295. What are the thicknesses of the flexo? How is its application?
Flexo is usually thin and thick. The thin version mainly has several thicknesses of 0.67mm, 1.14mm, 1.70mm, 2.28mm, and 2.54mm, and is mainly used for the printing of flexible packaging, labels, folding cartons, paper bags and other products. The thick version mainly has several thicknesses of 2.84mm, 3.94mm, and 7.00mm, which are mainly used for the printing of corrugated boxes and other products.

296. What is the hardness of the flexo version?
In order to adapt to the requirements of various printing materials and products, there are usually many flexible plates with different hardness available. The higher the hardness of the flexographic plate, the smaller the dot gain at the time of printing and the higher the dot definition. The lower the hardness of the flexographic plate is, the more easily the dots are deformed, but the contact with the printing material is closer. The ink transfer performance in the solid area is good and the printing ink is more uniform. In the case where the field area coexists with the halftone image, a flexible plate with moderate hardness should be selected.
When the printing surface is smooth and smooth, the hardness of the printing plate is required to be high, that is, a harder, flexible plate is used. When printing a rough surface, the hardness of the printing plate is small, that is, a softer, flexible plate is used. In general, the hardness of a flexographic plate for corrugated box printing is HS 30-40, while the hardness of a thin plate is usually HS 40-70.

297. How to properly store the flexible version?
(1) Flexible plates should be sealed, protected from light, and prevent heavy pressure.
(2) Flexo should be stored in a cool, ventilated environment to avoid moisture.
(3) The storage time of the flexo plate should not be too long to be used within one year.
(4) After printing, the printing plate must be clean. After it is dried, seal it in a black plastic bag, place it horizontally or hang it in a cool, ventilated place for reuse.

298. How to clean the flexible version after printing?
The flexo should be cleaned immediately after printing, otherwise the ink will dry on the surface of the plate and it will be difficult to remove and may result in a bad version. For solvent inks or UV inks, use a low-concentration mixed solvent (such as alcohol) that matches the media. For water-based inks, use alkaline cleaners or high-quality cleaners for flexo printing. It is worth noting that when cleaning, apply a soft cotton cloth to gently wipe, and avoid using hard brushes to scrub to prevent the plates from scratching. After washing, dry the plate with a lint-free cloth, taking care not to repeatedly rub the plates, and then dry them for later use.

299. Why do you want to make deformations and shrinkages when you make plates?
The distinctive feature of the flexo plate is its elasticity. After being mounted on the plate cylinder, the flexo plate will be stretched and deformed along the circumferential direction of the plate cylinder. After the printing, the graphic text will also be elongated and the original will not be reproduced correctly. Therefore, in order to eliminate this phenomenon, the plate-making data file must be subjected to unidirectional shrinkage processing in the printing direction when designing the plate-making process. The graphic and text on the produced film and printing plate are also reduced in one direction and can be obtained after printing. Original large-size graphics required.

300. How to calculate the reduced version of the flexo version?
The shrinkage of the flexographic plate is related to the diameter of the plate cylinder (including the double-sided tape) and the thickness of the plate itself. In general, the larger the diameter of the plate cylinder, the smaller the thickness of the plate material, the smaller the amount of elongation deformation of the plate, the smaller the amount of reduction. The compensation percentage of the reduced edition can be calculated by formula (1).
Minor volume compensation percentage=K÷R×100% (1)
Among them, K is a constant, which can be found in Table 1. R is the printing perimeter of the plate cylinder (including double-sided tape). When the plate cylinder has a 1/8 inch gear module, R = the number of teeth of the plate cylinder × 3.175.
For example, a 98-element plate cylinder is required for printing a certain product, and the plate thickness is 1.70 mm. The calculation result of the reduction percentage of the reduction is as follows.
Reduced edition compensation percentage = 9.89 ÷ (98 × 3.175) × 100% = 3.18%
It needs to be further explained that in actual production, due to numerous factors, the prepared printing plate is calculated according to formula (1), and the printed matter after printing may not reach the expected size requirement. In this case, the actual measurement test reduction rate should be performed, as in equation (2).
Reducing ratio = (text length of printing plate or film, actual length of printed matter) × 100% (2)

301. What are the dot gains? How did it come about?
Dot enlargement refers to the phenomenon that the dot on the film or plate increases after printing. The dot gain rate measured by the test instruments such as the density meter consists of the mechanical dot gain rate and the optical dot gain rate, as shown in FIG. 1 . The optical dot gain is caused by light reflection and is an inherent optical phenomenon. The mechanical dot enlargement refers to the dot gain caused by the printing pressure. Usually, the dot gain is usually referred to as the mechanical dot gain. Big.
Due to the high flexibility of the flexographic printing plate, the dots on the printing plate may be deformed under the influence of the printing pressure, and the ink will spread outward along the edges of the halftone dots, thereby causing the dots to increase. Under different printing conditions, the dot gain rate is also different, that is, relatively stable dot gain rates can only be maintained under relatively stable printing conditions.

302. What is network compensation?
The prominent feature of flexographic printing is that dot gains are more serious, and the tone levels of prints are darker and darker. Therefore, in order to reduce dot gains and obtain high-quality prints, in addition to strictly controlling the printing conditions, it is more important to In the design of plate making, according to the change law of the dot gain rate, the data size of the printing plate dot is reduced accordingly. We call this dot dot compensation. The curve formed by 0-100% of the dot compensation value is called a dot compensation curve. The dot compensation curves of different color versions are also different.

303. Why do you want to make a print test version?
There are many factors that affect the quality of flexographic printing, such as the printing plate, ink, printing materials, flexographic printing presses, and the skill level of operators. In order to obtain high-quality flexographic prints, various factors are required to cooperate with each other. Therefore, it is necessary to fully understand and grasp the influence of these factors on the print quality in different situations. The printing test plate can fully reflect these printing characteristics, it can be used for the new machine's adjustment machine printing test, the new ink, the new material application test, also can use in the machine performance regular examination.

304. What basic test elements are usually included in a print test?
Flexo printing test plate generally contains dot gain test strips, ink density density test blocks, overprint test information, Yin and Yang graphic line test information, gradient test bar, pressure balance test information, gray balance measurement and control information, color management information Wait.

305. How does the dot gain test information in the beta version work?
The dot gain test information bar is generally composed of multiple gray scales with different color versions and different number of screen lines. Each gray scale ruler usually includes 2%, 3%, 4%, 5%, 10%, and 20%. 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 100%, etc. multiple connected gray-scale color blocks. In order to facilitate the instrument to read, the size of each gray-scale color block is generally greater than 3mm x 3mm.
Using a reflective densitometer and other test equipment to measure the color blocks on the gray scale one by one, the dot gain rate corresponding to each gray scale value of different color plates and different screen lines is obtained, and thus dot data of the printing plate can be compensated.

306. How does the ink field density value in the test version work?
In flexographic printing, due to changes in the ink, printing materials, printing presses, and operators, there will be some changes in the density of the ink after printing. Usually we hope that under normal printing conditions, the field density value can remain relatively stable, which helps the printing of data control and accurate reproduction of halftone images.
The solid density target values ​​for four-color inks are usually as follows.
Yellow: 1.00 to 1.10 Magenta: 1.20 to 1.30
Blue: 1.30 to 1.40 Black: 1.50 to 1.60
Under the premise of controlling the dot gain rate to be smaller, the field density value should be as close as possible or reach the target value. At the same time, the performance of the ink can be judged based on the density of the ink in the field under normal printing conditions.

Source: Ke Yin Media - "Printing Technology - Packaging and Printing"