How to ensure the printing effect of high screen f

2022-08-08
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How to ensure the printing effect of high-speed flexo carton

flexible ink of high-speed corrugated paper "> printing is a coordination process of an integrated system, which requires the adjustment and mutual coordination of all relevant links to achieve a relatively optimal value. Such as plate making, ink painting, corrugated paper and paperboard, printing equipment, printing technology and other links are very important, and they should be well coordinated. How to realize the flexible printing of high-speed corrugated paper? The key technologies are:

first, in terms of flexible plate making, determine the best one that can not only be suitable for printing, but also reflect the product Solution of design effect

1 Determine the printing suitability conditions

first of all, understand the printing equipment. For example, the color number of the unit, the type and number of lines of the corrugated roller, the basic situation of the paper feeding system and the scraper system. There are also paper types, such as whiteboard or coated paper. If possible, a set of test plates for testing the printing suitability of the printer can be provided. It includes a ladder bar for testing the expansion of different line points of the flexo, a color block for measuring the field density value of the ink, a simple chromatography for overprinting different point proportions, yin-yang characters and straight lines of different font sizes, a module for measuring the chromatic error, a pressure bar for observing the printing balance pressure, and so on. The test printing plate is required to be completed under normal production conditions such as normal printing board, standard production water-based ink, normal printing pressure and speed. Of course, some printing conditions can be changed to get different test samples. Through the analysis of the test samples, we can get the printing suitability of this type of printer under normal conditions. The point expansion, curve, field density, hue value, point collision, influence of color sequence, reduction of fine lines, overprint error and printing balance pressure of each color can be obtained

combined with the test data obtained above and the printing effect of the test sample, a set of color matching management system for this printer can be established, such as establishing point compensation curve for point expansion, correcting screen color and gannina curve, color simulation and matching of proofing, etc

2. Determining the plate making process and color separation scheme

these situations bring a lot of sales to the environmental experimental equipment industry. In external flexo plate making, the determination of color separation process scheme is a key factor, which plays a decisive role in the success of high-speed wire products printing to some extent. The color separation of flexible printing should use as few colors as possible and use as pure colors as possible to complete the superposition of colors, which is very helpful to printing and reduce costs

3. Selection of the number of lines and angles of the printing plate

the number of lines of the printing plate is restricted by the number of lines of the ink transfer roller, and the ratio between the two is required to be more than 1:5. The 400L/in corrugation roller can achieve a maximum of 80L/in printing plate. If the number of lines is too high, it is easy to paste the plate and produce moire. Therefore, the higher the number of lines, the better. Moreover, the printing effect of 80L/in and 75L/in will not be much different in terms of fineness

the addition angle of flexo printing mainly adopts two angles: 7, 37, 67, 82, and 7, 22, 52, 82 according to the angle of the corrugated roller. However, we should start from the actual situation of the product, not one size fits all. For example, for monochrome hanging linear patterns, the hanging angle must be 45 degrees or 0 degrees, otherwise there will be obvious jagged edges on the hanging patterns. The selection of overlapping pattern angle should be based on the principle that the hue angle of the main tone of the product pattern is 30 degrees different. If the skin of the portrait is mainly yellow, the value of the color difference material between magenta and yellow should be more than 30 degrees; If the landscape is dominated by green tones, the color difference between cyan and yellow should be more than 30 degrees, otherwise moire will easily occur. Before plate making, conduct proofing simulation to determine the best addition method. Discrete points adopt certain additive technology, which increases the anti-counterfeiting of products

4. At present, the direct plate making system mainly adopts extremely high transfer technology, which can directly image on the resin plate after color separation and assembly. Digital printing plate has the advantages of complete dot type, extremely high light spot is not easy to lose, low printing dot expansion rate, step length, Dafang daining introduction point, non paste and so on. It is the best choice for flexo high-speed plate making

II. Requirements of high-speed flexible printing on plates, paper, paperboard, water-based ink and equipment

1 Plate material selection for high-speed wire plate making: the plate used for high-speed wire printing has a hardness slightly higher than that required for general printing. This is because this printing process requires a small amount of ink to accurately reflect the fine dots. Too soft printing plate will lead to excessive ink transfer, which is not conducive to ink control, and is prone to color deviation, blocking and other faults. In addition, it is also required that the plate should have a good point reproduction range and be able to make small highlights; It has uniform thickness and good flatness, which is convenient for Huaibei City to set up Anhui ceramic aluminum New Material Research Institute of Shanghai Jiaotong University for light press printing and easy reproduction of the original; It has good elasticity, can return to the original thickness after being pressed, and the plate should have a certain toughness, and small points are not easy to wear. At present, the plates commonly used in this kind of printing include DuPont TDR, etc

2. Paperboard: to achieve the effect comparable to offset printing, it is best to choose Coated Whiteboard. Because the Coated Whiteboard has a better finish, the imprint is more shiny and bright. The surface gloss of ordinary whiteboard is poor, and the imprinted color is dim. In addition, coated whiteboard is different from offset paper and coated paper. It retains some of the original characteristics of whiteboard, permeability and adhesion, which is conducive to the printing of water-based ink. Paperboard can be selected with uniform thickness, flat paper surface, moisture controlled at 9+2% and good hardness. E-type, F-type or G-type corrugated, with 180g/m2 facial paper. This kind of paperboard has low corrugation and flat paperboard, which can withstand greater pressure, reduce ribs lines, false impressions and other phenomena, and improve the quality of prints

3. Ink: ink is a key factor in the whole printing process. Water soluble acrylic acid is compounded with acrylic lotion, and high coupling agent is added. For high-performance parts with four-color overprint, we must pay attention to the choice of ink. The ink of printing coated paper is different from ordinary ink. It mainly requires the following characteristics: good fineness, clear dots, delicate patterns; High gloss, bright color and luster; Low viscosity, no blocking, ink bar, clean and refreshing graphics and texts; High color content, full color and rich connotation; Good adhesion, anti-wear, no fading; Good leveling, uniform color, no bottom exposure; Fast drying, good color folding effect, no dragging; Good overprint, good compatibility between colors, natural and harmonious colors, rich layers

4. Equipment requirements: (1) scraper: the printing machine that can complete high-speed printing must have a scraper. It also requires sealed double scraper and maintains the effectiveness of the scraper, so as to accurately control the ink transfer; (2) Closed circulating ink path: the closed ink path is conducive to preventing the ink from excessive contact with the air, preventing some components of the ink from volatilizing, oxidizing, dissolving into bubbles, etc., and maintaining the stability of the ink components can successfully complete high-quality printing; (3) High line ink transfer roller: This is one of the most important conditions for high-line printing. The higher the number of lines, the higher the line that can be printed, and the smaller the ink transfer volume, which helps to reproduce small highlights; (4) Suction paper feeding and whole process adsorption paper feeding: it can improve the flatness of paperboard, smooth paper feeding, ensure accuracy and register accuracy; (5) Liner (between the printing plate and the plate roller): a better liner can buffer and adjust the pressure, protect the fine spots, and improve the service life of the printing plate

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