Technical essentials of multicolor flexographic pr

Corrugated board multicolor flexographic printing technology points

generally speaking, the flexographic printing corrugated box process is to print directly on the corrugated board, using water-based ink. Now corrugated box production process also uses web pre printing method. Corrugated boxes adopt flexographic printing technology, accounting for about 95% in the United States, 85% in Western Europe and more than 93% in Japan. It is also gradually accepted by corrugated box manufacturers in China. In recent years, it has developed rapidly. At present, it is estimated that more than 50% of enterprises adopt this technology, and now more enterprises adopt corrugated board multi-color flexographic printing slotting machines

at present 1. Characteristics of flexographic printing

corrugated board flexographic printing has the following advantages: flexographic printing can not only copy the field version, but also copy the line version; Corrugated paper printing has developed from monochrome and two-color to multi-color line version, changing the situation of monotonous ink color and simple graphics and text in the past, and meeting the requirements of sales packaging, which is an inevitable law of development. Now the line plate is printed on corrugated paper (box, box), and it can be printed to 100 lines/inch on e corrugated, and 40 lines/inch on a, B, C corrugated. Flexo can make both field version and line version, which meets the printing requirements of corrugated boxes

flexible printing plate can compress and deform. Corrugated paper has the worst thickness error and surface flatness in the printing base material. Especially for a and C corrugated, the thickness error should be 0.5mm or even higher. Because the flexible printing plate is made of synthetic rubber as the main body, it can compensate for the thickness error and surface unevenness of corrugated paper with its own compression elastic deformation in the printing process, so as to meet the stamping requirements of each corrugated paper, make the ink color more uniform, and ensure the printing quality and reduce waste products. Flexographic plates can compress and deform, which is absolutely impossible for flat printing and gravure printing. Therefore, the thickness of flexographic plates used on corrugated boxes is relatively thick, generally 4 ~ 7mm, while the thickness of flexographic plates used for flexible packaging printing is only 1.14mm and 1.7mm. Why thick printing plates should be used on corrugated paper is to use its compression deformation. Now in order to reduce the cost, 4mm printing plates and 3mm air cushion rubber lining (plastic lining is not allowed), the effect is better. Of course, the force isokinetic control accuracy: better than the set value ± 1%, we should promote to strive for the basic consistency of the thickness and quality of corrugated paper. Thin printing plates are also used in corrugated paper printing (fine corrugated) abroad. The key is to control the surface flatness of corrugated paper

flexographic printing belongs to light pressure printing. Due to the corrugated paper, there is also a printing base material with uneven pressure. The pressure at the high part of the corrugated paper is large, and the pressure at the low part of the corrugated paper is light. It will also cause that the low part of the corrugated paper cannot contact the printing plate, and the ink cannot be printed. Therefore, both flat printing and gravure printing cannot overcome the defects of corrugated paper thickness error and uneven pressure. Flexographic printing belongs to light pressure printing, which is the lightest printing pressure in traditional printing, commonly known as "0" pressure printing. There will be no excessive pressure at the height of the corrugation, and the ink color of the print is soft and flat. Corrugated boxes use line printing, why use thin corrugated? Because of the high requirements of line printing, the thinner the corrugated, the more uniform the pressure

water based ink can be used in flexographic printing. Paper is interwoven with fibers, and its hydrophilicity is better than lipophilicity. Therefore, as long as you gently touch the corrugated paper, almost all the water-based ink will be absorbed by the corrugated paper, so the ink color is uniform, flat and thick. Water based ink has no pollution, low cost, quick drying and convenient operation. Flexographic printing uses a short ink path inking system with metal rollers, which can use water-based ink, which is also the feature of flexographic printing. The long ink path of lithography cannot be achieved by oily ink (oxidation drying ink)

high efficiency, high quality and high speed process technology. At present, the technological routes of corrugated box printing in China include: first, silk printing. It is suitable for transportation and packaging in small batches and with low requirements. 2、 Corrugated paper is printed by flexographic printing after forming. Because this steel bar zigzag testing machine is developed according to the national standard metal zigzag testing method (gb232 (8)) and is printed after corrugated paper is formed, the process is simple, and it can basically meet the requirements of corrugated paper printing from monochrome to multicolor line plate, so it can achieve high efficiency and high quality. Coupled with high printing speed, 350 sheets per minute for small specifications and 170 ~ 220 sheets per minute for large specifications, it is an ideal printing technology. 3、 Pre print the leaflet. This process uses a single sheet of bio based high molecular materials and renewable resources as the main raw material. Although the printing quality is high, it still uses sheet mounting corrugated, indentation, slotting and die cutting, which can not reach high speed. Moreover, there are not many large-scale lithographic presses with high cost, which limits the development. It is also starting in China. The main advantage is high printing quality. However, it is suitable for large batch packaging, and the cost is higher than that of corrugated paper printing after forming

flexo printing machine is simple in structure and suitable for enlargement. The corrugated box has a large area and a length of 1.6 ~ 3.5m. If the long ink path ink transmission system of lithography is adopted, the equipment is huge and it is difficult to manufacture, operate and maintain. The flexographic press has a simple structure, and four rollers can form a color deck. The diameter of the roller is suitable to be larger, which just meets the requirements of the printing plate roller, and can improve the mechanical accuracy and stability. Due to its simple structure and large equipment space, the machine can meet the requirements of plate installation and adjustment, and it is convenient to clean and use. It can form a linkage production line with other processes

flexographic printing can form a linkage production line with other processes, which is another major feature. Corrugated paper is heavy and labor-intensive to move one by one, which can not meet the requirements of mass production and can not form a scale. Due to its simple structure, flexographic printing machine can form a linkage production line with other processes, which greatly improves work efficiency and reduces labor intensity. At present, most corrugated flexographic printing machines are linked with indentation and slotting. For the processes of indentation, slotting, die cutting, gluing, cartoning, counting, etc. with good performance, the finished products can be directly transported to the passenger car from the machine. (to be continued)