Talk about the hottest UV offset printing process

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UV offset printing process everyone talks about

UV offset printing has incomparable advantages over traditional offset printing in terms of surface texture, protection, wear resistance and production efficiency, especially for the printing of plastic sheets, gold and silver cardboard and other non absorbent materials. These advantages make those printing enterprises that apply UV offset printing technology stand out from the competition. However, UV offset printing process is relatively complex. How do packaging and printing enterprises deal with the problems existing in the process of UV offset printing? How should packaging and printing enterprises that intend to adopt UV offset printing be prepared? In response to these problems, this paper obtained the answers through the insightful opinions of Mr. Li Zhuobin of Dongguan Hucai Printing Co., Ltd., Mr. Yang Kan, manager of the production department of Beijing colorful printing Co., Ltd., Mr. Liu Jiyang of Chengdu Jiuxing printing and packaging Co., Ltd., and Mr. Wang Wei, who has been engaged in the continuous increase of the load of u-subject packaging bags from zero for many years

uv offset printing problem solving

in order to make UV offset printing work better, the main problems that need to be solved are as follows

1. design plate making

the output format of the design draft for UV printing must be determined according to the work order, such as the forward or reverse scanning of the film surface, the number of output lines, line angle, etc. Some special prints require higher resolution, such as 3D printing, and the line angle must match the printing material to avoid collision; Transparent plastic sheet and aluminized paper often need to be printed with white ink. Pay attention to the influence of the expansion and contraction of the printing material, and correct the film in advance to achieve the best quality

2. Adhesion

<11. Deformation measurement accuracy: within ± 0.5% of the indicated value; p> Due to the poor permeability of substrates such as plastic sheets or gold and silver cardboard, and the weak adsorption of ink, even if UV ink is used for printing, the ink adhesion is also very poor, and the printing quality is not high. It can be solved by surface treatment of materials

3. ink emulsification

uv ink has a narrow tolerance of water ink balance, which is easy to cause ink emulsification and dirty version in printing, affecting the printing quality

solution: reduce the printing speed and control the printing speed at 5000 ~ 8000 prints/hour

4. curing degree

in order to improve the color saturation of printing, when UV printing is carried out on the surface of substrate such as plastic sheet, the printing pressure is large, the ink layer is thick, and the dot increases seriously, which makes the ink difficult to cure. In order to ensure the printing quality, the printing pressure can not be adjusted greatly. It is the preferred material for the cosmetics packaging industry in the future. The solution is to reduce the printing speed moderately first, lengthen the UV lamp irradiation time appropriately, and let the ink solidify completely; The second is to adjust the distance between the UV lamp and the substrate, increase the intensity of UV light irradiation, and solidify the ink. The effective wavelength range of UV curing is 200 ~ 400nm, and the wavelength of some light sources in the printing workshop is also within this range, which will lead to slight curing of the ink surface, so we should pay attention to the influence of ambient light on UV ink

5. color sequence arrangement

uv offset printing color sequence arrangement is complex. Due to the limitation of the inking principle, the ink layer on the substrate is thin. When a thick ink layer is required, the printing product is difficult to achieve the desired replication effect. For example, in four-color overprint, the commonly used printing color sequence is black, cyan, magenta and yellow. Because black almost occupies all the space, the inking power of cyan, magenta and yellow is lower, and the total amount of ink is not enough, which will cause the color to be not full

solution: change the color sequence, first print the color with a small amount of ink, and finally print the black with a large amount of ink, so as to maximize the ink amount and make the color fuller

6. printing registration

uv offset printing uses UV light to cure the ink. The main problem caused by curing is that the substrate is heated and expanded, resulting in inaccurate overprint. This is in contradiction to UV ink curing, because UV lamp irradiation time is required for ink curing, while UV lamp irradiation time is required for annealing seamless steel pipe brush sleeve with printing wall thickness less than 13mm

solution: UV curing is carried out after the last color printing. At this time, even if the substrate expands, the deformation of the substrate can be minimized by placing it for a period of time to reduce the temperature. Under special circumstances, the intermediate color group can also be illuminated with UV light, but the shorter the irradiation time, the better. Alternatively, cold UV technology can be used. For details, see printing technology, issue 385. (end)

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