Application analysis and maintenance of flexographic anilox roller
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The full name of the anilox roll is the anilox roller, which is a very fine and very important part of the flexographic ink transfer part. What is the role of the specific anilox roll? What are the parameters of the anilox roll? And how should the anilox roller be used and maintained?
First, the structure and type of anilox roller
From the surface structure of the anilox roll body, it mainly consists of two parts: the mesh and the mesh wall; from the structure of the anilox roll, it is mainly composed of the roll core, the base material and the surface plating. The commonly used material for the base material is electroplated copper, which is the basis for making the anilox roll mesh and mesh wall; the surface plating is made of metal chrome or ceramic, which mainly improves the abrasion resistance of the anilox roll and the corrosion of the base copper layer by the barrier solvent.
According to the different coating on the surface of the anilox roller, it can be divided into metal chrome-plated anilox roller and ceramic anilox roller. From the comparison of engraving precision, printing durability and ink-discharging performance, ceramic anilox roller has more advantages, so the enterprise More ceramic anilox rolls are used.
Metal anilox roller processing process: metal roll base → copper plating → engraving → chrome plating
Ceramic anilox processing process: metal roll base → copper plating → engraving → sandblasting → ceramic material spraying → polishing
Metal Roll Base → Coated Ceramic Material → Polishing → Laser Engraving
Because the chrome or sprayed ceramics after engraving will lead to the reduction of the mesh volume of the anilox roll, the method of first spraying the ceramic and then laser engraving can ensure the accuracy of the anilox roll, which is also the use of ceramic anilox rolls. One of the reasons.
Second, describe the parameters of the anilox roller
The role of the anilox roller is to quantitatively and evenly transfer ink to the portion of the plate. The determinant of whether the anilox roller can deliver the ink quantitatively, uniformly and accurately depends on the parameters of the anilox roll.
1. Cell shape
The shape of the cell has a quadrangular pyramid shape, a quadrangular prism shape, a hexagonal prism shape, a spiral shape, and the like. At present, most of the quadrangular pyramidal meshes exist on the metal anilox roller, which is completed by electronic engraving; the hexagonal prismatic mesh is mostly found on the ceramic anilox roller, which is made by laser engraving, compared with the quadrangular pyramidal mesh. The hole has the characteristics of storing more ink and better ink transfer performance.
2. Number of lines
The number of mesh lines is different from the number of dot lines. It is defined as the number of cells in the unit length along the axial direction of the anilox roll, and the unit is line/inch or line/cm. Another point that the number of mesh lines is different from the number of dot lines is that there is no direct correspondence between the number of mesh lines and the sharpness of printed graphics, but it affects the quality of printed graphics.
3. Netting angle
The anilox rolls made by electronic engraving can engrave 30 o, 45 o, 60 o cavities respectively because of the angle of the engraving knife. Laser engraving usually engraves a 60 o-six-deformed cell.
4. Cell opening, depth, opening degree
The opening of the cell refers to the width of the surface opening of the cell, which is usually represented by b; the depth of the cell refers to the depth of the cell, which is usually represented by H; the opening of the cell refers to the depth of the cell (H) and the opening of the cell. The percentage of (b) is usually between 23% and 33%, and the best is 28%.
5. Cell volume
The cell volume refers to the total amount of ink that can be contained per unit surface area of the anilox roll, and the unit is BCM/in2 (B-Billion; C-Cubic; M-Micro). It is a parameter reflecting the amount of ink stored in the anilox roller, and is converted to a domestic unit, 1 BCM/in2 = 1.55 cm 3 /m 2 .
Third, the factors considered when using the anilox roller
1. Choose the appropriate cell volume
The size of the volume directly determines the amount of ink supplied by the anilox roller. Different grades of printing require different amounts of ink supply. Therefore, the volume of the cell should be fully considered when selecting the anilox roller. 2. Select the appropriate number of mesh lines
In general, the amount of ink supplied to the anilox roller decreases as the number of netting lines increases. The higher the number of netting lines, the smaller the amount of ink supply, and the better the relative uniformity. For a single cell, because the shape of the cell determines the presence of the corners inside the cell, it is also due to the presence of the corners of the cell, which leads to the hindrance of the cell to the ink transfer, namely the "corner effect". The higher the number of mesh lines, the more the number of cells in the unit length, and considering the factor of the mesh wall between each two cells, the higher the number of mesh lines in the same volume. The greater the degree of opening, that is, the greater the relative depth, the more serious the corner effect, resulting in a reduction in the amount of ink transferred. Therefore, the amount of ink supply should also be fully considered when selecting the number of lines.
① consider the fineness of the print
Relatively speaking, the field, the line, the text, etc. require a large amount of ink, and the number of selected mesh lines is relatively low; the color network line pattern requires a small amount of ink, and the number of selected mesh lines is high (as shown in Table 1). In addition to the amount of ink supply, consider the number of dot lines on the plate. The fineness of the printed matter depends on the number of dots. On the plate, after the dot size is determined, if a lower number of anilox rolls are used, the area of each cell will be larger than that of some dots on the plate. The area, when printing, the mesh point is not supported by the partition wall, the dot will be immersed in the cell, not only the surface of the dot is inked, but also the sidewall will be inked, resulting in an increase in dot size, for example, for an area ratio of 80% dot. Color patches can cause paste to die, print to the ground, and cause edge ghosting failures. Practice has proved that in order to obtain superior quality printing, the number of mesh lines of the anilox roller and the number of dot lines of the printing plate are maintained at a ratio of about 4:1.
② consider the printing materials and printing requirements
Different printing materials have different ink absorption properties, and different printing materials have different drying methods. Therefore, the factors of ink demand of printing materials should be fully considered. Generally, the ink absorption is large, the number of selected mesh lines is low, and the ink absorption is small. The number of selected mesh lines is high.
3. Choose the right shape of the cell
① with the ink supply form
The ink supply form of flexographic printing is mainly divided into two types: a double roll type and a scraper type, wherein the scraper type can be further divided into a forward scraper, a reverse scraper, and a fully enclosed double scraper. Under the same number of lines, the volume of the quadrangular pyramidal mesh is rapidly reduced by the scraper wear. Therefore, the quadrangular pyramidal mesh is mostly used in the form of a two-roller ink supply. The quadrangular table and the hexagonal table can be used in the scraper type.
② with the ink type
The slanted mesh cavity improves the ink transfer property of the anilox roller because it can ensure the fluidity of the ink. Therefore, for inks with higher viscosity, or varnish, paint, etc., a diagonal linear anilox roller can be used for ink supply.
4. Choose the right mesh angle
In most cases, a 60o, regular hexagonal ceramic anilox roller is selected for ink supply, and other angle anilox rolls are used only in special cases.
In addition to the above factors, it is more appropriate to choose which type of anilox roller is suitable in combination with the actual needs of the enterprise, for example, considering the cost of the enterprise.
Fourth, the maintenance of the anilox roller
The anilox roller is the most precise part on the flexographic printing machine. Paying attention to the maintenance during daily use is an important part of extending the service life of the anilox roller.
1. Anilox roller cover is used when the anilox roller is stored
The use of the anilox roll protector, on the one hand, plays a better role of buffering and absorbing vibration, on the other hand, it can well keep the surface of the anilox roll clean.
2. Detect the viscosity of the ink and clean the anilox roller in time
The reason for the blockage of the anilox roll is, on the one hand, the nature of the ink itself, such as drying too fast; on the other hand, the cause of cleaning, such as incomplete cleaning or improper cleaning. Therefore, it is necessary to pay attention to keep the viscosity of the ink constant during the printing process. When cleaning the anilox roller, it is essential to use a cleaning method with less damage to the anilox roller and timely cleaning.
3. Using high quality scraper and magnetic filter
Using a high-quality scraper and controlling the pressure between the scraper and the anilox roller, the magnetic filter is placed in the ink tank under the condition of the condition, thereby reducing the impurity particles in the ink, reducing the wear of the anilox roller and prolonging its Service life.
4. Regularly check the cells with a mesh microscope
Use a mesh microscope to regularly check the cells. If you find scratches or blockages on the anilox roller, take timely measures.