Manufacturing and technical conditions of the hott

2022-08-06
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Manufacturing and technical conditions of metal ink transfer roller

with the rapid development of modern science and technology, as the flexographic printing technology is becoming more and more mature and widely used in the printing process of corrugated boxes, the corrugated roller, as the most critical functional component of the flexographic printing machine, its manufacturing technology, manufacturing precision and variety are also developing rapidly to adapt to the wide, high-speed and Multi color and high-grade color tone flexo printing development needs. With the characteristics of low production cost, short processing cycle, durability, high precision and wide selection range, as the largest family of corrugated rollers, metal corrugated rollers are widely used in the medium and high-grade medium and high-speed corrugated box flexographic printing machines with the largest number and most common use

I According to the different manufacturing methods, there are three kinds of metal striated rollers: one is made by the process of photographic film plate printing, the other is made by computer-controlled electronic engraving after copper plating on the steel roller, and the other is made by mechanical extrusion directly on the surface of the steel roller with striated cutters. The corrugation roll is not suitable for use in the corrugated box printing process because its manufacturing process will make the roll surface have seams, which will cause uneven ink volume, and it is not easy to corrode the lines with more than 100 lines/inch. The application of copper plated engraving roller is limited due to its soft grain surface, no pressure resistance and wear resistance, no resistance to alkaline water-based ink corrosion, and shallow engraving depth

at present, the metal ink transfer rollers commonly used in corrugated box flexographic printing machines are all manufactured by mechanical extrusion process, and their accuracy is mainly guaranteed by the manufacturing process and extrusion technology of corrugated cutter and roller. At present, the process level of manufacturing metal textured rollers by mechanical extrusion in China is uneven. The main difference lies in the accuracy of cutting tools, the machining accuracy of rollers and textured extrusion technology. Check the inferior metal ink transfer roller with a 25X magnifying glass. The lines are rough and unclear, and the holes are shallow, the wall width and the number of lines are inaccurate. In addition, the small thin plate called strain gauge manufactured by the roller has low dimensional and geometric tolerance accuracy and poor balance after the electrical signal is transmitted after deformation, so the use effect is poor

the mature process technology is enough to ensure that the number of lines of the metallic ink transfer roller with the surface length of more than 3000 mm can reach 300 lines/inch, the cylindricity is less than 0.016mm, and the radial circular runout is less than 0.02mm. The inspection with a 25X magnifying glass shows that the lines are clear and bright, the wall is narrow, and the edges are neat, so it has excellent ink storage, ink uniformity, and ink transfer performance. The metal embossed roller must also have good pressure resistance, wear resistance and corrosion resistance. By using the most advanced heef-25 high-efficiency micro crack electroplating hard chromium process in the world, the surface of the embossed roller can obtain a hard chromium coating that is harder, smoother, brighter and more wear-resistant than the ordinary hard chromium coating. Its microhardness reaches hv900 ~ 1050, and the number of micro cracks per square centimeter of the coating reaches more than 400, The metal ink transfer roller with this process has excellent corrosion resistance, wear resistance and pressure resistance. The metal embossed roller manufactured by this process has been used by famous medium and high-grade medium and high-speed corrugated box flexographic printing machines and manufacturers at home and abroad for a long time, and has achieved good results

II Functions of the metallic ink transfer roller

the surface of the metallic ink transfer roller is processed into innumerable holes with uniform shape, size and depth arranged according to certain specifications. It plays the following functions in operation:

1. measuring and storing ink. The holes formed on the surface of the metallic ink transfer roller can accurately measure and store the ink. The volume formed by the holes with different specifications (shape, size and depth) is also different. According to different ink performance, ink receiving performance of printing materials and ink demand performance of printing content (color block area, line thickness, flexographic plate line), appropriate hole specifications can be selected

2. Ink leveling function. The surface of the metallic ink transfer roller is made into innumerable holes with uniform shape, size and depth arranged according to certain specifications, so that the transmitted ink is distributed very evenly. After being squeezed and scraped by the relatively running ink scraping rubber roller, a uniform ink layer is formed on the surface of the metallic ink transfer roller

3. Transfer ink function (see Figure 1). When the metal ink transfer roller (2) after the ink on the surface of the roller is squeezed by the ink scraping rubber roller (7) contacts the flexographic plate (3) pasted on the plate roller (6), most of the ink stored in the hole is evenly transferred to the surface of the flexographic plate (3) and printed on the corrugated box board (5) through the plate roller (6). The inking system of flexographic printing machine is composed of metal ink transfer roller, ink scraping rubber roller and plate roller. With each revolution of the metallic ink transfer roller, a complete functional process of metering, no progress, no innovation, no strong ink storage, ink leveling and ink transfer is realized

1. Ink 2 Ink transfer roller 3 Flexographic plate 4 Impression roller 5 Corrugated box board 6 Plate printing roller

7 In addition, it can resist the fatigue of vehicle body or attachment points. The rubber squeegee roller

III Technical conditions for metallic ink transfer roller

1 The structure of patterns (holes, walls)

patterns are composed of holes and walls. Holes are pits of the same size that are extruded into the same three-dimensional geometry (six cones, four cones, diamond cones, etc.). The interface between pits is called a wall. In order to obtain sufficient ink storage and delivery, the narrower the wall is, the better, so as to ensure the largest possible volume. Therefore, under the premise of ensuring the tool accuracy, the best depth must be achieved during machining

1. Acupoint 2 Wall drawing (2)

2 Shape of grain

different grain shapes on the metal grain ink transfer roller determine different volumes and ink storage and delivery volumes. Most of the grain shapes are square pyramid, hexagonal, pyramid, hexagonal connected, diamond, etc. With the same number of lines, the shape of the pattern is different, and the volume is also different. With the same number of lines, choosing the appropriate pattern shape can obtain a better printing effect

3. The number of lines of the pattern

we can regard the pattern as formed by the intersection of convex lines, and the number of convex lines per inch (25.4 mm) is the number of lines of the pattern, that is, the specification of the pattern. The more lines, the more holes per unit area, and the more uniform the ink layer. But at the same time, the smaller the hole is, the smaller the volume is, the thinner the ink layer is, and the amount of ink transfer is reduced accordingly

the line selection of the metallic ink transfer roller mainly depends on the actual ink demand of the printed product, generally between 165 ~ 300 lines/inch. 165 lines/inch can be selected for large-area field printing. Generally, it is carried out until it is broken. 180 ~ 300 lines/inch can be selected for 55 ~ 85 lines of color hierarchical flexographic printing. At the same time, there is an important relationship between the number of lines of the wrinkle roll and the number of lines of the flexo plate. The number of lines of the wrinkle roll must be 3.5 ~ 4 times of the number of lines of the flexo plate, so as to ensure that the minimum point of the highlight area in the flexo plate will not fall into the hole of the wrinkle roll and produce ink spots, which will affect the printing quality

4. The line arrangement angle of the metal grain ink transfer roller refers to the included angle with the axis of the roller. In general, the square pyramid shape and pyramid shape are 45 °, while the hexagonal, hexagonal connected and diamond shape are 60 ° and 30 °. Industry colleagues know that if the line angle of the wrinkle roller and the flexo plate coincides or the line number of the wrinkle roller is not in proportion to the line number of the flexo plate, printing will crack. Therefore, the line arrangement angle of flexo printing plate must avoid the line arrangement angle of the ink transfer roller

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