Experience of the hottest corrugated box dot print

2022-08-16
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With the prosperity of commodity economy, market competition is becoming increasingly fierce, prompting commodity manufacturers to strive to improve the quality of outer packaging, beautifying packaging has become an effective means of commodity publicity and promotion. The quality of corrugated box packaging and printing has been paid more and more attention by commodity manufacturers and consumers. In order to enhance the competitiveness of products and improve the packaging grade of products, many corrugated box layouts began to use point graphics to highlight products and enrich the layout

in packaging design, the graphics have strong expressiveness and visual impact, which is easy to attract people's attention. The graphics printed with dots are difficult to counterfeit, have good anti-counterfeiting performance, and have a sense of hierarchy and three-dimensional, which is pleasing to the eye. To get high-quality point effect, we must first work hard on the design draft. Dot is the basic unit to realize that prints can reflect the changes of layout levels, the intensity of color gradients, and the natural division. It plays a role in determining the color of prints, and takes carbon fiber or carbon fiber fabric as the reinforcement level and image contour in printing. The intensity of printed graphics is expressed by the size of points. The larger the number of points, the thicker the printing ink of graphics, and vice versa. For corrugated box printing, too dense dots are easy to cause paste phenomenon; If the dots are too thin, the graphic details will be lost and the graphic effect will be affected. We must grasp the accuracy when making. Graphics are divided into vector graphics and bitmap, and their point processing methods are different

point processing method of vector image

for vector image, it is necessary to control the gray level, and reflect the graphic level through the change of gray level. The size of gray determines the size and thickness of points. When outputting the film used for printing, the number of lines output also determines the number of graphics points. The larger the number of lines, the more points. When outputting, you must choose the appropriate number of lines. Only when the gray-scale figure of vector image and the number of output lines are considered comprehensively, can a satisfactory point effect be obtained

bitmap image point processing method

1. The most basic processing method of bitmap image

photoshop is the image processing software widely used at present. For bitmap, after scanning the image, the most basic processing method is to remove the points first, and execute filter → noise → speckle in Photoshop, The function is more and more powerful. Sharpen the 3D printing technology of filter → shaper → unsha, that is, SLA), print and form RP mask, then adjust the overall contrast of the image, and execute image → adjust → levels. The usual way is to pull the triangle on the left towards the middle

2. Create and select the required point image

after processing the scanned image, select Show paths from windows, use the pen tool to draw the path of the point image part to be made, keep the path (save path) and name (name), then cut the defined path (clipping path), and save the image as (save as) Photoshop EPS format, which can be displayed in drawing software such as freehand Place the required image part in pagemake

3. Bitmap point formation

first convert the processed image to grayscale mode, execute image → mode → grayscale  and then convert to bitmap mode. Enter the bitmap dialog box, where the output data in resolution is generally consistent with the input data, Then select halfone screen from the mothod (method) and enter the halfone screen dialog box after confirmation. According to the needs of customers, you can select six point effects of round, diamond, ellipse, line, square and cross  try to choose the circular point with the shortest edge perimeter and the largest connotation capacity to reduce the dot expansion rate in printing. The selected point arrangement angle (angle) must avoid the line arrangement angle of the ink transfer roller. The size and thickness of the points are adjusted by the parameters in frequency, so as to obtain the point pattern suitable for the printing conditions. The formed point graph can be printed out in advance according to the ratio of 1:1 to view the point effect, so as to adjust or deliver it to the customer for approval

production of dot printing resin plate

plate making can be carried out after the design draft is output into film. The photosensitive resin plate used to make dot graphics requires high hardness, preferably 45 ~ 50 ° Shore A, and the material has low elasticity and slow denaturation recovery, which can ensure the reproducibility of dot graphics

the dot resin plate on the package of the same product should be made at the same time as much as possible. It is very easy to have dot printing depth differences and produce different effects. If the photosensitive resin plate of dot pattern cannot be processed at one time, the time of back exposure, main exposure, washing, drying, debonding and post-processing must be strictly controlled during plate making, and records must be made to keep the data processed each time consistent, so as to obtain the photosensitive resin plate of dot pattern with the same effect

correctly select the corrugation roller

when designing point graphics, we should also consider the corrugation roller of enterprise printing machine. Corrugated roller is the "heart" of corrugated box printing machine. Carton manufacturing enterprises are constantly improving the grade of corrugated roller in line with the market requirements for the improvement of corrugated box printing fineness. At present, metal ink transfer roller is widely used in corrugated box printing machine, and its accuracy is mainly guaranteed by the manufacturing process and extrusion technology of corrugated cutter and roller. In the process of graphic point printing, the number of lines, the shape of lines and the arrangement angle of the metal ink transfer roller should be mainly considered:

the number of lines of lines

the lines of the metal ink transfer roller are composed of holes and walls. In order to obtain sufficient ink storage, on the premise of ensuring the accuracy of the tool, the holes must reach the best depth during processing, and the wall is always required to be as narrow as possible to ensure the largest possible volume. The line selection of metal ink transfer roller mainly depends on the actual ink demand of corrugated box printing. In corrugated box printing, generally between 150 ~ 300 lines/inch, 165 lines/inch can be selected for large-area field printing, and 180 ~ 300 lines/inch should be used for graphic point printing. The selection of the number of lines of the printing resin plate has an important relationship with the number of lines of the embossing roller. The ratio of the number of lines of the printing resin plate to the number of lines of the embossing roller should be 1:3.5 ~ 4, so as to ensure that the minimum point of the highlight area in the printing resin plate will not fall into the hole of the embossing roller and produce ink spots, which will affect the printing quality

the shape and arrangement angle of the grain

different grain shapes on the metal grain ink transfer roller determine different volumes and ink storage and delivery volume. Most of the shapes of the grain are square pyramid, hexagonal, pyramid, hexagonal connected, diamond, etc. With the same number of lines, the shape of the pattern is different, and the volume is also different. With the same number of lines, choosing the appropriate pattern shape can obtain a better printing effect

the line arrangement angle of the metallic ink transfer roller refers to the included angle with the axis of the roller. Generally, the square pyramid shape and pyramid shape are 45 °, while the hexagonal shape, hexagonal connected shape and diamond shape are 60 °, and there are also 30 °. If the line angle of the printing resin plate coincides with that of the embossing roller, or the line number of the printing resin plate does not match the line number of the embossing roller, or the point shape of the printing resin plate coincides with that of the embossing roller, moire will be produced in printing, which must be avoided in the design and production of point graphics. Control the quality of water-based ink

in order to obtain high-quality dot printing effect, we must master the pH value, color concentration, hue, drying performance and flow performance of water-based ink

the pH value of water-based ink should be controlled at 8.5-9. Due to the large area of the corrugated box, the plate roller contacts more air, and the printing speed is slow, the water-based ink should be selected with a slower drying speed, otherwise the ink is easy to dry and fix on the printing plate, making the field printing inaccurate, and the printing plate paste. When the ink dries and is not easy to wipe off with water after parking, it is necessary to replace the water-based ink in this case. When printing the laminated ink, the requirements for the fluidity of the ink are relatively strict. It should be noted that the fluidity of the latter color is slower than that of the previous color ink, otherwise the laminated ink will not print well. Ink contains enzymes and amines, which are easy to volatilize, so that the ink thickens, and it is easy to paste the starting point printing plate. Strengthen the control of graphic dot printing process. Generally, try to avoid dot graphics and large-area ink blocks printing together. Dot graphics and large-area ink blocks require different ink volume and pressure when printing. It is often difficult to master them when printing together. If large-area ink blocks are taken into account, dot enlargement or paste will occur; If you take care of the dot graphics, large-area ink blocks will appear under insufficient pressure, resulting in false and white field printing. If large areas of ink blocks and dot graphics are printed separately, pressure adjustment and color control are much simpler

however, at present, most corrugated box printing layouts either have gradient points, large areas of lines, small parts of ink blocks, or large areas of ink blocks, small parts of lines. It is difficult to print the two separately. In this case, the thickness of the field part can be padded up by 0.15-0.30mm to improve the plate pressing and printing pressure. If it is a gradient point, when pasting on the field part, pay attention to the transition between the field and the line, and the paper should be cut into sawtooth shape to avoid hard mouth

effective control point expansion phenomenon

in the process of printing, a certain degree of point expansion must exist, and the important thing is how to control it. This requires the printer to adjust the pressure as lightly as possible to obtain the smallest point expansion, and this will also provide endless development power for the extruder industry. Make a detailed record of the parameters of brush adjustment, so that the same printing effect can be tracked in the future

master the printing pressure

appropriate printing pressure is very important to the printing quality. Corrugated box flexographic printing belongs to light pressure printing, and the contact pressure between rollers must be adjusted in strict accordance with the requirements to ensure uniform line pressure. If the pressure is too high, it will cause abnormal wear and tear of the roller, mechanical fatigue, deformation, and even journal fracture. It will also damage the printing plate, expand the printing point, blur the printing, and affect the printing quality of corrugated boxes

ensure the normal running speed of the printing machine

the running speed has a certain relationship with the ink transfer volume. The running speed is slow, the ink transfer volume is large, the running speed is fast, the ink transfer volume is small, and the stable running speed can obtain a stable ink transfer volume. Because the viscosity of water-based ink is in direct proportion to the ink transfer volume, a slower running speed, a higher viscosity of water-based ink and a low number of lines can be used for large-area field printing. Dot printing requires faster running speed, low concentration of water-based ink and higher number of lines

strictly clean the wrinkle roll and dot printing plate

the biggest feature of water-based ink is that it is extremely difficult to clean after drying, so the cleaning work is particularly important. During temporary shutdown, the metal ink transfer roller should be separated from the printing plate roller, but the ink transfer roller should continue to contact and rotate with the rubber ink scraper roller to prevent the ink from drying up and depositing at the bottom. When the metallic ink transfer roller is finished and shut down for a long time, the ink transfer system must be thoroughly cleaned and wiped with a clean cloth, rather than being flushed with water. If it is indeed accidentally blocked, it is necessary to use regular cleaning agents or even cleaning machines for large-scale cleaning, but this is a last resort. The cost of large-scale cleaning is very high, and it may not be successful every time. If you don't pay attention to the maintenance of the wrinkle roll, wait until it is blocked, and then think of a way, which is more expensive

after printing, the dot printing resin plate should be cleaned immediately to prevent ink from printing on the plate

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