Analysis and Thinking on the most popular corrugat

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Analysis and thinking of corrugated board flexographic printing (Part I)

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. Flexible printing technology is adopted for corrugated boxes, accounting for about 95% in the United States, 85% in Western Europe and more than 93% in Japan. It is gradually accepted by corrugated box manufacturers in China. In recent years, it has developed rapidly. It is estimated that more than 50% of the enterprises using this technology before the completion of 300KN are now using corrugated board multi-color flexographic printing slotting machines

1. characteristics of flexographic printing

corrugated board flexographic printing has the following advantages: flexographic printing can not only copy the ground version that can meet the experimental measurement needs of different materials, but also copy the line version; Corrugated paper printing has developed from monochrome and two-color to multi-color line version, which has changed the situation of monotonous ink color and simple graphics and text in the past, and met the requirements of sales packaging. This is an inevitable law of development. At present, line plates are printed on corrugated paper (boxes and boxes), 100 lines/inch can be printed on e corrugated paper, and 40 lines/inch can be printed on a, B and C corrugated paper. Flexo can make both field version and line version, meeting 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 the corrugated paper with its own compression elastic deformation during 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 the bad film. The flexographic plate can compress and deform, which is absolutely impossible for flat printing and gravure printing. Therefore, the thickness of the flexographic plate used on corrugated boxes is relatively thick, generally mm, while the thickness of the flexographic plate used for flexible packaging printing is only 1.14mm and 1.7mm. The reason why thick plates should be used on corrugated paper is to use its compression deformation. Now in order to reduce the cost, 4mm plates and 3mm air cushion rubber lining (plastic lining is not allowed) are used for better effect. Of course, we should advocate that the thickness and quality of corrugated paper should be basically the same. 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 can not contact the printing plate, and the ink can not be printed. Therefore, both flat printing and gravure printing can not 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 corrugated, and the ink color of the printed piece is soft and flat. Corrugated boxes use line printing, why use thin corrugated? Because the upper and lower jaws are required to be tightened for line printing, the thinner the corrugated, the more uniform the compression

water based ink can be used for flexographic printing. The paper is interwoven with fibers, and its hydrophilicity is better than its lipophilicity. Therefore, as long as the paper is gently contacted with 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. The water-based ink has no pollution, low cost, quick drying and operation. Flexographic printing uses a short ink path inking system with metal roller, 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 with small batch and low requirements. 2、 The corrugated paper is printed by flexographic printing after forming. As the corrugated paper is printed after forming, the process is simple, and can basically meet the requirements of corrugated paper printing from monochrome to multi-color line version, so it can achieve high efficiency and high quality. In addition, the printing speed is high, with 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 of single sheet. Due to the use of sheet fed lithographic printing line plate, although the printing quality is high, this process still uses sheet mounted corrugated, then indentation, slotting and die cutting, which can not reach high speed. In addition, there are not many large-size 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 transfer system for 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 enlarged, 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 is easy to clean and use

flexographic printing can form a linkage production line with other processes, which is another major feature of flexographic printing. 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 flexo printing machines are linked with indentation and slotting. For the processes of indentation, slotting, die cutting, gluing, box making, counting, etc. with good performance, the finished products can be directly transported to the passenger car from the machine

2. relevant requirements for flexographic printing

comply with the automotive interior standard (1) the printing plate

corrugated board has a certain elasticity in the direction perpendicular to the paper surface, which has a cushioning effect on the packaging. This is the main reason why corrugated board is widely used to make packaging boxes. But this elasticity brings some difficulties to printing. In order to adapt to the flexible printed matter and make it have good ink transfer, the printing plate must be softer than the printing plate used in general flexographic printing. Except for particularly fine prints, the plate hardness of most corrugated boards is 30 ± 5 shore

(2) brush machine

corrugated board flexographic printing machine has a variety of specifications, and the small one can print 610 mm × 1620 mm corrugated board, up to 2030 mm large × 4830 mm。 Because the printing format is very large, the plate cylinder is also very large. Generally, the plate cylinder cannot be disassembled. When printing a new job, the flexible plate on the plate cylinder can be replaced

the corrugated board has enough stiffness, so in order to adapt to the substrate with a certain stiffness, the paper feeding system of the corrugated board printing machine adopts the single sheet feeding method. The paper feeding condition is to push the end of the paperboard into a pair of paper feeding rollers, so as to feed paper to the imprinting part. During the whole paper feeding and printing process, the corrugated board passes through the printing machine on a horizontal plane

corrugated board can be printed by a single machine, but now many carton factories often combine the printing process of corrugated boxes with the equipment of other processes of cartoning to form a cartoning production line. For example, printing, slitting, molding, folding, gluing, bonding, labeling, binding, etc

(3) ink

most corrugated boards are printed with water-based ink. This is because: first of all, the text or simple patterns printed on the corrugated board do not need high gloss (only for the quality requirements of some cartons), and the water-based ink can meet the printing quality requirements. Secondly, corrugated board is a loose fabric with strong water absorption. After coating with water-based ink, its drying method is mainly penetration drying, with fast drying speed, and there is no need to set a drying device. Again, water-based ink pollution, low cost. (to be continued)

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