Factors affecting the transfer of ink by the anilox roller
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Since the development of flexographic printing, the ink transfer method of its printing equipment has undergone continuous improvement and improvement with the development of science and technology. If it is still at the level of the original metal roller and metal anilox roller, it is difficult to meet the standard requirements for the amount of ink required for various types of printing developed in Japan. At present, flexographic printing has been able to produce high-quality prints. It is also recognized that ceramic anilox rolls have contributed to the development of flexo printing. It is the unit of each ceramic anilox roll. It is still unable to achieve uniform data and consistent ink transfer, resulting in more ink transfer of the same number of anilox rolls.
(BCM is the standard for the transmission of ink in the United Kingdom and the United States. In Western Europe (except for CM3/M2 outside the UK, the conversion method is 1BCM=1.55CM3/M2) or the number of different anilox rolls and the amount of ink transferred are the same, which affects the use and communication. The chaos. This article can theoretically explore the factors affecting the amount of ink transferred (transferred) by the anilox roller in order to grasp the relationship between these elements and the amount of ink delivered, in order to use the anilox roller handy.
The elements of the anilox roller to transfer the ink amount include: the number of mesh rolls, the ratio of opening to mesh wall, the shape of the cell, the depth of the cell, the running speed of the surface of the cell surface, the angle of the wire, and the shape of the dot.
1. Anilox roller line
The number of anilox rolls, that is, the distribution of the cells in the unit length, can be calculated according to the distribution of the cells per unit area. Here the unit length refers to each inch (2.54 cm), such as 200 lines / inch, that is, every 200 cells (800 cells / cm), 10,000 cells. The same line of 500 lines / talent, there are 250,000 cell sites. Since the single area is the same and the number of the same holes is different, the size of the cells is different, the amount of stored ink is large, and the amount of ink transferred is also large; the small is the opposite, so the amount of ink transmitted by the high line is less than that of the low line. Some units have already done exploration experiments. The ink is transferred by an anilox roller of 1000 lines/inch. As a result, the density value of the ink does not reach the "international" requirement. Here, a problem is explained: the number of the anilox roller lines should be reasonably selected, and the higher the better, the better.
At present, there is still a tendency to increase the number of anilox rolls, which specifically reflects that the number of anilox rolls is high and the machine quality is good. 2 When purchasing a machine, pay more attention to the anilox roller with a high number of lines. 3 Anilox rolls are machined to 1200 lines or even 2000 lines, and the quality of the anilox roll is exaggerated. 4 corrugated carton printing slot selection of ceramic wire rolls of 350 lines / inch or higher. The author thinks that it is wrong to measure the quality and printing performance of the anilox roller by the number of anilox roller lines. The number of lines of the anilox roller is exactly the amount of ink. Under normal circumstances, the number of lines is high and the amount of ink is small. When the number is low, the amount of ink is large.
The anilox rolls have different numbers of lines, which gives the flexo workers a choice of ink control, and also creates conditions for high print quality and high network products. Metal anilox rolls can only be processed to 300 lines/inch, so only 120 lines/inch of flexographic prints can be printed before the 1980s, and 175 lines/inch of prints can be printed later. Ceramic anilox work No. Here also raises a question, how high is the number of ceramic anilox rolls? At present, according to the author's knowledge, the country's highest selection of 1000 lines of foreign 1200 lines, 2000 lines will be how real, the key is that the amount of ink is very small, this is not up to the use requirements. When the number of anilox roller lines is selected, in addition to the conventional principle (base material, text, image line number, ink), it should be emphasized that each unit chooses to adjust in practical applications. In the future, with the improvement of the texture roller processing technology. The amount of ink stored in the cell will increase, and the number of lines used in the anilox roller can be appropriately increased, but the anilox roller above 1000 lines should be used with caution.
2. Opening to mesh wall
This factor has a certain relationship with the amount of ink transfer, the depth of the cell and the ratio of the number of printing plates, but the ratio of the opening to the wall is unlikely to increase a lot. Otherwise, the service life of the same roller will be affected. At present, the proportional parameters are not uniform.
The anilox roller transfers ink from the cells and the cells are concave. Therefore, there must be a mesh wall between the cells. The ratio of the opening to the width of the mesh is 5:1. In this case, the area of the mesh wall should occupy the whole 31% of the anilox roll. There is no ink on the mesh wall, especially in the case of using a doctor blade. If the anilox roller is used as a gravure plate cylinder, then the printing plate is a flat net, which means that the anilox roller is transmitted by the cell. Ink, is a point of ink. It is not a face-to-face ink, so this part of the wall is not ideal for transferring ink. If the high-gloss dot falls on the wall, you will not get ink.
Nowadays, some ceramic anilox roller processing units, according to the characteristics of high hardness and good wear resistance of ceramics, minimize the area of the mesh wall and improve the ink transfer effect. The method is to increase the ratio of openings to mesh walls, ie 7:1, 8:1 or even more than 10:1. Some units are introduced according to the range of the network cable. The low network cable is 200 lines/inch, and the high network cable is 800 lines/inch. This is scientific, and it is possible that all the lines are taken in a ratio, and it is impossible that the ceramic wall has high hardness and wear resistance, and the mesh wall can be finely and unrestricted. The mesh wall is not very vertical and its top is very thin. It can be seen from Table 1 that most of them do not reach 0.01 mm (the thickness of the newspaper is 0.07 mm). To affect the service life. According to the number of lines, the ratio of the opening to the mesh wall, the thickness of the mesh wall is known.
3. Cell shape
This element is still being improved after the successful research of ceramic anilox roller. It can be seen from the figure that the volume of the cell is expanding, why should it be expanded? Is the shape of the first cell not very good? The strength of the mesh wall is also high. From the third shape, the strength of the wall is greatly weakened, and from the table 1, the thickness of the mesh wall is still less than a trace of rice, but people still tend to expand the cell volume. :1 The role of the anilox roller is to transfer the ink, and the amount of ink transferred by the anilox roller should be increased as much as possible. 2 The depth of the cell can not be very deep, to maximize the cell volume within the effective depth. 3 As mentioned before, the anilox roller is a point transfer ink, not a surface transfer ink, and the ink transfer system of the flexographic printing has only one anilox roller and the plate roller. Although the mechanical structure is simple, it is in contact with the four plate rolls of the lithographic printing plate and the printing plate, and the anilox roller has sufficient ink transfer amount to achieve normal printing. 4 is conducive to the use of high anilox roller ink transfer, the shape of the cell is one of the key. 5 is beneficial to increase the ratio of the number of printing lines to the number of anilox rolls. The ratio starts at 1:3, and the ceramic anilox roller is improved after the application, generally 4.5 or more. The purpose is that the highlight point on the printing plate is enough to cover a few ink dots on the anilox roller, thereby ensuring that the high-gloss dot is sufficient. The inks, resulting in halftone products, are rich in layers and strong in appearance. According to the data, the ink storage capacity of the second type of cell can be increased by 10% to 15%, and the third type of ink storage can be increased by 20% to 30%. The shape of the cell is related to the service life of the ceramic. Therefore, it can be appropriately selected according to the actual needs according to the actual needs.
4. Cell depth
This element is also one of the key points. According to the data, the depth of the cell is 23% to 33% of the opening width, and 28% is ideal. This parameter is worthy of negotiation. According to this parameter, the 1000 line/inch ceramic anilox roller has a cell depth of less than 0.01 mm, which is almost the same as the top of the mesh wall, and the amount of ink transferred is very small. Therefore, this parameter is more suitable for metal anilox rolls. Because the metal anilox roller adopts the method of electronic engraving or the mechanical extrusion method of the hob, the depth of the cell is required to be separated from the cell by the knife and the hob, so it is impossible to exceed 1/2 of the opening width. It is impossible to make it bigger, so it is concluded that 28% is an ideal conclusion.
The ceramic anilox roller is processed by laser beam, and there is no requirement for the cutter to be detached. Therefore, the processing depth can be increased in an appropriate amount and can also meet the requirements for use. For example, the same cell can use two or more laser beam ablation mesh formation to achieve the desired depth, but this depth is not yet unified, and there should be an optimal value unified in the future.
In addition, according to the principle of velocity gradient of fluid mechanics, the ink in the cell cavity has a velocity of 0 near the wall of the cell wall, that is, stationary, which is often referred to as the Coanda effect, so the general ink release amount is 2/3 of the cell volume. ~4/5.
The depth of the cell is largely limited by the number of anilox rolls, and depending on the number of lines, the opening is compared to the mesh wall, the opening to depth ratio, and the depth can be calculated.
Example: The same pattern roller is 1000 lines/inch. The ratio of opening to mesh wall is 7:1, and the ratio of opening to depth is 1:1; thus, the depth of the cell is T=25.4/1000*7/8 *1=0.022
5. Cell surface smoothness
This indicator is very important in the metal anilox roll period, except that the shape of the same hole is required to be clear and uniform. The surface is smooth, and it is also required to be coated with a layer of chrome, on the one hand to improve the surface hardness of the anilox roll, on the other hand, the mesh is smooth and easy to apply. Early ceramic anilox rolls were very poor due to technical conditions. The surface finish was very poor, and the lava at the time of the explosion was observed under a high magnification magnifier. The surface is uneven, which affects both the ink release and the ink. Therefore, the cleaning liquid and equipment of the ceramic anilox roller should be cleaned by the anilox roller, but the requirements are not high.
Some units apply high-tech, such as ion implantation technology and nanotechnology, to change the performance of the ceramic layer, so that the relatively loose ceramic molecules become dense, thereby improving the surface smoothness of the cell surface, easy cleaning and improved service life.
Practice has proved that the poor surface finish of the cell cavity causes the ink transfer volume of the anilox roller to gradually decrease, and finally the use and product quality are printed. One unit prints the same batch of products before and after, and the printing plate, ink and base material are the same. However, the color difference was found, and it was found that the amount of ink transferred was reduced due to the clogging of the anilox roller. A corrugated box printing unit. Due to the blockage of the anilox roll, the indicator has been taken seriously by the manufacturing unit.
6. Anilox roller running speed
The amount of ink delivered by the flexographic printing anilox roll varies with the printing speed, and it should be clearly recognized and mastered as a flexo worker. The single scraper system has a high speed and a large amount of ink transfer; the double scraper seal system has the opposite effect, and the vehicle speed is high and the amount of ink transfer is small.
Flexographic printing started late in China, and there are not many skilled operators at present. Many units are gradually improved by the running speed after the running-in. With a single scraper system, if the color difference is developed in the deep direction, measures should be taken to reduce the amount of ink transferred, increase the number of lines of the anilox roll, or reduce the hue of the ink.
7. Cable angle and mesh shape
The anilox roller is flat and ink-transfer, so the cable has an angle. The meshed wire has 30°, 45°, 60°, but the actual metal anilox roll is 45°, and the laser-engraved ceramic anilox roll is 60°. The 60° intensity is the best and the ink transfer amount is large. The ink transfer system of flexographic printing is developed from metal anilox roller to porcelain anilox roller, and the metal anilox roller is convenient to process 45°, and the half color is formed to meet the requirement of 45° of anilox roller, so metal and ceramic mesh The angle of the wire of the roller is not unified.
In the development of anilox rolls, many dot shapes have been used. Hexagon, quadrangular, grooved, slanted, dot, etc. The grooved, slanted type is suitable for coating, but has been eliminated.
45° dot-shaped dots, the net product is more than hexagonal and quadrangular, which is unfavorable for the ink delivery, and is also eliminated by the dot shape. At present, the metal anilox roll dot shape is a quadrangular shape, and the mesh line degree is 45°. The ceramic anilox roll has a hexagonal shape and a mesh angle of 60°.
Among the above 8 points, except for the sixth point, it has nothing to do with the processing. The other 7 points have 3 points which are constant (the number of anilox lines, the angle of the net line, the shape of the dot), 4 points (the ratio of the opening day to the net wall, the shape of the cell. The depth of the hole and the surface finish of the cell have not been agreed by the processing units, so the ceramic roller of the same number of lines has an inconsistent amount of ink delivered.
According to the data, the anilox rolls of different lines have the same ink, such as BCM7-8, and the number of anilox rolls is 200~3BCM3.5. The number of anilox lines can range from 400 to 700 lines. This choice is for AC. If halftone is printed, does BCM require 3.5 lines or 700 lines? Will the selection of the 400 line violate the proportional relationship between the number of printing lines and the number of screen lines? Will there be moiré?
The laser light source for processing ceramic anilox rolls has CO 2 and YAG, and other light sources will appear in the future. The light source is different and the characteristics of the cells are different. As described, ceramic anilox rolls now have the same amount of ink delivered due to different processing parameters.
Therefore, the author's point of view is: 1. At present, each unit should understand the principle, function, and BCM of the palm print roller; 2. According to the current loop line, the BCM is not unified, and the range of the BCM range is large. BCM should be the main one, the number of anilox roller lines can not be used as the basis for adjusting the ink; 3. In practice, it is more reasonable to choose and be good at adjusting BCM ink, and communication is a reference; 4. I hope to do only one in the future. A kind of ink transfer quantity (BCM), the amount of ink changed by the network line also follows, so that it can adapt to the use and selection of the anilox roll and communicate.