Analysis of Factors Affecting the Expansion of Corrugated Box Flexo
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Although the use of flexo in corrugated boxes started late in China, there are many advantages in flexographic printing, including the reduction of the price of flexographic plates, the rapid plate making speed, the fast drying of ink, the good printing durability and the damage to corrugated cardboard. As well as no environmental pollution, etc., the development is very rapid, and the use in carton production is now quite common. At present, corrugated boxes have changed from simple transportation packaging to sales packaging, and customers' requirements for printing are gradually increasing. In order to increase the amount of consumption, in order to save costs, the requirements of corrugated box printing on the degree of design reduction are naturally higher and higher. This requires corrugated box printing not only for simple text printing, but also for complicated dot grading and large format. Field printing.
In production, flexographic printing does not have much problem in the use of text and color blocks, but in dot printing, it is often plagued by dot expansion. The specific performance is: corrugated printing is obvious. The main reason for this is that the flexographic plate has a limited hardness (34?0 degrees), which is caused by the expansion of the dots during compression. This is also determined by the inherent characteristics of the flexographic plate, because the flexographic plate is soft, and deformation under a certain pressure is its characteristic. In the printing, the printed surface of the corrugated cardboard is not flat, and the deformation of the flexographic plate enables the printing plate and printing. The face is in full contact to achieve the transfer of ink from the plate to the corrugated board. In actual production, it is impossible to eliminate the expansion of the dot, and it is only possible to control the dot expansion by reducing its deformation.
To control the expansion of outlets will involve the following aspects of corrugated box production.
Paper (face paper)
■Paper absorption
Corrugated boxes are basically printed with water-based inks. The ink is combined with the paper by penetration and evaporation. If the water absorption of the paper is not good, the ink is difficult to bond with the paper.
■ Paper moisture
In general, the effect of paper moisture on printing is not obvious. However, when the paper moisture is too high, the drying time of the ink is prolonged, and the spread of the dots causes the visual effect to be unclear. Multi-color dot overprinting has a large color deviation.
■Coated paper
At present, coated paper is more and more used in corrugated boxes, and the poor water absorption of the coated paper may cause difficulty in ink penetration, prolonged drying time, and more ink particles remain on the surface of the paper, which requires an increase in the combination of ink and paper. Sex, improve volatility, speed up drying of the ink by blowing or heating.
■ gram weight
The weight of paper has a great influence on the degree of dot spread. For the use of different enamel shapes (A, B, C, E), the grammage requirements are not the same. In general, the higher the gram weight, the less obvious at the peak spread and the valley. In order to achieve a reduction in dot spread, the weight of the paper needs to be higher.
The difference in the shape of the dome is different for the degree of diffusion of the dots, and the higher the shape of the corrugation, the greater the degree of influence. Corrugated board should pay attention to maintain the height of the corrugated board when drawing, the glue should be as little as possible, the temperature of the hot plate is high enough, the board is flat and there is no dew.
Ink
The effect of ink quality on printing is critical, and it is best to use low viscosity, high color density inks for dot printing. At present, an alkali-soluble resin system ink is generally used, which has a certain basicity, and mainly relies on an ammonia-based volatile substance to dissolve the resin in water. Attention must be paid to the viscosity, pH value, drying speed, etc. of the ink. The dot printing requires low ink viscosity, fast drying and good ink resolubility. It is best to use higher grade inks when printing dots, and use special water-based dot inks if necessary. When printing on multi-color overprint dots, you may encounter such a situation: on the one hand, the underlying ink is not dry enough, and on the other hand, since the tissue has absorbed the moisture of the underlying ink, the water absorption is lowered, resulting in ink on the overprint. Infiltration, resulting in dot spread. This phenomenon requires adjustment of the ink pH and drying speed in the color sequence of the printing. In actual production, the use of ink is quite complicated, and the ink supplier can be assisted if necessary.
Plate
■Selection of film
For fine dot printing, film films need to use better quality products. For the printing of high-demand dot printing, the domestic film film is difficult to achieve the expected results, and only the foreign film film with high price and high quality can be selected.
■Selection of plate material
The resin plates have different hardnesses, and the dot spread is mainly caused by the expansion and deformation of the dots on the printing plate under pressure. In order to reduce the dot, it is a solution to choose a plate with a higher hardness. However, in actual use, the deformation of the plate is too small and the bottom of the valley is partially exposed. In order to eliminate this phenomenon, it is necessary to increase the platen roller. The pressure, but at the same time this will increase the deformation of the plate. Therefore, the choice of plates needs to be carefully considered. There is currently a liquid version, its biggest advantage is that it can make the top of the plate dot hardness higher (hardness can be selected in 36? 2), and the base part can choose less hardness, the company where the author has tried, The effect is obvious.
■Network selection
There are many kinds of mesh points, and the dot used on the plate with a hardness of about 36 degrees is better according to the author's own experience. The square and diamond shape are obviously deformed during use, and it is prone to dot spread or even dot adhesion. The phenomenon. Sometimes, the customer designer does not take into account the actual situation of the corrugated box, there may be a series of problems.
■ Carton design
Since there are few professionals in carton design, many corrugated carton printing designs are provided by customers, and the customer's design draft is designed by the advertising company or directly by offset printing. Therefore, the carton supplier is required to produce, which will definitely not appear. Less problem. For example, the color requirements are too high, the number of dot lines is too high, the highlights are too high (the dots below 3% cannot be guaranteed, and may be lost), and the vector and bitmap relationship processing is difficult to fit the production of corrugated boxes. Therefore, the design of the carton requires the carton supplier to have a professional designer or a professional plate maker to complete.