Advantages of flexo technology in packaging printing

        Many countries in the world have used flexo printing for newspaper printing, and in the United States alone, more than 40 printing plants have used flexo printing to print newspapers; while in Germany, flexo printing is mainly used for packaging printing, and flexo printing occupies a large market share in the packaging printing market. share has been steadily increasing. In recent years, the quality of flexo printing has been greatly improved. Shaftless printing machines, high-line anilox rollers, high-performance inks, and laser-engraved flexo plates have all contributed to improving the quality of flexo printing.

1. Direct Drive Flexo Printing Machine

        Shaftless transmission technology was initially only applied to some narrow-width small web flexo printing machines. In 1998, the first shaftless satellite-type flexo printing machine developed by W&H for the flexible packaging flexo printing market was put on the market. Information from manufacturers shows that almost all newly installed flexo printing machines in Europe use shaftless drive technology. However, due to economic reasons, some countries still use traditional shaft drive flexo printing machines.

        What are the advantages of shaftless transmission technology? Shaftless transmission technology enables all processing processes to be completed steplessly through the so-called "electronic wave", without the need for gears, without any vibration, and the length of repeated printing is easier to adjust. Print flexible materials with large variations in elongation. Since the shaftless flexo printing machine can individually adjust the overprint accuracy of each color group, the overprint accuracy of the printed product is higher, which not only improves the printing quality of flexible packaging flexo printing, but also is very good for direct flexo printing on corrugated cardboard. There are benefits. For example, on BOBST's flexo printing machine, only the printing color group is driven by the shaftless drive, and the other parts of the printing machine still use the traditional transmission method.

2. High quality anilox roller

        Another innovative technology in flexo printing is the anilox roller. Six years ago, the motto of the flexo printing industry was: "The thinner the anilox roll, the better". Now, people don't say that any more. Manufacturers are concentrating on developing anilox rollers with new mesh shapes, or improving the surface properties of anilox rollers by spraying ceramic materials on their surfaces. In the field of flexible packaging printing, flexo printing is competing with gravure printing for the market, and the anilox roller is a key element affecting the quality of flexo printing. Whether flexo printing can win the competition with gravure printing depends on the technological development of anilox rollers.

3. Optimized printing color

        The impact of the development of anilox rollers on printing colors cannot be ignored. The higher the number of lines of the anilox roller, the lower the ink loading capacity. To meet the requirements of stable and full color, it is necessary to increase the content of binders in the ink and increase the concentration of pigments to achieve the desired level under the condition of low ink transfer volume. required ink film thickness. Although Germany still has reservations about printing folding cartons with UV flexo inks, companies in other countries that print high-quality flexo products have proved that UV flexo has great development potential. In particular, UV curable inks are odorless, have no volatile gases, and the printed products are bright in color and have good gloss, which is more and more favored by people.

        The development of drying technology makes the curing of the ink film faster, which makes the printing effect of flexo gold ink and silver ink even surpass that of offset printing. In recent years, ink pigments have been made finer, allowing the use of anilox rolls with higher thread counts, allowing the flexo process to reproduce finer images as well.

4. Use photosensitive resin plate digital imaging or direct engraving

        Since Drupa1995 exhibited the digital imaging flexographic plate for the first time, and Drupa2000 exhibited the polymer flexographic plate of direct engraving, a fierce debate has been going on: Which technology is superior in quality and economy? ?Direct engraving plate-making technology uses laser to engrave graphics and text on the surface of flexible plates. This method has been used to engrave rubber plates for more than 30 years. The flexographic direct plate-making technology uses a photosensitive resin flexographic plate with a black mask (LAMS) on the surface, exposes it on a flexographic CTP plate-making machine, removes the LAMS layer of the graphic part of the printing plate, and then performs UV exposure, washing and drying.

        In recent years, the quality of photosensitive resin flexographic plates has been improved day by day, not only with higher resolution, but also with shorter imaging time. The flexographic CTP system mostly uses 8 beams of Nd:YAG lasers to expose the flexographic plate, but after exposure, the printing plate must be exposed to UV for imaging and rinsed. The new plate-making technology, such as the CyrelFAST system, uses a special technology to remove the excess on the plate with high heat energy, and it can be used immediately without flushing. However, the CyrelFAST system still has limitations in the size of the printing plate format, but it is expected that it will solve the plate-making problem of large-format flexo plates in a short time.

5. Advantages of direct engraving flexo

        Although low-resolution direct engraving rubber plates are common in the market, the direct plate-making system exhibited at Drupa 2000 that engraves directly on BASF's polymer plates still attracted people's attention. However, some people criticized that the diameter of the CO2 laser beam used in this system is too large to achieve high resolution, and it is not economical, but this problem has been completely solved now. Because BASF and STK Schablonentechnik recently announced that the GRS in Germany installed the first direct engraving system of this kind, which can make the diameter of the light spot very small by overlapping the laser spots.

        In addition, the manufacturer of the direct engraving system has also improved the system. The laser beam is changed from 1 beam to 3 beams. Since the laser energy can be changed, the evaporated material can also be removed to different depths, thereby making the dots clearer. This is because CO2 laser and Nd:YAG laser are used. CO2 laser first forms a rough relief effect (mainly the depth of relief), while Nd:YAG laser can form different dots due to its smaller spot diameter. However, because Nd:YAG laser cannot be absorbed by all materials, it is limited in use.

6. Thin sleeve technology

        Another technology that promotes the improvement of flexo printing quality is the introduction and application of thin sleeve flexo. The thin sleeve technology combines the advantages of a single photosensitive resin flexo plate and a circular sleeve plate that is not easily deformed. First, the photosensitive resin flexo plate is mounted on a thin sleeve, and then imaged and rinsed. After the imaging of the plate is completed, it is loaded on the circular plate cylinder, thus avoiding image deformation. The price of this system is relatively high, so the application is not yet widespread.

        The development of flexo printing technology is still going on, whether it is flexo printing machine or anilox roller, whether it is ink or plate material, as well as registration control and closed scraper device, the development of these technologies will promote the improvement of the overall level of flexo printing technology .