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. With regard to the “excessive†printing requirements that customers constantly put forward, many companies can only relinquish their orders. At present, there are mainly three ways to improve the printing quality of corrugated boxes:
1. First use offset printing to print face paper, and then reapply on corrugated paper.
2, pre-printed. That is, the web of paper is first printed on a gravure press of a wide web flexographic printer, and then the full roll of paper is sent to a corrugated cardboard line for production.
3. Improve the printing quality by improving the configuration of the carton ink printer itself. Compared with the former, this method has the lowest operating costs, the simplest process, and the most flexible processing orders. Although the degree of exquisite printing can not fully achieve the effect of offset printing or preprinting, it can meet the requirements of most carton users.
To improve the quality of printing, there are many factors. This article starts with the most important anilox roller among many factors and talks about how to use the improved technology of anilox roller to improve the printing quality.
To improve the quality of the carton, the most important thing is to improve the accuracy of the printing outlets. The accuracy of the dot is measured in two ways: first, the number of lines in the printing plate, the number of lines in the printing plate and the number of lines in the anilox roller, and the number of dots in the unit length. The inch system is LPI (one inch). How many dots are there in length? The metric unit is L/CM (the number of dots in a centimeter length). It is converted to 2.54 LPI=1L/CM. The higher the number of lines, the greater the dot density, in other words, The finer the entire print, the second is the size of the smallest dot in the entire print (usually expressed as a percentage of dots, which is often overlooked, but it is very important). In carton flexo printing, under normal circumstances, the number of lines in the same printed matter is fixed. The dimensionality of the dots used to express the picture is the change in the size of the dots, that is, the center distance of each dot in the same color is the same but the dot size is different. Thus, with the "smallest dot" (also called "highlight dot") in the picture, the smaller the "smallest dot" is, the better the effect of the printed matter is.
Using different number of lines and different proportions of "smallest dot" printing plates, the requirements for the number of anilox roller lines are different. In the early articles on the selection of printing plates and the number of anilox roller lines, it was stated that the ratio of the number of printing plate lines and the number of anilox roller lines was 1:3.5 to 1:4, and it was later proposed to be 1:4.5. Then someone later proposed that 1:6, 1:7,... Which one is right? In fact, the reason why the number of lines is to be studied is because the mesh of the anilox roller cannot be larger than the "smallest dot" on the printing plate. If the mesh of the anilox roller is larger than the printing dot, the plate and the anilox roll When contacted, the outlets will enter the mesh, the perimeter of the outlets will bring ink and cause the printing outlets to expand or even paste. In the foregoing, we have already mentioned that the “minimal outlets†of the printing plate are not only the lines of the printing plate. The number will be able to determine, the same number of the same version of the Internet point of the printing plate is very large and small, so the scientific choice is to calculate the diameter of the smallest dot and the mesh diameter of the anilox roller.
The first step to improve the printing dot precision is to increase the number of anilox roller lines. It can be seen from the above table that the minimum number of dots on the same plate line is different for the number of lines of the anilox roller. The number is only the "minimum requirement". Theoretically speaking, the higher the number of anilox roller lines, the better, because the higher the number of lines of the anilox roller, the higher the number of lines can be used to make the finer "minimum dots". ". Since the higher the number of lines, the better, and now the theoretical number of engraving lines of the anilox roller laser engraving equipment can reach 1000 lines or even to 2540 lines, why most manufacturers are still using 250 lines, 200 lines or even more Low anilox roller?
Under the same engraving conditions, the higher the number of lines of the anilox roller, the smaller the amount of ink carried, and to achieve a certain color density, the amount of ink transferred by the printing plate is basically constant, and the face paper of the corrugated cardboard box is rough and absorbs water. Strong, strong demand for the ink volume delivered by the printing plate, and the most important factor affecting the ink supply is the amount of ink loaded by the anilox roller itself.
The amount of ink is mainly determined by the engraving method. Currently, the laser used to sculpt the ceramic roller used for corrugated box printing is only CO2 and ULTRACELL. (The YAG laser cannot engrave the mesh of the low-mesh line, and when one engraving length exceeds one Above the meter, the strength will be unstable, so it can not be applied to the anilox roller on engraving carton.) The anilox roller engraved by CO2 laser is of V type, and the effective ink carrying capacity is too small. If the ink value is continuously carved in depth, not only the ink in the depth of the mesh cannot be transmitted, but it becomes an “invalid ink-carrying amountâ€, and it also affects the quality of the anilox roller; secondly, the CO2 laser-engraved anilox roller The surface is rough, the tension is small, and the ink's transmission is poor. The 250LPI roller made by the better technical anilox roller manufacturer can meet the requirements for the ink volume of the printing area and the dot network. The 250LPI roller with the poor technology can only be used for printing dots, and the field version must use 220 points. Even lower line counts (referring to printing on general cartoned paper).
Therefore, we believe that through the improvement of the number of lines of the anilox roller and the replacement of the engraving method, the flexographic printing will be more suitable for the needs of the packaging and transformation of corrugated paper and truly achieve the goal of both printing quality and printing efficiency.
Corrugated paper printing for packaging transformation: technical improvement of anilox roller
August 12 03:00:39, 2024
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