Precautions for label printing with the most effic

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Precautions for label printing with unit flexographic printing machine

selection of color sequence

at present, the graphic part of labels printed with flexographic printing is mainly field, line, text, etc., and most of the printing materials used are paper, aluminum foil, plastic film, non drying glue, etc. When printing absorbent printing materials with water-soluble or solvent based inks, the materials will swell after drying with infrared hot air, which will affect the overprint accuracy. Therefore, we should be careful when considering the printing color sequence to avoid such problems. The color plate containing a large area of field should be printed in the back unit as far as possible, because the substrate absorbs a lot of ink and then passes through infrared drying, the pumping change of the field unit is naturally larger than that of other units, and has a great impact on the overprint process. If such units are printed after words and lines, it will more or less have a positive impact on the overprint. If the field part must be printed in the front color deck, the compensation in the up and down direction can be consciously increased slightly to make up for the loss caused by the pumping of printing materials and make the overprint more accurate

precautions for plate making

1. trapping

when making flexo, a certain amount of trapping is conducive to printing registration, provided that the trapping size is appropriate. Trapping is set too small or no trapping treatment will cause poor registration (white leakage) in printing; If trapping is set too large, a large outline will appear on the edge of the print, which will affect the visual effect and the overall effect of the label

2. layout design

because flexo printing basically uses web paper for printing, especially the application of seamless sleeve technology, which greatly saves paper, but some flexo printing machines can't realize online die cutting, and they still need to go through subsequent processing (cutting, etc.) to produce finished products. Therefore, when designing the layout, we should fully consider leaving sufficient margin for subsequent processing, The paper saving rate should not be considered unilaterally and the qualification rate of subsequent processing should not be ignored

the choice of raw and auxiliary materials

when printing labels with flexo, the choice of raw and auxiliary materials will directly affect the quality of printed products. Therefore, the choice of raw and auxiliary materials should not be limited to the unit price, but should take the quality of printed products as the first element, and summarize and analyze the comprehensive cost of products, so as to make a choice. The main raw and auxiliary materials that need to be considered are paper and ink

1. Paper

generally speaking, the label pattern is mainly on the ground, which puts forward certain requirements for the smoothness, whiteness and gloss of the paper. If you want to obtain a satisfactory label field printing effect, the smoothness of the paper must be high in order to ensure that the printed matter has a uniform density value and that the surface of the printed matter will not be scratched. Because the paper with high gloss and whiteness can enhance the contrast between ink and paper, make the graphics and texts clearer, and make the bright effect of flexographic ink more intense, therefore, when choosing flexographic label paper, gloss and whiteness are particularly important. Compared with the above two indicators, the opacity of paper has a greater impact on the quality of flexographic labels. Therefore, the whiteness and gloss of paper should be selected under the condition that the opacity of paper is consistent. Generally, the whiteness should be higher than 85% and the gloss should be higher than 55%

in addition, since flexo printing is generally printed on web paper, the tensile strength of paper is an important selection index. Only if the tensile strength is good, can the paper maintain stability and continuity in the whole printing process, and make the label maintain good overprint accuracy. In addition, the surface strength of the paper is also an important selection index. The seams of the trim and decoration lines are also dirt resistant. Only if the paper has good surface strength, can the field printing be full, and there will be no printing surface blooming and uneven color

2. ink

due to the bright colors to be given to the label, the proportion of pigments in the ink will be increased to a certain extent, but this will have a certain impact on printing. If the proportion of pigment is too high (higher than 35%), the viscosity of the ink will increase, and the thixotropy of the ink will increase, which will affect the transmission of the ink in the printing process. At this time, it is necessary to stir the ink and store the ink at a suitable temperature (20 ℃) as far as possible

when selecting ink, we should also consider the particle size of ink and the drying performance of ink. Especially when there are not only large areas of color blocks, but also words, lines or eye tone images on the label, it is more important to consider that different patterns have different requirements for the drying speed of the ink, so as to make the prints clean and tidy (there is no paste and galling). In addition, too thick pigments will cause certain wear on the wrinkle roller, which should also be paid attention to when selecting ink

in a word, we should strive to save raw and auxiliary materials, but we should not only consider the price factor. The main thing is to compare the quality and accuracy of the product. We should consider it from the perspective of comprehensive cost, and conduct a comprehensive evaluation according to the product qualification rate and man hour consumption rate, so as to select the appropriate printing materials

requirements of printing environment

when applying flexographic printing labels, environmental factors are very important. We know that the graphic part of the label not only has a large area of the field, but also has words, lines and eye tone images. Due to the limitations of these conditions, it will have a certain impact on the drying of the ink. The drying speed of the ink in the printed words, lines and other parts will be accelerated due to the volatilization of ammonia and amines. At this time, it is necessary to improve the microenvironment of the ink and install a humidifying device at the ink tank to inhibit the volatilization of such substances, So as to control the drying speed

in addition to controlling the micro ring, the control of the overall environment in the printing process is also very important. Flexo printing is highly sensitive to the environment. When printing labels with different types of paper and different patterns (mainly on the ground or lines), the choice of humidity is different. Generally, the humidity of waterproof paper printing needs to be higher. When printing a large area of the field, the humidity should be lower. Too high ambient temperature will affect the drying effect of inks (water-based inks, solvent based inks) and cause printing products to appear paste and other phenomena; If the temperature is too low, the viscosity of almost all kinds of inks will increase, which will reduce the fluidity of inks and bring inconvenience to printing. Therefore, it is necessary to stabilize the temperature and humidity of the printing environment within a certain range

in China, the northern region has obvious changes in four seasons, with large differences in temperature and humidity. The climate is mainly dry. It is best to close the printing environment and install humidifiers, air conditioners and other equipment to create an environment suitable for flexo printing; The climate in the south is unique for flexo printing, but due to the rainy weather in the south, workshop dehumidification should be a key to create a flexo printing environment. The ambient temperature and humidity range suitable for flexo printing is generally: the temperature is about 25 ℃ and the humidity is 50% - 60%

the quality of operators

in label flexo printing, human factors are also easy to be confused if you do not use expertise. Operators should mainly have the following qualities

1. High heart. The heart comes first. It's useless to talk about anything without the heart

2. Have a certain understanding of mechanical principle and electrical knowledge. When operating the flexographic press, we can fully consider the mechanical and electrical characteristics of the press, avoid unnecessary waste in printing, and eliminate some problems existing in the press

3, have a certain foundation of chemical knowledge. When adjusting the ink, it can be considered from the physical and chemical point of view, so that the ink can achieve the best use effect

4. Master various printing processes. Only by mastering various printing processes can we timely feed back some problems in the design, so that the label design is suitable for flexographic printing as much as possible, so as to save raw and auxiliary materials and avoid waste.

5. Be good at summarizing. Only by summarizing and refining the problems in printing in time can we continuously improve our ability

at present, flexographic printing is being favored by packaging and printing manufacturers because of its environmental protection, bright colors, stability and other characteristics, and its proportion in label printing is also increasing. Therefore, how to give full play to its characteristics is also becoming a topic for flexographic workers. It is believed that flexographic printing will play a more important role in label printing on the premise that the country vigorously advocates environmental protection. (end)

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