Using Roller to Improve Corrugated Box Printing Quality

With the development of the printing and packaging industry, corrugated cartons have gradually shifted from single-phase transport packaging to display-type packaging. The demand for corrugated cartons for printing is increasing. More and more cartons manufacturing companies are faced with the need to improve the printing quality. huge stress. For customers' "over-exaggerated" printing requirements, many companies can only relinquish their orders. At present, there are mainly three ways to improve the printing quality of corrugated boxes:

a. Print plain paper first using plain printing, and then on the corrugated paper.

b. Pre-printing, that is, the web of paper is first printed on a wide-format flexographic or gravure printer, and then the entire roll of paper is sent to a corrugated cardboard line for production.

c. Improve print quality by improving the configuration of the carton ink press itself. Compared with the former two methods, this method has the lowest operating cost, the simplest process, and the most flexible processing orders. Although the degree of exquisite printing has not been able to fully achieve the effect of printing or preprinting, it has met the requirements of most carton users.

There are many factors to improve the printing quality. This paper starts with the most important roller in many factors and talks about how to use the improved technology of anilox roller to improve the printing quality.

To improve the printing quality of the carton, the most important thing is to improve the accuracy of the printing outlets.

The accuracy of outlets is measured in two ways: First, the number of printed lines. The number of lines of the printing plate is the same as that of the number of rollers. It is expressed in terms of the number of dots per unit length. The English unit is the LPI (ie, how many dots are one inch in length), and the metric unit is LPC (that is, 1 cm in length. How many outlets). It is converted to 2.54 LPI=1 LPC. The higher the number of lines, the greater the dot density. In other words, the finer the print is. The second is the size of the smallest dot in the entire print (usually expressed as a percentage of dots). In carton flexo printing, under normal circumstances, the number of lines in the same print is fixed, and the three-dimensional sense used to express the picture is the change in the size of the dot, that is, the center distance of each dot in the same color is unchanged, but the dot size Differently, there is a “smallest dot” (also called light) in the screen. The smaller the “smallest dot” is, the better the print effect is.

Different number of lines and different proportions of the "smallest dot" printing plate, the requirements for the number of roller lines are also different. In the earlier articles on the choice of printing plate and the ratio of the number of rollers, it was often suggested that the ratio of the printing plate number to the number of roller lines was 1:3.5 to 1:4. In the foregoing, we have already mentioned that the “minimum dot” of the printing plate can not be determined by the number of lines of the printing plate alone. The printing plate on the same line number has the same or different sizes of dots. Therefore, the scientific choice method is to calculate the diameter of the smallest dot and the mesh diameter of the roller separately and make a decision, or refer to Table 1:

Minimum dot

Number of printing lines LPI

The first step to improve the printing dot precision is to increase the number of grain lines. As can be seen from Table 1, plates with the same number of lines have different requirements for the number of lines because the minimum dot is different. The number of lines used in the Internet is only the “minimum requirement”. In theory, the higher the number of anilox roller lines, the better. Because the higher the number of lines of the anilox roller, we can use the higher-number plate, so that we can do it. The finer the "smallest dot". Since the higher the number of lines, the better, but now the theoretical number of engraving lines of laser engraving equipment can reach 1000 lines or even to 250 lines, 200 lines or even lower roller?

Under the same engraving conditions, the higher the line number of the roller, the smaller the amount of ink carried, and to achieve a certain color concentration, the ink volume required for the printing plate is basically constant, and the face paper of the corrugated cardboard box is rough and absorbent. Strong, the demand for the amount of ink delivered by the printing plate is very high, and the most important factor affecting the amount of ink supply is the amount of ink carried by the printing roller itself.

(to be continued)