Our company is a printing company mainly consisting of cigarette packs and medicine boxes. With the development of China's packaging and printing industry, and the extensive application of flexographic printing in packaging and printing, in order to improve the efficiency of enterprises and protect the environment, our company has introduced two Pioneer 1800 models from the US Tangsman Company from 1996 to 1998. Seven-color, eight-color flexo printing production line.
Flexo printing is pollution-free green printing, and it is developing rapidly. Its scientific and technological content also continues to increase. For us now, the study of new technologies and processes for flexographic printing began. In order to master the new process of flexo printing, we spent a longer period of time learning and exploring, and the operation of the equipment went into normal. After several years of continuous practice, under the guidance of relevant experts and peers, we have gradually mastered this process technology and formed a set of effective operating experience. In recent years, the quality of products has been stable, consumption has declined, and customers have been satisfied. The company has also achieved good economic benefits. As with other printing methods, flexo printing is to obtain prints with smooth ink, rich layers, and vivid colors. However, the flexographic printing process is light pressure printing, and the key is the strict matching of the printing machine's embossing structure, printing roller, plate material, anilox roller, double-sided adhesive, ink and other conditions. However, it is difficult to adjust many variable parameters between them to the optimal point. Through years of exploration and practice, we have the following experience.
1 Process from the manuscript to the printed product
In early 1998, we successively printed the “Ocean” brand, gold card, and cigarette packs of Guizhou Chiyu Group. The samples we obtain are proofs of lithographic printing. To achieve faithful reproduction of printed samples and originals, the process features that are suitable for flexo printing are more difficult. Among them, the “Ocean” brand cigarette pack manuscript is a red solid stripe stencil of small prints and a dot-sailing pattern. In practice, we recognize that due to the differences in lithographic and flexographic printing processes, dots, text, and lines of the same color cannot be used in the field. On the same color version, this is because the dots are different from the ink required in the field. If it is done on the same plate, after the anilox roller has passed the ink quantitatively, it will not be able to meet the amount of ink needed in the field, and vice versa. Therefore, we separate the same hue from the field. The large area patterns of the two stacked versions are the same. Genuine with a naval sailboat pattern, equipped with a 500-line anilox roller, remove the naval sailboat pattern on the sub-version, and enlarge the edge of the stenciled small print by 0.1mm, equipped with a 360-line anilox roller, which not only avoids the fine print " Paste version "broken pen, but also to the full, bright effect of the field.
Due to a variety of reasons, the product cannot be processed on the flexo printing machine in a single line. We have made ladder-type information lines in the horizontal and vertical directions of each batch of products printed as the cutting standard to ensure that In the production process, the cross-sections are precisely controlled to create the necessary conditions for the successful execution of the bronzing, embossing and die-cutting operations in the next process.
There are a lot of high-grade and fine products in cigarette pack prints. It is difficult to print and the quality consistency among batches is high. The difficulty in the production of flexo printing is that the accuracy of overprinting accuracy is relatively large, which affects the accuracy of post-process bronzing, embossing, and die cutting. The round-press printing method will cause cumulative errors due to continuous rolling, coupled with factors such as machine vibration, personnel operation differences, and raw material quality, the accuracy of overprinting cannot be maintained. These conditions must be known and adjusted in a timely manner. Experience and propose feasible solutions.
2 Material selection and reasonable use
1 Anilox roller. The anilox roller is an important part of the flexographic printing machine. It is used in conjunction with the squeegee blade to accurately and evenly deliver the water-based ink. In order to ensure the quality of printed products, our company has configured more than 60 anilox rollers with 200 to 800 lines. This has created a wide space for the selection of matching plates and patterns. In actual operation, the same number of anilox rollers must be selected, numbered, and detailed records of the use of the same number of lines must be cleaned before and after the machine. This will not only stabilize the quality of the print but also protect the anilox roll.
2 water-based ink selection. At present, the brand, quality, and price of flexo-printing inks vary, and the range of applications for printing materials is also very wide. How to match them is also a matter of caution. We have learned from this experience. In 1998, when we printed the "Golden Bear King" brand, gold card, and cigarette pack of Guizhou Huangguoshu Group, we did not consider that the gold card paper is non-adsorbing paper, which may affect the problem of ink consumption, thus causing problems such as deinking, stencil printing, etc. . Afterwards, we selected trials such as “Walik”, “Aksu Nobel”, and “Tianshi” for ink. The experience gained was:
● Understand the adaptability between the ink and the printing material. After the two are matched together to obtain the best effect, it is the object of choice.
● Pay attention to the viscosity and pH value of the stable aqueous ink at any time in the printing process, and control the dosage of the auxiliary agent, and timely adjust the drying performance.
● It is the responsibility of the person who dispenses the ink to make a good record of the above ink conditions and maintain the good adaptability of the ink.
3 Actual precautions
The actual operation is the most concrete production process that seriously implements the process technology standards. In addition to the original operating procedures and post responsibility system, our factory also summarized its experience.
1 Prepress equipment inspection and loading. Lubricate all transmission parts before printing. All fastening parts must be locked. Check the plates carefully and paste them carefully. The two lenses on the platen must be in the same horizontal position. The angles of the left and right cross-hairs on the screen should be the same. Special attention should be paid to the flatness between the three-sided adhesive, the platen roller, and the printing plate to avoid bubbles and influence the flatness of the pressure. Generally, one set of printing plate is installed by one person. When two people simultaneously install a set of plates, different sizes of force will lead to different loading effects, which will affect the accuracy of overprinting.
2 pressure adjustment and tension control
In order to ensure the accuracy of the overprint, it is very important to adjust the pressure of the machine. To this end, we have taken measures to match the number of shafts and plate bearings and the printing units. In addition, try not to use a larger version of the roller, to avoid the large diameter caused by the imprinting, affecting overprinting and reduction of printed products.
Flexographic printing is light pressure printing, and its process determines the importance of pressure regulation in actual operation. Due to the elasticity of the printing plate, it is critical to achieve precise positioning of the pressure adjustment between the anilox roller, the printing plate roller, and the embossing roller. In order to understand this problem, we created two information bars on both sides of the plate to determine the pressure is uniform, observe the changes in the information bar, and pay attention to changes in the speed of the equipment during operation. The effect of machine vibration on pressure is adjusted immediately.
Paper tension control. The web must maintain a certain tension during the printing process. The magnitude of the tension control value should be adjusted according to the thickness of the printing material and the width of the printing material. After the printing speed is normal, the same roll of paper must maintain the tension and the tension on both sides of the roll must be the same. In this way, it is possible to avoid ink “pulling” and overprinting.
3 After finishing a print, the anilox roller and printing plate should be cleaned in time, the remaining water-based ink should be kept sealed, the ink on the platen shaft seat should be wiped off, the engine oil must be applied, and lubricant should be applied to the transmission parts to keep the equipment and the environment clean. clean. (author; Tao Xiaoyang)
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