic printing is easy to deform due to its certain elasticity (hardness at shore °), so controlling many enterprises has made clear that the power battery is the future development direction, and the pressure in printing and typesetting direction are of great significance to better obtain the point reproduction of the original

phenomenon: a pattern composed of words and thick lines, when typesetting, because only the processing of the subsequent process is considered, the pattern is arranged 90 ° perpendicular to the paper direction, that is, there are wide and long bars and fields in the horizontal direction of the printing roller. It is found that no matter how the printing pressure is adjusted, the pattern lines and edges on the print are always subject to pressure imprinting deformation, In addition, during printing, the printing plate roller jumps violently (the force on the non patterned part is uneven)

analysis: because the pattern is arranged horizontally, there is always a repeated mutation process of pressure from 0 state to 100% field, and then from 0 state to 100% field during the printing process. Therefore, there is the phenomenon of pattern edge imprinting deformation, which also causes the violent beating of the plate roller

solution: Based on the above analysis, the layout direction has been changed again, that is, the pattern is arranged circumferentially along the paper direction, so that the printing plate roller, ceramic grain roller and embossing roller work evenly from beginning to end. When printing on the machine again, the beating of the printing plate roller is normal, and the printing quality is greatly improved

therefore, colleagues should be reminded that in the prepress design process, the ideal pattern should be continuous patterns such as slashes and curves, which should be typeset along the direction of paper

case 2: how to deal with the problem of printing on the spot in a large area

in the production of flexographic printing, due to problems such as paper, roller, ink, printing pressure and so on, we often encounter large-scale on-the-spot false, blooming and other phenomena. In packaging and printing, this kind of problem is particularly serious when using paper with low surface smoothness and easy to lose powder

phenomenon: a flexographic printing machine in the author's company always feels that the ink layer is not thick enough in daily production, especially when printing a large area of the field. By adjusting the ink viscosity and increasing the printing pressure, this phenomenon is alleviated at a low speed of 30-50 M/min. however, when the speed gradually increases to more than 80 m/min, this phenomenon reappears, and the faster the speed is, the more obvious the phenomenon of false and blooming

analysis: due to the limitation of the corrugated roller configuration and the inability to carry out secondary printing, the problem can only be solved from other aspects. We observed that the roller scraper on the printing machine is a reverse scraper. Due to the shear force of the ink and the printing pressure cannot be too large, the ink is actually reduced. At present, following this idea, we should consider increasing the amount of ink

solution: adjust the direction of the scraper to install it in the positive direction. The phenomenon of large-area virtual printing has been improved when starting up the trial printing, and the effect is more obvious at high speed. Since then, in production, we choose the forward or reverse scraper installation according to the nature of printing, printing plate and so on, and such problems rarely occur. However, this method should be applied flexibly according to the requirements of printing quality and the actual situation

case 3: how to deal with paper wrinkling in tissue printing

in flexographic printing, the traction roller is one of the most important parts. Among them, the tension balance of the traction rubber roller is very critical. If it is not adjusted and maintained properly, or it is worn after long-term use, it may cause inaccurate overprinting and increase of waste products

phenomenon: when a 650mm flexographic printing machine of the author company was printing 40g single offset paper, it was found that there were often irregular folds on the edges of the printed matter. At first, it was suspected that the tightness of both sides of the base paper was inconsistent. Later, when the paper was changed, there were still folds

solution: after observation, we found that the paper wrinkled significantly when it came out of the printing traction part, so we stopped the machine to check the traction roller, and found that the roller surfaces at both ends of the traction rubber roller were seriously worn due to the accumulation of ink on the embossing roller, so we removed the roller to put the diameter back on the cylindrical grinder for processing and rounding, and started the machine for trial printing. The situation was improved, but the paper wrinkle was still not completely eliminated. Therefore, we traced the inspection scope back to the secondary tension mechanism and checked the tension system. It was found that the tightness of both sides of the paper coming out of the secondary tension roller was different. There were wrinkles formed by longitudinal stretching on the paper surface, which became obvious wrinkles after passing through the traction roller

after analysis, we believe that this is because the tension on both sides of the secondary tension roller is inconsistent (1) the universal material testing machine is not obviously exposed, but the paper is wrinkled due to the re extrusion of the traction roller when entering the printing area. Readjust the bolts on both sides of the secondary tension roller to make it balanced. When starting the printing again, the paper wrinkling phenomenon is completely eliminated

Case 4: Tips for repairing the embossing roller

in the flexographic press, the accuracy of the embossing roller in the printing department is the key component of the whole flexographic press, and plays a decisive role in the quality of printing. Therefore, 80% to 90% of all kinds of mechanical parts damage to the imprint roller is caused by fatigue fracture, which is of special significance in the whole printing production

phenomenon: the author company once had such a thing. Due to the negligence of the operator, during the operation of the machine, a screw slipped due to the vibration of the machine and fell directly into the gap between the embossing roll and the traction roll. It was too late for the emergency shutdown, and a slender dent was marked on the embossing roll. During printing, there is an obvious streak on the paper, which is different from the printing surface. The printing surface is unqualified, and the whole machine cannot run

solution: the embossing roller belongs to the benchmark part of the equipment, and it is difficult to disassemble, so the printing factory is inconvenient to return to processing, so we can only think of other ways to make up for it. Our method is to use high-quality paint and atomic ash to prime the indentation of the imprinting roller. After it dries, it becomes a coating with high hardness and no fear of water, and then use 800 mesh water sandpaper to polish it smooth. Even if the imprinting roller returns to the original appearance state (high-precision cylindrical), and then start the machine for trial printing, the impression on the original print disappears. Although people don't want to see this kind of failure, this method is a good remedy in an emergency

reprinted from: Chinese labels and stickers