High-tech and Operational Points in Flexo Printing (Chinese)

High-quality ceramic anilox rolls require a strong resistance to abrasion and breakage (ie, the hardness and toughness of ceramics), but ordinary ceramics are not ideal in both cases. Today, a high-tech ceramic, nano-ceramic, is also beginning to be applied to anilox rollers. The characteristics of nano-ceramics are mainly in the mechanical properties, including the hardness of nano-ceramic materials, fracture toughness and low temperature ductility. Due to the nano-ceramics in the microstructure, the grain size, grain boundary width, second phase distribution, and defect size are all on the nanometer level. Thus, the strength, toughness, and superplasticity of the material are greatly improved, which greatly overcomes many shortcomings such as large brittleness (cracks), poor uniformity, low reliability, poor toughness, and poor strength of the engineering ceramic, so that the ceramic has a metal-like strength. , flexibility and ease of processing. For example, polycrystalline ceramics consist of grains of a few nanometers in size, which can become ductile at low temperatures and can undergo 100% plastic deformation. The nano-titania ceramic material has excellent toughness at room temperature, undergoes bending at 180° C. without cracks, and opens up new fields for replacing conventional ceramic applications. In addition, the mechanical properties of nano-scale ceramic composites, especially at high temperatures, make the hardness and strength higher. Compared with ordinary ceramic materials, nano-composite ceramics have greatly improved mechanical properties, surface finish, wear resistance, and high temperature performance. Studies have shown that the introduction of nano-dispersed phases in the micron-sized matrix for compounding can increase the fracture strength and fracture toughness of the material by 2 to 4 times. It can also increase the hardness and elastic modulus of the material and improve the creep resistance and fatigue resistance. Destructive performance. From the perspective of flexo development, people's demand for high-quality flexographic printing will continue to increase, but high-quality flexo printing requires an anilox roller with a high number of lines, and laser engraving of an anilox roller with a high number of lines, Roller ceramic hardness, toughness, etc. must have very good characteristics, in order to make the laser engraving of the cell contour clear, smooth wall, to ensure accurate ink transfer, so that the ink release performance is good, so as to print a good product. However, due to the brittleness of the texture of the general ceramic materials, the poor toughness and strength, together with the pre-processing technology and other issues, the processing accuracy of the ceramic anilox roll does not meet the requirements, and thus its application has been greatly limited. The application of nano-ceramics, due to the characteristics of nano-, nano-ceramics will overcome some of the defects of traditional ceramics, so that the ceramic hardness, toughness, wear resistance and other characteristics have greatly improved, which laid a good foundation for engraved anilox roller lay the foundation. Therefore, it was predicted that with the wide application of nanotechnology in ceramic manufacturing, ceramic anilox rollers may eventually eliminate all metal anilox rollers. Many experts believe that if it can solve the technical problem of inhibiting grain growth in the sintering process of single-phase nanoceramics, and thus control ceramic nanocrystals with a ceramic grain size below 50 nanometers, it will have high hardness, high toughness, and low temperature. The unparalleled advantages of traditional ceramics such as superplasticity and easy processing. Cahn, a well-known British material expert, pointed out that nano-ceramics are a strategic way to solve ceramic brittleness. For the flexographic printing anilox roller, when the anilox roller is processed by the plasma thermal spraying process, a high-quality ceramic coating is required to be sprayed on the surface of the substrate, and the coating hardness range is HV 300 to 1300, and the general porosity is required. The rate must be less than 1%. For anilox rollers above 1200 lines, the porosity must be less than 0.5%, and the coating structure must be uniform, without cracks, high hardness, and high density, so as to ensure that the texture The roller has very good precision in engraving high number of lines, improves the abrasion resistance of the anilox roller and resistance to acid, alkali and corrosion, etc., and improves the service life of the product and the quality of flexographic prints.

In the manufacture of anilox rollers, apart from nanotechnology and laser high-tech, a graphite carbon fiber material has been newly developed in the aerospace industry in recent years. Due to its light weight and hard characteristics, it is welcomed in the manufacturing industry. Invented in 1994, the carbon fiber core was quickly applied to the flexo-printed anilox roller core, which became a new generation of highly advantageous anilox rollers. Although steel rolls have long been the most preferred material for anilox rolls due to their physical properties such as strength, mechanical processing properties and durability, they are replaced by such carbon fiber roll cores instead of the conventional steel roll cores. Its strength is 2 times that of steel rollers and its weight is 1/10 that of steel rollers. The anilox roller of this carbon fiber core has been found out through trial and has the following advantages: (1) Since the carbon fiber anilox roller is particularly light, it is easy to handle in the roll change and labor is reduced. (2) Carbon fiber anilox rolls are not easily damaged during roll change, which saves a large amount of money for re-engraving new rolls. (3) In the driving part of the printer, the total weight of the carbon fiber anilox roller is 1/10 of the weight of the steel roller, which is beneficial to reduce the friction between the rollers and the service life of the anilox roller is accordingly increased, thereby reducing downtime. Time, increased productivity. When the speed of the printing press reached 3000 sheets per hour, the difference between the steel roll and the carbon fiber anilox roll was even more obvious. The steel core anilox roll beats a lot and in its center part, it is not able to maintain the solid image while the carbon fiber The anilox roller, however, can maintain a solid image across the roller surface. Although the carbon fiber anilox roller is light and hard, its offset is less than 1/10 of the steel core roller. The greatest benefit of this feature has greatly improved the printing quality of large flexographic printing presses.

Third, high-tech in the anilox roller cleaning

The anilox roller is a very precise mechanical part. Many uniformly shaped cells on the surface are evenly distributed. It plays a role of ink storage, ink distribution and quantitative ink transfer in printing. Since the cells on the anilox roller are very fine and delicate, the amount of ink filled in the ink cavity can be transferred to the plate only about 70% to 80%, and the remaining ink remains in the cell site. In the process of ink transfer, due to the dryness of the remaining ink, impurities in the ink, and other reasons, it will block the network and make the ink transfer poor. This not only affects the printing quality, but also increases the number of anilox rollers that are blocked by the mesh for a long time. The loss of large ink shortens the life of the anilox roll. Therefore, the anilox roller should pay great attention to maintenance and cleaning during use. In the anilox roller cleaning, there are currently four commonly used methods: chemical cleaning methods (such as chemical solvent brushing method, chemical solution immersion method); physical cleaning methods (such as medium blowing cleaning method; low pressure spray cleaning method; dry ice cleaning method; Plastic beads spray cleaning method); ultrasonic cleaning method; laser cleaning method. Laser cleaning is a high-tech method introduced in recent years. Laser cleaning technology refers to the use of a special lens to irradiate a high-energy laser beam on the surface of the anilox roller. Without damaging the wall of the anilox roller, the ink, adhesive, wax, silicone, and steel shavings remaining on the surface and the cell site remain. The residue vaporizes or evaporates instantly to form a solid powder to achieve cleansing. The laser cleaning method can clean 1200/inch or more anilox rollers without damaging the cell walls. It can completely remove the dry ink, adhesives, plates and scraper steel shavings. Compared with the traditional cleaning process, laser cleaning technology has the following characteristics: