Elaborate design of ink transfer system for the ho

The elaborate design of flexographic ink transfer system

traditional printing is an industry that copies a large number of words and images on paper, plastic, metal and other base materials, ranging from hundreds to tens of thousands. Its quality requirements are that the ink color is uniform, the depth is consistent, the text lines are clear, and there is no flower or paste. Colorful images are colorful, rich in layers and strong in three-dimensional sense. The reproduction should be faithful to the original or conform to the natural color, so the traditional printing method has made careful consideration and careful design of the ink transmission system to meet the requirements of ink transmission

basic requirements for the ink transfer system: ① there is enough reasonable ink volume, ② the ink volume should be uniform, and ③ the ink can be supplied repeatedly and quantitatively. In this way, we can meet the requirements of a large number of reproductions. Otherwise, one piece is deep, one piece is light, the ink is deep and light, and the text and lines are thick and thin, which cannot meet the quality requirements

in the early flexographic printing, the ink transfer system did not use the wrinkle roller, so the ink color was very unstable, and only products with low requirements could be printed. The wrinkle roller was developed through continuous improvement in practice

the ink transfer system of flexographic printing began to use rubber rollers, felt rollers and metal light rollers. The rubber roller was made of natural rubber. Its mechanical accuracy was not high and the ink was difficult to control, so at that time, it could only print some rough and simple paper bags; The felt roller uses the feature that the felt can absorb and release ink, but the service life of the felt is not long. Soon after use, the connecting material in the ink will harden the felt, and the felt will lose the feature of absorbing and releasing ink, so it is not ideal. Although the processing accuracy of the metal light roller is relatively high, and the gap between the two rollers can be used to control the ink volume, due to the tension of the ink, the ink will accumulate together and produce streaks one by one, resulting in uneven ink transmission, so the printing quality is not high

later, someone used the method of high-speed steel shot blasting on the surface of the metal smooth roller to improve the hardness of the metal surface, so that the surface of the metal smooth roller produced roughening and pits. Although the nature of the metal smooth roller was changed, and the ink was not easy to accumulate, the shot blasting could not ensure that the depth was the same as that of each roller; It has also tried to sinter ceramics on the steel roller to make it naturally shaped and equipped with a special correction thermometer insertion device to form irregular pits, but it is also difficult to control

in the 1930s, due to the development of photography and electroplating corrosion technology, copper was plated on steel rollers, and then printed with carbon paper or photographic film to corrode the metal roller. This kind of corrugation roller can be controlled due to the line and reproduction processing. Although it has made a big step forward and laid the foundation for the development of the corrugation roller, it is still not ideal:

① there are joints, and the ink volume at the joints is uneven; ② the line is thick, about 100L/in or less, and the thin one is not easy to manufacture and corrosion. In the early 1980s, when manufacturing the laminated flexographic printing machine in China, due to the high cost of imported metal corrugation rollers, corrosive corrugation rollers were used

the development process of things is always improved and improved. The development of corrugated rollers has been improved according to the advanced processing technology in different periods. Following the corrosion of corrugated rollers, metal rollers that are plated with copper on steel rollers and then mechanically carved and electronically carved have been used, resulting in ideal seamless metal rollers. However, the speed of mechanical engraving is slow, and the international influence of China's plastic machine industry continues to increase. Electronic engraving is carried out on steel (Shanghai Institute of printing technology once successfully developed and put into production the metal embossed roll directly engraved on the steel roll). Later, it developed the metal embossed roll directly processed on steel with mechanical extrusion technology. At present, the metal embossed roll of electronic engraving and mechanical extrusion is still widely used in corrugated box printing slotting machines, Laminated flexo printing machine, as well as coating equipment

no matter using electronic engraving or mechanical extrusion, the number of lines of the metal roller is generally below 3o0l/in, which cannot meet the ink transfer capacity of high-speed printing products. Only 80L/100L/in products such as processing materials can be printed, which also limits the improvement and development of flexographic printing quality

in the mid-1980s, laser technology was applied to develop the ceramic roller engraved by laser. The ceramic roller can process a high number of lines, has a wear-resistant surface, and can use an ink scraper, so that the ink transfer volume of the ink transfer system is more accurate and stable. Therefore, the emergence of ceramic roller not only further improves the ink transfer system of flexographic printing, but also meets the requirements of printing fine products, Promote the development of flexographic printing

people often say that the corrugated roller is the heart of the flexographic printing machine. As a corrugated roller, the ink transfer system cannot be formed in the printing machine. In the early stage, the ink transfer system was composed of two rollers rolling against each other, plus an ink tray, one of which was in contact with the printing plate and transferred ink to the printing plate, so it was very simple to form the ink transfer system. Therefore, people also call the ink transfer system of flexographic printing as short ink path, and the ink transfer system of offset printing as long ink path. This structure has been extended to the metal roller, and it is still the same today. Therefore, each color deck of flexographic printing machine is usually composed of four rollers (ink bucket roller, metal stripe roller, plate roller and embossing roller), which is often called four roller type

due to the emergence of metal corrugation rollers, people will naturally be associated with gravure printing. Gold creep refers to that the corrugation rollers of materials under constant load are very similar to gravure rollers. They are all composed of pits, and the surface is also coated with a layer of hard chromium. The ink transfer method of gravure printing with a scraper is more accurate than that of two roller pair rolling. Therefore, the characteristics of accurate ink transfer of gravure printing are naturally transplanted to the metal textured roller, and the ceramic textured roller has a harder surface, which is more suitable for the use of an ink scraper. Therefore, there is no ink bucket roller in the ink transfer system of flexographic printing, There is only one metal roller or ceramic roller and doctor blade, and the doctor blade is improved from the positive direction to the reverse and two-way closed ink chamber. The ink is supplied by the circulating pump, so that each color deck of the flexographic press is reduced from four rollers to three rollers, so it is also called three roller type

so far, the ink transfer system of flexographic printing has developed from the kingdom of necessity to the kingdom of freedom, from simple, uncontrollable ink volume to advanced and reasonable, which is simpler than before, and the ink volume can be controlled. Now it has become an ideal ink transfer system, which can reasonably configure the corrugated rollers according to different printing substrates and printing pieces

source: Guangdong Printing