Although the use of flexible plates in corrugated boxes started later in the country, there are many advantages in flexographic printing, including the decreasing price of flexographic plates, fast platemaking speed, fast drying of ink, good printing performance, and small damage to corrugated cardboard. As well as environmental pollution, etc., the development is very rapid, and the use in carton production is now quite common. At present, corrugated cartons have changed from simple transportation packages to sales packages, and customers' requirements for printing are gradually increasing. Manufacturers in order to increase the amount of customers in order to save costs, the corrugated carton printing the design of the degree of reduction is naturally higher and higher, which requires the printing of corrugated boxes not only have a simple text printing, but also have a complex dot gradient and large format The field printing.
In the production, flexo printing does not have much problem in the use of text and color blocks, but it is often plagued by dot expansion in dot printing. The concrete manifestation is that corrugation is obvious. The main reason for this is the limited hardness of the flexo (34?0 degrees), and the expansion of the outlets during compression. This is also determined by the intrinsic properties of the flexographic plate, because the flexographic plate is soft and deformed under certain pressure is its characteristic. In the printing, the printed surface of the corrugated cardboard is uneven, and the deformation of the flexographic plate can make the plate and printing. The surface is fully in contact to achieve ink transfer from the plate to the corrugated board. It is impossible to eliminate the expansion of outlets in actual production, and control network expansion can only be achieved by reducing its deformation.
To control the expansion of outlets will involve the following aspects of corrugated box production.
â– Paper absorbency
The printing of corrugated boxes is basically water-based ink. Ink is combined with paper by penetration and volatilization. If the water absorption of the paper is not good, the ink will be difficult to combine with the paper, causing the paper surface to have a î‰© î‰© î‰© è¯º è¯º î–î†§ è¯º è¯º èš§åµ© èš§åµ© èš§åµ© èš§åµ© èš§åµ© èš§åµ© èš§åµ© èš§åµ© èš§åµ© è›”æ‚–îƒ¨î‰ˆæƒšå’´ è›”æ‚–îƒ¨î‰ˆæƒšå’´ è›”æ‚–îƒ¨î‰ˆæƒšå’´. î€”å—çª’èž…îƒ°åº è¯™å—Œî‚Šî‰ˆæ„•î’šâˆˆä¿æ¶¿é£¨æ¶¿é£¨BR?BR>
â– Paper moisture
In general, the impact of paper moisture on printing is not obvious. However, when the moisture content of the paper is too high, the drying time of the ink may be prolonged, resulting in the diffusion of the dots causing the visual effect to be unclear. Multi-color dot overprinting can cause large color deviations.
At present, more and more coated papers are used in corrugated boxes. However, the poor water absorption of coated papers can cause ink penetration difficulties, prolonged drying time, and more ink particles remaining on the surface of the paper. This requires an increase in the combination of ink and paper. Sex, improve the volatility, speed up the drying of ink by blowing or heating.
The weight of paper has a great influence on the proliferation of outlets. The grammage requirements for different types of paper (A, B, C, E) are different. Generally speaking, the higher the grammage, the less pronounced the spread of the peaks and the valleys are. In order to achieve a reduction in the proliferation of outlets, it is necessary to increase the weight of the outlets.
The difference in shape is different for the spread of outlets, and the higher the level of corrugation, the higher the corrugation. Corrugated board should pay attention to maintain the height of corrugated pipe, glue should be as few as possible, the hot plate temperature is high enough, the paperboard is flat, there is no exposed phenomenon.
The effect of ink quality on printing is crucial. For dot printing, inks with low viscosity and high color density are preferred. At present, the alkali-soluble resin system ink is generally used, and has a certain degree of alkalinity, and is mainly based on ammonia-based volatile substances to make the resin soluble in water. In the use of ink must pay attention to the viscosity, PH value, drying speed and other aspects, dot printing requires low ink viscosity, fast drying, re-inking better. It is best to use higher grade inks when printing dots, and use special aqueous dot inks when necessary. When printing on multi-color printing dots, you may encounter such a situation: On the one hand, the background ink is not dried enough, on the other hand, because the surface paper has absorbed the moisture of the background ink, the water absorbency decreases, resulting in the ink on the overprint. Infiltration, proliferation of outlets. Produce this kind of phenomenon needs to adjust ink PH value, drying speed according to printing the color order. The use of ink in actual production is quite complex and can be requested by the ink supplier if necessary.
â– Film selection
For fine dot printing, films need to use better quality products. For demanding dot-printing, domestic film is hard to achieve the desired effect, and only high-quality foreign films can be selected.
â– Selection of media
The resin plate has different hardness, and the dot diffusion is mainly caused by the expansion of the dots on the plate under the pressure. In order to reduce the number of dots, the use of a harder plate is a solution, but in actual use, the deformation of the plate is too small and the bottom of the bowl is partially exposed. In order to eliminate this phenomenon, it is necessary to add a platen roller. The pressure, but at the same time it will increase the deformation of the printing plate. Therefore, the choice of media needs careful consideration. At present, there is a liquid version, its greatest advantage is that it can make the top of the printing plate dot to have a higher hardness (the hardness can be selected at 36?2), and the matrix part can be chosen to have a lower hardness, and the author's company has tried it. The effect is obvious.
â– Choice of outlets
There are many kinds of dot shapes. The dot used on the plate with a hardness of about 36 degrees is based on the author's own experience that the circle effect is better. The square shape and the diamond shape are obviously deformed in use, and dot dot diffusion or dot adhesion is prone to occur. The phenomenon. Occasionally, the customer's designer does not consider the actual condition of the corrugated box, a series of problems may arise.
â– Carton design
Due to the current shortage of carton design professionals, many corrugated box printing designs are provided by customers, and customers' design drafts are designed by advertising companies or are designed directly with offset printing. Therefore, carton suppliers are required to produce. This will certainly not occur. Less problem. For example, there are too many color requirements, the number of dot lines is too high, and the highlight part is too high (the dots below 3% are not guaranteed and may be lost). Vector and bitmap relations are difficult to handle in the production of corrugated boxes. Therefore, the carton design requires that carton suppliers have professional designers or need professional plate makers to complete.
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