Functional High Dot Flexo Overlay Carton Technology Solution

The flexible printing of high-line corrugated paper is an integrated system that requires adjustment and mutual cooperation of all relevant links to achieve a relatively optimal value. Such as plate making, ink painting, corrugated paper and cardboard, printing equipment, printing technology and other links are all very important and must be well coordinated. How to realize the flexible printing of high-line corrugated paper? The key technologies are:

(a) In the field of flexible platemaking, determine the best solution that can be suitable for printing, but also reflect the product design effect

1. Determine printability conditions

The first thing to know about printing equipment. Such as the unit color number, the type and number of anilox rollers, the paper feeding system, and the basic conditions of the squeegee system. There are paper types, white paper or coated paper. A conditional test plate can be provided to test the printability of the printer. It includes a ladder strip for testing the expansion of different flexographic screen points, a color patch for measuring the density of ink in the field, a simple chromatogram for the overprinting of different dot proportions, a yin and yang character and straight line with different font sizes, and a module for measuring trapping errors. To observe the pressure balance of printing pressure bar and so on. Test plates are required to be completed under normal printing paperboard, standard production water-based ink, normal printing pressure, and vehicle speed. Of course, you can change some of the printing conditions to get different test samples. Through the analysis of the test sample, we can get the printability of this type of printing machine under normal conditions. The network expansion, curve, waterborne ink density, hue value, dot impact condition, color sequence influence, reduction of fine lines, overprint error, and printing balance pressure are available for each color.

Combining the test data obtained above and the test results of the control test samples, a color matching management system for this printer can be established, such as creating a dot compensation curve for screen dot enlargement, screen color correction and gannina curve correction, and color simulation of proofing. And match and so on.

2. Determine the plate making process and color separation scheme

In the flexo platemaking, the determination of the color separation process plan is a key factor. It plays a decisive role in determining the success of the high-line cable products. The color separation of the flexible printing is to complete the superposition of color with as little color as possible and as pure color as possible, which greatly contributes to the printing and reduces the cost.

3. Selection of printing plate screen lines and angles

The number of screen printing screens is limited by the number of screens of the anilox roller, and the ratio between the two is above 1:5. The 400L/in anilox roller can achieve a maximum of 80L/in plate, and the number of lines is too high to paste and produce moire. Therefore, the higher the number of screens, the better. Moreover, 80L/in and 75L/in printing effects do not have much difference in terms of fineness.

Flexographic screen angles mainly use 7, 37, 67, 82, and 7, 22, 52, 82 angles depending on the angle of the anilox roller. However, the screen angle must be based on the actual product, and it cannot be cut across the board. If the pattern is a straight line with a single color, the angle of the hanging net must be 45 degrees or 0 degrees. Otherwise, the edge of the hanging pattern will appear more jagged. The selection of the overlapping pattern angle should be based on the principle that the hue angle of the main hue of the product pattern is different by 30 degrees. If the human portrait is dominated by yellow tones, then the color difference between magenta and yellow should be above 30 degrees; if the scenery is dominated by green, then the color difference between cyan and yellow should be above 30 degrees, otherwise it will easily produce moire . Before the plate making, the proofing of screening is performed to determine the best screening method. Discrete outlets use a certain amount of screening technology to increase the security of products.

4. At present, the direct plate-making system mainly adopts extremely high transfer technology. After color separation and imposition, images are directly formed on the resin plate. Digital printing plates have the advantages of complete dot type, extremely high light spot not easy to lose, low print dot enlargement rate, long step adjustment, large dots, and no paste, and are the best choice for flexo high net line plate making.

(II) Requirements for flexible printing of high-line screens on board, paper, board, water-based ink and equipment

1. High-line plate plate selection: For high-line printing plate, the hardness is slightly higher than the printing plate required for general printing. This is because such a printing process requires a small amount of ink in order to accurately represent fine dots. If the printing plate is too soft, it will lead to excessive transfer of ink, which is unfavorable to the control of the amount of ink, and is prone to defects such as color cast, blocking of the net, and the like. In addition, it is also required that the plate material has a good dot reproduction range, can produce fine high-gloss dots; has a uniform thickness, good flatness, easy to achieve light pressure printing, easy reproduction of the original; there is a good Elasticity, can restore the original thickness after pressing, and the plate must have a certain degree of toughness, fine mesh points are not easy to wear and so on. The plates commonly used for such printing are DuPont's TDR.

2. Cardboard: It is best to use coated whiteboard to achieve the same effect as offset printing. Because the coated white paper has a better finish, the print is more glossy and bright. Ordinary white paper surface gloss is poor, the color of the imprint is dull. In addition, coated white paper is different from offset paper and coated paper, which retains part of the original characteristics of white paper - permeability and adhesion, and is conducive to the printing of water-based ink. The paperboard can be used for cardboard with uniform thickness, smooth paper surface, moisture control of 9+2%, and good hardness. E-shaped, F-shaped or G-type corrugated, with 180g/m2 face paper. Such paperboard has low corrugation and flat cardboard, which can withstand greater pressure, reduce the appearance of lines and imprints, and improve the quality of printed products.

3. Ink: Ink is a key factor in the entire printing process. Water-soluble acrylic and acrylic emulsions are formulated and added with a high-linking agent. For four-color overprinted high net jobs, we must pay attention to the choice of ink. The printing ink of printing and coating paper is different from ordinary ink. It mainly requires the following features: Fine fineness—clean dots and fine patterns; high gloss—bright colors and glossy; low viscosity—no blocking mesh and no ink bars , Picture and text clean, refreshing; High color content - full color, rich in content; good adhesion - anti-wear, do not fade; good leveling - uniform color, no exposed bottom; fast drying - stacking effect is good, without dragging Flowers; good overprinting - good compatibility between colors, natural and harmonious colors, rich levels.

4. Equipment requirements: (1) Scraper: The printing machine that can complete the high-line printing must have a scraper. It also requires a sealed double scraper and maintains the effectiveness of the scraper so that the ink can be accurately controlled; (2) Closed circulation ink Road: Sealing the ink path will help prevent excessive contact between ink and air, prevent certain components of the ink from evaporating, oxidizing, and dissolving bubbles, and maintain the stability of the ink composition in order to successfully complete high-quality printing; (3) High-line screen printing Ink roll: This is one of the most important conditions for high-line printing. The higher the number of reticulate lines, the higher the printable mesh line, and the smaller the amount of ink to be transferred, which helps to reproduce tiny high-gloss dots; (4 ) Suction and paper feeding, full absorption of paper: It can improve the flatness of paperboard, smooth the paper, ensure the accuracy, and ensure the accuracy of registration; (5) The liner (lining between printing plate and plate roller): better lining The pad cushions and adjusts pressure to protect small dots and increase plate life.