Corrugated carton outlet printing experience

With the prosperity of the commodity economy and increasingly fierce market competition, commodity manufacturers are trying to improve the quality of outer packaging, and beautifying packaging has become an effective means for product promotion and promotion. The quality of corrugated carton packaging and printing has been increasingly valued by commodity manufacturers and consumers. To enhance the competitiveness of products and improve the packaging quality of products, many corrugated carton layouts have begun to use dot-dot patterns to highlight products and enrich the layout.
In terms of packaging design, the expressiveness and visual impact of the graphics are relatively strong and can easily attract people's attention. The use of dot-printed graphics is difficult to counterfeit, and the anti-counterfeiting performance is good, with rich sense of hierarchy and three-dimensionality, making people pleasing. To get a high-quality dot effect, first work hard on the design draft. Dots are the basic units that enable printed products to reflect changes in the level of the publishing surface, shades of color, and demarcation in nature, and play a role in determining the colors, levels, and contours of the printed product in printing. The degree of shade of printed graphics is expressed by the size of the dot. The larger the dot number, the thicker the graphic printing ink, and vice versa. For corrugated box printing, the dense dot network can easily cause stencil printing; if the dot network is too thin, the graphics details will be lost, affecting the graphics effect, and the production must be accurate. The graphics are divided into vector and bitmaps, and their dot processing methods are different. Vector Dot Processing Methods For vector graphics, it is necessary to control the gray level, and the gray level changes to reflect the level of the image. The size of the gray scale determines the dot size and the thinness. When the vector graphic is used to output film sheets for printing, the number of output screen lines also determines the number of graphic network points. The larger the number of network lines, the greater the number of network points, and the number of screen lines must be selected when outputting. Only the combination of the vector graphics grayscale and the output line number can be satisfied with the dot effect.
Bitmap image dot processing method The most basic method of bitmap image processing PhotoShop is currently widely used in image processing software for bitmaps. After the image is scanned, the most basic processing method is to first remove the dots and perform Filter→Noise→Despeckle in PhotoShop. Color), and then sharpen the Filter → Shaper → unsharp mask  sharpening , and then adjust the overall contrast of the image, perform Image → Adjust → levels, the usual practice is to pull the left triangle to the middle.
2. After selecting the required dot image and processing the scanned image, select show paths from windows, use the pen tool to draw the path to the dot image part to be created, save the path and name, and then cut. Clipping path, save the image as Photoshop EPS format, you can use graphics software such as Freehand, Pagemake to use the desired image part.
3. Bitmap meshes are formed by first converting the processed image to grayscale, performing Image → mode → Grayscale, then converting to bitmap mode, entering the bitmap dialog box. The output (output line number) data in the resolution is generally the same as the input (input line number) data, and then select the halfone screen from the mothod (method). After confirming, enter the halftone screen dialog box. Depending on the customer's needs, you can select Round, Diamond, Ellipse, Line, Square, Cross, and try to use the shortest perimeter possible. Concentration of the largest circular outlets in order to reduce the dot gain rate in printing. The selected mesh arrangement angle (angle) must avoid the arrangement angle of the anilox roller, and the size of the mesh dot is adjusted by the parameter in Frequency to obtain a dot pattern suitable for printing conditions. The dot pattern formed can be printed out in advance at a ratio of 1:1 to view the dot effect for adjustment or delivery.
The production design of the dot-printed resin plate can be plated after being output as a film. The photosensitive resin plate used to fabricate the dot pattern requires a high hardness, and 45-50o Shore A is suitable, and the material is low in elasticity and denatured. Slower than can ensure the reproducibility of the dot pattern.
The production of resin dots on the packaging of the same product should be carried out as much as possible at the same time. Once in a batch, it is extremely prone to discrepancy in dot printing, resulting in different effects. If the photoresist pattern of the dot pattern cannot be processed once, the back exposure, main exposure, rinsing, drying, de-sticking and post-processing time must be strictly controlled during the plate making, and records should be made so that each processing data is consistent to obtain The same effect dot pattern photosensitive resin plate.
When choosing the anilox roller dot pattern design correctly, consider the anilox roller of the enterprise printing machine. Anilox roller is the “heart” of corrugated box printers. Carton manufacturers are constantly improving the quality of corrugated cartons in accordance with the requirements of the market. They are continuously improving the quality of anilox rollers.
The current widespread use of corrugated box printers is metal anilox roller, whose accuracy is mainly ensured by the manufacturing process and extrusion technology of the reticulated cutters and rollers. In the graphic dot printing, the number of reticulated lines, reticulate shapes, and arrangement angles of the metal anilox roller should be taken into consideration: The number of reticulate lines The reticulation of the metal anilox roller is composed of a network of dots and a network wall. Composition, in order to obtain a sufficient amount of ink storage, under the premise of ensuring the accuracy of the tool, the mesh must be at the best depth when processing, the net wall is always required to do the narrower the better, in order to ensure to obtain the largest possible volume . The metal mesh roller selection depends on the actual ink demand of corrugated box printing. In corrugated box printing, it is generally between 150 and 300 lines/inch. A large area of ​​field printing can use 165 lines/inch. Network lines, graphics dot printing should use 180 ~ 300 lines / inch anilox roller. The number of lines for the printing resin plate has an important relationship with the number of lines of the anilox roller. The ratio of the number of printing resin lines to the number of lines of the anilox roller should be 1:3.5 to 4, so as to ensure the high light area in the printing resin plate. The minimum dot will not sink into the anilox roller's cell and create dots, which will affect the print quality. Reticulate shape and arrangement angle The different reticulate shapes on the metal anilox roller determine the different volumes and the amount of stored ink. The shape of the reticulation is mostly quadrangular prismatic, hexagonal, pyramidal, and hexagonal. Diamond and so on. The same number of lines, the shape of the reticulate, the volume is also different. With the same number of lines, choose the right mesh shape to get a more ideal printing effect.
The arrangement angle of the metal mesh roller roller is the angle between the roller axis and the roller axis. In the general case, the quadrangular prismatic shape and pyramidal shape are 45°, while the hexagonal, hexagonal connected shape, and diamond shape are 60° and 30°. If the printing resin plate and the anilox roller coincide in the angle of the screen or the ratio of the number of lines of the printing resin plate and the number of lines of the anilox roller does not match or the dot shape of the printing resin plate matches the network pattern of the anilox roller, the printing will generate a moiré pattern. , must be avoided when designing the dot pattern. The quality of a good water-based ink requires high-quality dot-matrix printing. The pH, color density, hue, drying performance, and flow properties of the water-based ink must be well understood.
Water-based ink PH value should be controlled at 8.5-9. Due to the large area of ​​corrugated cartons, the roller contact with air, and the slow printing speed, the water-based ink must be selected to be slower in drying speed. Otherwise, the ink can easily be dried on the printing plate, making the actual printing on the ground inaccurate. Version. When a parking ink is dry and cannot be easily boiled off with water, the water-based ink needs to be exchanged when this happens. When printing the multi-colored ink, the fluidity of the ink is required to be strict, and it should be noted that the latter color is slower than that of the previous color ink, otherwise the multi-colored ink printing is not good. Ink and ink containing yeast, amine, easy to volatilize, so that the ink thickens, easy to cause dot printing plate paste to strengthen the graphics dot printing process control Under normal circumstances, as much as possible to avoid dot pattern and a large area of ​​ink printing together. Dot pattern and large-area ink sticks require different ink volumes and pressures when printing. When printing together, they are often not easy to grasp. If you take care of large-area ink sticks, you will create dots or pastes; take care of the dot patterns. A large area of ​​ink sticks will appear to be under pressure, resulting in the actual printing is not true and white. If large areas of ink and dot pattern are printed separately, pressure adjustment and color control are much simpler.
However, at present, most corrugated cartons have either gradient meshes or large-area network cables or small pieces of ink, or they have a large area of ​​ink blocks and a small part of network cables. It is difficult to separate the two. In this case, the thickness of the solid part can be increased by 0.15-0.30mm to improve the plate press and press. If it is a gradient mesh, when the sticker on the field is partially displayed, it should be noted that at the transition between the field and the network cable, the paper must be cut into a zigzag shape so as to avoid a hard mouth.
Effectively controlling network expansion During the printing process, a certain degree of dot gain must exist. The important thing is how to control it. This requires the printer to adjust the pressure as light as possible to obtain the minimum dot gain and to print. The parameters of the machine adjustment are recorded in detail so that the same printing effect can be followed in the future. Grasp the printing pressure The appropriate printing pressure is crucial to the printing quality. The corrugated carton flexo printing belongs to light pressure printing. The contact pressure between the rollers must be strictly adjusted according to the requirements to ensure uniform line pressure. If the pressure is too high, it will cause abnormal wear of the roller, mechanical fatigue, deformation, and even the fracture of the journal, as well as damage to the printing plate, the phenomenon of printing dots, printing fuzzy, and so on, affecting the printing quality of corrugated boxes.
To ensure the normal operation speed of the printing press, the operation speed has a certain relationship with the ink transfer amount, the operation speed is slow, the ink transfer amount is large, the operation speed is fast, the ink transfer amount is small, and the stable operation speed can obtain a stable ink transfer amount. Because the viscosity of the water-based ink has a certain proportional relationship with the amount of ink transferred, large-area field printing can use slightly slower running speed and slightly higher viscosity of water-based ink and a low number of lines. The dot printing requires a faster operating speed and a lower concentration of water-based ink and a higher number of lines.
Strictly do a good job in the cleaning of the anilox roller and dot printing plate. The biggest feature of the water-based ink is that it is extremely difficult to clean after the dry-knot, and the cleaning work is particularly important. In the temporary shutdown, the metal anilox roller should be separated from the plate roller, but the anilox roller should keep in contact with the rubber squeegee roller to prevent the ink from depositing on the bottom of the screen. When the metal anilox roller is shut down and stopped for a long time, the ink transfer system must be thoroughly cleaned and wiped clean with a net cloth instead of just flushing with water. If you do not plug it, use regular cleaning agents or even a washing machine to wash it. However, this is a last resort. The cost of large washing is high, and it may not always be successful. If you do not pay attention to the maintenance of anilox roller, it will be more costly to think about it after it is blocked.
After the printing is completed, the dot printing resin plate must be immediately cleaned to prevent the ink from drying on the plate, causing the dots to clog, resulting in a bad plate. (Li Yutian)

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