Analysis on the influencing factors of flexo dot e

Analysis on the influencing factors of the expansion of corrugated box flexographic printing point

although the use of flexographic printing in corrugated boxes started late in China, it has developed very rapidly because of its many advantages, including the decreasing price of flexographic printing, fast plate making speed, fast ink drying, good printing resistance, little damage to corrugated board and no environmental pollution. Now it is widely used in carton production. At present, corrugated boxes have changed from simple transportation packaging to sales packaging, and customers' requirements for printing are gradually improving. In order to increase consumption and save costs, manufacturers and customers naturally have higher and higher requirements for the reduction degree of design at the end of the operation of tile 6 and mortar tensile testing machine. This requires corrugated box printing not only to have simple text printing, but also complex point gradual change and large format field printing

in production, there are not many problems in the use of flexographic printing on words and color blocks, but in dot printing, it is often troubled by dot expansion, which is manifested in the obvious corrugated printing. The main reason for this is that the hardness of the flexo is limited (34? 0 degrees), and it expands at the point of compression. This is also determined by the inherent characteristics of the flexo, because the flexo is soft, and deformation under certain pressure is its characteristic. In printing, the printing surface of the corrugated board is uneven, and the deformation of the flexo can make the printing plate fully contact with the printing surface to achieve the transfer of ink from the printing plate to the corrugated board. In actual production, it is impossible to eliminate the point expansion. You can only achieve the control point expansion by reducing its deformation by accepting my invitation

the expansion of control points will involve the following links in corrugated box production

paper (face paper)

■ paper water absorption

corrugated box printing is basically water-based ink. Ink is combined with paper through penetration and volatilization. If the water absorption of paper is not good, it is difficult for ink to combine with paper

■ paper moisture

generally speaking, the influence of paper moisture on printing is not very obvious. However, when the moisture content of the paper is too high, the drying time of the ink will be prolonged, resulting in point diffusion and unclear visual effect. Multicolor dot overprint will cause large deviation of colored image

■ coated paper

at present, coated paper is used more and more in corrugated boxes. The poor water absorption of coated paper will cause difficulty in ink penetration, prolonged drying time, and more ink particles remaining on the paper surface. This requires increasing the combination of ink and paper, improving volatility, and accelerating the drying of ink through blowing or heating

■ gram weight

the gram weight of paper has a great influence on the degree of point diffusion. The requirements for the gram weight of facial paper used in different ridge shapes (a, B, C, e) are different. Generally speaking, the higher the gram weight, the less obvious the point diffusion at the ridge peak and ridge valley. In order to achieve the reduction of point diffusion, the gram weight of facial paper needs to be higher

the corrugation will increase the friction of the pendulum shaft bearing, and the degree of influence on the diffusion of points is also different. The higher the corrugation, the greater the degree of influence of the corrugation. When drawing corrugated board, attention should be paid to maintaining the height of the corrugated board, the glue should be as little as possible, the hot plate temperature should be high enough, and the board should be flat and free of corrugation

ink

the influence of ink quality on printing is crucial. It is important after setting. For dot printing, it is best to use ink with low viscosity and high color concentration. At present, alkali soluble resin system inks are generally used, which have a certain alkalinity. Ammonia volatile substances are mainly used to dissolve the resin in water. When using, we must pay attention to the viscosity, pH value, drying speed and other aspects of the ink. Dot printing requires low viscosity, fast drying and good re solubility of the ink. It is best to use high-grade ink at the printing point, and special water-based ink can be used when necessary. When printing multi-color overprint points, you may encounter such situations: on the one hand, the base color ink is not dry enough, on the other hand, because the surface paper has absorbed the moisture of the base color ink, the water absorption decreases, resulting in the penetration of the ink on the overprint, resulting in point diffusion. To produce this phenomenon, we need to adjust the pH value and drying speed of the ink according to the color sequence of printing. In actual production, the use of ink is quite complex, and if necessary, you can ask the ink supplier for help

printing plate

■ film selection

for fine dot printing, film needs to use products with better quality. For dot printing with high requirements, domestic films are difficult to achieve the desired effect, and foreign films with high price and quality can only be selected

■ selection of plates

resin plates have different hardness, and point diffusion is mainly caused by the expansion and deformation of points on the printing plate under pressure. In order to reduce points, it is a solution to choose a plate with high hardness, but in actual use, the bottom of the ridge valley will be exposed due to the small deformation of the plate. In order to eliminate this phenomenon, it is necessary to increase the pressure of the imprinting roller, but at the same time, it will increase the deformation of the printing plate. Therefore, the choice of plate material needs careful consideration. At present, there is a liquid version. Its biggest advantage is that it can make the top hardness of the printing plate point higher (the hardness can be selected at 36? 2), and the matrix part can choose the one with smaller hardness. The company where the author works has tried it, and the effect is obvious

■ selection of points

there are many shapes of points. According to the author's own experience, the points used on the plate with a hardness of about 36 degrees have a better circular effect, and the square and diamond have obvious deformation at the midpoint of use, which is prone to point diffusion and even point adhesion. Sometimes, customer designers may have a series of problems without considering the actual situation of corrugated boxes

■ carton design

at present, there are few professionals in carton design. Many corrugated carton printing designs are provided by customers, and the design drafts of customers are designed by advertising companies or designed directly by offset printing. Therefore, carton suppliers are required to produce, which will certainly cause many problems. For example, there are too many color requirements, the number of dots and lines is too high, the highlight part is too high (points below 3% cannot be guaranteed and may be lost), and it is difficult to adapt to the production of corrugated boxes in terms of vector and bitmap relationship processing. Therefore, carton design requires carton suppliers to have professional designers or professional plate manufacturers to complete