Skills and troubleshooting of water-based ink for

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Corrugated board printing water-based ink skills and troubleshooting (II)

▲ 2. Troubleshooting of common faults

at present, flexible direct printing corrugated board printing is more and more widely used in the packaging industry, so the application of

water-based ink is also increasing significantly. However, due to the uneven surface of corrugated board, higher printing pressure is required, and due to the above-mentioned special properties, water-based ink will not only obtain a wide range of applicable properties, but also have some printing faults due to poor stability of the ink itself and inconsistent with the operating conditions of the printing machine

(1) gel of water-based ink

main reasons and solutions: this failure occurred during the beginning and use of water-based ink, which may be due to improper storage, that is, the ink was not sealed in a cool place. In addition, we should check the use of additives and solvents, and use specially matched additives and solvents. Check whether other inks are mixed, and pay attention to the strict confirmation of different inks before use. If the ink has serious gel, it needs to be replaced with a new ink

(2) the ideal color concentration cannot be reached

main reasons and solutions: first check the viscosity of the ink. If the viscosity is too low, replace or redeploy the original ink. As the water-based ink is prone to stratification, sedimentation and other phenomena, it should be fully shaken before use. If the ink is found to be of poor quality, it should be replaced. Check the ink transfer effect. If the transfer is poor, check the roller, printing plate, cardboard and other factors

(3) poor ink transfer

main reasons and solutions: first, check the pressure of the printing machine. If the pressure is insufficient, increase the printing pressure. Check the hardness of the printing plate by gun. If the hardness does not match, replace it. Check the hydrophobicity of the paperboard and use water-based ink with appropriate hydrophobicity. Finally, check whether the corrugated roller of the printing machine is worn or aging. If there is any problem, replace it with a new one

(4) poor overprint

main reasons and solutions: it is mainly caused by excessive printing pressure of the previous color, too high viscosity of the previous color ink and too slow drying speed of the previous color ink. It can be handled according to different situations. For example, adjust the relative pressure of various colors of printing, reduce the viscosity of the previous color, and adjust the drying speed between various colors of ink to make it match

(5) the edge of the printed image and text is not clear

main reasons and solutions: the possible factor causing this fault is that the accuracy of the printing plate is too low, so we should pay attention to the new plate making or adjust the thickness of the printing plate; The pressure between the printing plate and the embossing roller is too high, so it is necessary to adjust and reduce the pressure; The viscosity of water-based ink is too high. Adjust the viscosity of ink and try to use low viscosity water-based ink

the width of the sample should be corrected from 60mm to 50mm (6) poor drying

main reasons and solutions: first, check whether the drying performance of the water-based ink is appropriate, and it is best to use the fast

drying water-based ink; Check whether the viscosity of water-based ink is too high. If the viscosity is too high, dilute the ink again; Check the absorption performance of the cardboard. If the absorption performance is too poor, replace the cardboard with good absorption; Check whether the imprinted edge is enlarged. If it is enlarged, it is caused by improper plate pressure. Adjust the plate pressure or replace it with a new one

(7) the ideal viscosity cannot be obtained

main reasons and solutions: due to the strong thixotropy of ink, the viscosity should be measured after the ink is fully circulated

(8) ink foaming

main reasons and solutions: the main reasons for ink foaming are insufficient foam suppression ability of ink, insufficient circulation of ink and air leakage of circulating pump. The solution is to add defoamer in time, pay attention to improving the circulation of ink, check whether the circulating pump leaks, and repair it in time

(9) printing materials are not resistant to printing

main reasons and solutions: This is caused by poor water resistance, light resistance, friction resistance and other properties of ink or improper paperboard. The solution is to deal with these situations, that is, replace the appropriate ink and matching cardboard

(10) white dots and pinholes

main causes and solutions: the failure of white dots and pinholes in printed crystal graphics and texts (especially in large places on the ground) is mainly caused by excessive addition of defoamer and too thin water-based ink. Pay attention to control the dosage of defoaming additive (generally, it is appropriate not to exceed 0.2% of the total ink volume according to experience), and do not add defoaming agent in large quantities due to the failure to obtain the ideal viscosity and other reasons. For inappropriate thin ink, readjust the original ink according to the characteristics of the paperboard

(11) troubleshooting of common printing faults

common faults in corrugated board printing include: blurred paper handwriting printing; On the top of the overlapping printing, the color is pear shaped and cannot be covered evenly; There are indentations on the surface of the paperboard; The printing surface is powdery and easy to fade; After printing, the surface of the paperboard bristles. In view of the above several faults, the following measures can be taken to eliminate them - for the fuzzy printing of paper handwriting, especially the fuzzy writing of small words, this is mainly due to the excessive printing pressure, the idling of the drum, the thin ink, the corrosion depth of the printing plate or the insufficient depth of the lettering of the rubber plate. If the writing of small characters is blurred, it is due to the accumulation of ink in the text depression of the printing plate, and the hardness of the rubber plate of small characters is the same as that of large characters. The solution is: reduce the pressure, increase the ink desiccant, improve the viscosity, prolong the corrosion time of the printing plate or engrave the font of the plate deeply; At the same time, improve the stacking method after printing. For small words that are fuzzy, the printing plate should be cleaned to improve the hardness of the rubber plate. The thickness of the printing plate should be reduced by about 0.6mm. When reducing the pressure, the ink should be thinned a little with inking oil. To solve the problem that one color on the top of overlapping printing is pear shaped and cannot be covered evenly, we should increase the viscosity of the first color ink, print as thin as possible, reduce the viscosity of the second color and improve the printing pressure

the indentation on the surface of the paperboard is caused by the gap between the paper feeding rollers being smaller than the thickness of the paperboard, so the gap between the paper feeding rollers should be increased. The surface of the printed matter is powdery and easy to fade, which is mainly caused by the mismatching of the ink performance, such as too strong permeability, improper coordination with dryness, etc. In addition to reporting and seeking solutions with the ink manufacturer, it is generally necessary to replace the appropriate ink. The main causes of fuzzing on the surface of printed paperboard are poor quality of base paper or excessive viscosity of Shantou ink. Replace the appropriate corrugated base paper and reduce the ink viscosity according to the situation

the digital technology of flexographic corrugated paper printing

with the current industrial development, the high-end equipment, core chips, control systems, key materials, etc. that need to rely on imported computers and their related technologies are widely used in the printing field, so that the quality of printed matter and printing speed can be greatly improved. The computer direct plate making technology, which is widely used in offset printing, has also begun to be widely used in flexographic printing. Flexo direct plate making based on digital technology can be regarded as the latest technology of flexo printing. It can make flexo printing obtain excellent printing quality, and achieve and surpass offset and gravure printing quality in some aspects. It can be regarded as the future development direction of flexographic printing. Direct plate making process in the plate making process, oxygen will inhibit the resin chemical reaction speed, and can achieve the best balance in inhibiting the oxygen and UVA curing of special engineering plastics, especially those with the highest technical content, so as to make the point clearer and effectively control the common disadvantages of increasing the midpoint of flexo printing. Using the hard compression pad servo valve as the tool material often used by the experimental machine can obtain excellent line image printing effect. Compared with the traditional flexo plate making technology, it can reduce the dot increase by 15% - 25%. Using digital plate making as the pre printing process of corrugated boxes can also make flexographic prints colorful and clear images

(author/Lin Qishui)

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