Technical design and key points of composite flexible packaging The design of composite flexible packaging is the first step in the design and manufacture of composite flexible packaging. Unreasonable design of the document will increase the difficulty of printing and reduce the yield of printed products. It may also result in difficulties in processes such as slitting and bag making. , Or even cause the entire batch of products to be scrapped. There are generally two types of manuscript design for composite flexible packaging. One is artistic design, and the other is technical design. Artistic design is an art problem. This article mainly discusses technical design and plate making.
First, the design of the electric eye cursor
Positioning heat sealing and positioning cutting are often performed during the automatic packaging of bag or composite webs, and an electric eye cursor needs to be set in the document for positioning. The eye can be placed at the bottom of the bag when designing, which is more beautiful. The electric eye cursor can be unilaterally on the coil or bilaterally. However, it is recommended that there be bilateral, so that it can avoid the use of existing coils on the left side of the eye of the coil. Some need to constantly adjust the position of the photoelectric eye. The size of the cursor also has certain requirements, and there are certain differences in different packaging opportunities. General requirements of the cursor's width is greater than 2mm, less than 10mm, length greater than 5mm. The width of the cursor (less than 2mm) may be due to the weak signal, affecting the normal tracking of the device. The cursor is too wide (greater than 10mm). On the one hand, it is unsightly. On the other hand, it also causes the tracking positioning accuracy to decrease. The length of the cursor should generally be greater than 5mm. In the packaging process, the roll film will shake and deviate. If the cursor is too short, the cursor may deviate from the position of the photocell, and the cursor cannot be traced.
The cursor is generally selected to have a dark contrast with the background color, preferably black, and generally cannot use red and yellow as the cursor, nor can the color of the same color as the photoelectric eye be used as the cursor color, such as the glow of the photoelectric eye is green. Light, you can not use the light green color as the color of the eye sensor, because the green photoelectric eye can not recognize the green color. If the background color is a darker color (such as black, dark blue, deep purple, etc.), the cursor should be designed as a hollow, light-colored cursor.
For bag making machines, there is generally a microcomputer-controlled electronic eye tracking system with a fixed length. It can choose the photoelectric eye signal within a certain position range to be effective (general signal within fixed length ± 3mm is effective) ,And in this range of words and patterns can be "invisible", so you can not design the cursor. However, care should be taken to use traces that are too small or too short for trace points, or arc- or diagonal-shaped traces. If there are no suitable trace points, cursors must be designed.
The electrical eye system of a typical automatic packaging machine is a simple identification system. Can not have the function of intelligent fixed length as the bag making machine, so in the range of vertical electric eye cursor does not allow any interference of text and patterns, or disturb the text and patterns in the packaging process equipment will be mistaken for the electric eye cursor, Causes identification errors, of course, some high sensitivity of the electric eye, the black and white balance can be finely adjusted, for some light-colored interference signals can be removed by adjustment, but the color and the cursor is similar to or darker pattern interference signal can not be removed .
The distance between the cursors is used to set the length, and the error between the actual spacing and the design value cannot be too large. Generally only ±0.5mm error is allowed. For many automatic packaging equipment, the negative deviation is better than the positive deviation, so it is recommended that the design be negative. For some automatic packaging machines, they can work normally only when the distance between the cursors is a negative deviation. There are very few automatic packaging machines that not only require negative deviations between the distances between the cursors, but also have high precision requirements, such as vacuum adsorption tracking by Germany Siebler Company. The automatic packaging machine that is being dropped requires that the error between each cursor does not exceed: -0.02, -0.08.
Aluminizing or pure aluminum has strong specular reflection, which will affect the recognition of the electric eye. It is recommended that the compound film mark be printed with a white background. For a transparent composite film, it is also recommended that the cursor be printed on a white background because of the influence of the color of the article in contact with it, thereby reducing the interference with other background colors.
For some multi-row packaging machines, as long as there is a group of electric eyes, this group of electric eyes is generally placed in the middle of the composite membrane coil. After being packaged, it can be left in the finished package, or it can be removed as a margin. If left in the finished product, there will be such a problem: in the same batch of products, there are cursors and cursors. In order to avoid this difference, a cursor may be printed on each column of packaging materials in a multi-row packaging machine (although The packaging machine only needs one column cursor.)
Second, the design of printing technology
A lot of art experts engaged in the design of manuscripts only designed from the point of view of art or from the point of view of lithographic printing processes, and did not fully consider the particularities of intaglio printing technology. From the perspective of gravure printing technology, the following aspects should be noted in the design of composite flexible packaging manuscripts:
1. Gravure printing overprint accuracy can only reach 0.2mm, so the stroke is less than 0.4mm text and graphics (especially text), can not use multicolor overlay to print, can only be printed with a single ink, otherwise it is easy to cause ghosting phenomenon.
2. Small texts and patterns should be printed with hollow cutouts. It is not advisable to use multi-colored overlays for hollow prints. It is also not possible to print photos directly with the background color of the photos. It is also not appropriate to use fine-grained patterns to overprint text patterns for small texts and designs.
3. Pay attention to the size of the text and the thickness of the strokes. Too small texts and too fine strokes may not be printed, and often there are printing faults that break pens or even lack pens. If the text is too small, if the strokes are too dense and the lines are too thick or the printing plate is too dark, it is easy to have a phenomenon of “pasteâ€.
4. The transfer performance of gravure printing is inferior to lithographic printing. There is a problem of blocking printing. In general, it should try to avoid using less than 10% of outlets. In particular, the background color of a large area should be avoided too shallow network points, otherwise the reproduction of its network points is not good, easily causing uneven color, easy to change color. Even if it is printed at the beginning, it is too shallow to be easily affected by the wear of the printing roller in the printing process, which affects the hue and the printing plate number is low. Large area light colors are recommended for spot color printing.
5. Although in principle, all colors can be produced with the superposition of three primary colors, in fact, there are many colors with high color purity, very bright colors, and some special colors such as fluorescent color, transparent color, gold color, and silver color. Color can be printed out, and at this time it is also necessary to make a spot color roller for printing.
6. Some special inks such as pearlescent inks, due to the coarser ink particles, should be deeper. Some inks such as fluorescent colors and some deeper transparent colors, due to poor color rendering of the ink, must reach deeper in order to achieve deeper colors. Due to the coarse particles and other reasons, general pearlescent ink, gold ink and silver ink should not be used to hang light net printing.
7. Special care should be taken not to try to place patterns and lines too densely at a certain position in the longitudinal direction. Otherwise, this position will produce violent tendons at the time of printing and the pressure will be large, causing ink stickiness. At this time, it may be appropriate to reduce the number of lines. The thickness of the ink layer.
8. Expand the problem. When a text pattern is completely nested with another text pattern, the light text pattern should be expanded to an appropriate size (usually 0.2-0.4mm) to overlap with the darker text pattern, otherwise it is very Easy to expose the background at the junction. As to the extent of lightness, it is related to the color. If the two colors are in color, the overlapped part will produce black lines, which will affect the appearance and should be minimized.
9. The problem of color order is generally printed from dark to light colors, and the color of the table printing is generally dark in color after printing. The two do not look the same. Actually, from the naked eye, one sees that the order is exactly the same, that is, the dark one is seen first. For color printing with photographs, the three primary colors should be printed consecutively. Do not place any special color in them. This is not conducive to overprinting of the three primary colors and fusion of the layers of ink. The printed photos will be less effective.
10. The thickness of the hanging net is divided, and at the same percentage, the coarse net net point is easy to reproduce. However, if the dot of the text pattern is thick, the lines of the strokes will not be smooth and affect the appearance. Pay attention to some colors (such as dark green) in the design of the hanging net, it is difficult to get a smooth and bright printing effect within a certain percentage of the hanging net, tears or water ripples will appear.