Development Analysis of Flexographic Printing Ink System
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Traditional printing is an industry that copies text and images on paper, plastic, metal and other base materials. There are hundreds of sheets and tens of thousands of sheets. The quality requirements are uniform ink, uniform depth, clear lines of text, no flowers. Not paste. The color image is colorful, rich in layers and strong in three-dimensional. Replica should be faithful to the original or conform to the natural color. Therefore, the traditional printing method has carefully considered and carefully designed the ink transfer system to meet the requirements of ink transfer.
Basic requirements for the ink transfer system: 1 There is a reasonable amount of ink, 2 the amount of ink should be uniform, and 3 can repeatedly supply the ink quantitatively. In this way, a large number of copies can be met. Otherwise, one is deep, one is shallow, the ink is deep and shallow, and the text and lines are thick and thin, which cannot meet the quality requirements.
In the early inkjet printing system of flexographic printing, the anilox roller was not used, so the ink color was very unstable, and only the products with low requirements were printed. The anilox roller was developed through continuous improvement in practice.
Flexographic printing ink transfer systems have begun to use rubber rolls, felt rolls, and metal light rolls. The rubber roller is made of natural rubber, its mechanical precision is not high, and the ink is difficult to control. Therefore, only rough and simple paper bags can be printed at that time; the felt roller is a feature that can absorb and discharge ink by using felt, but the felt has a short service life. Soon after use, the connecting material in the ink will make the felt hard, and the felt loses the characteristics of sucking and discharging the ink, so it is not ideal. Although the metal light roller has high processing precision, the gap between the two rollers can be used to control the amount of ink. However, due to the tension relationship of the ink, the ink will accumulate together, resulting in a strip of streaks, resulting in uneven ink transfer, so the printing quality. Not too high.
Later, some people used high-speed steel shot on the surface of the metal light roller to improve the hardness of the metal surface. The surface of the metal light roller was roughened and pitted. Although the properties of the metal light roller were changed, the ink did not easily accumulate, but the spray was not sprayed. The pill does not guarantee the depth and consistency of each roll; it has also been tried to sinter the ceramic on the steel roll to naturally form irregular pits, but it is not well controlled.
In the 1930s, due to the development of photographic and electroplating corrosion techniques, metallized rolls were etched by plating copper on steel rolls and then printing them with carbon paper or photographic film. This anilox roller can be controlled by the wire and copying process. Although it has taken a big step forward and laid the foundation for the development of the anilox roller, it is still not ideal: 1 There are seams, the amount of ink at the seam is not uniform, 2 The network cable is relatively thick, about 100 l/in or less, and is not easy to manufacture and corrode. In the early 1980s, when manufacturing a laminated flexographic printing press, the imported metal anilox roller was expensive, and the corrugated anilox roller was used. The development of things has always been improved and perfected. The development of anilox rolls has been improved according to the advanced processing techniques of different periods. After corroding the anilox rolls, copper plating on steel rolls has been applied, followed by mechanical engraving and The electronically engraved metal mesh roll has a metal-free roll that is ideal for seamless joints. However, the mechanical engraving speed is slow, and the electronic engraving is carried out on the steel (the Shanghai Printing Technology Research Institute has successfully developed and put into production the metal anilox roller directly engraved on the steel roller), and later developed the mechanical extrusion technology directly in the steel. The metal anilox rolls processed on the surface, the current electronically engraved and mechanically extruded metal anilox rolls are still widely used in corrugated box printing slotting machines, laminated flexo printing machines, and coating equipment.
Regardless of the metal anilox roll processed by electronic engraving or mechanical extrusion, the number of mesh lines is generally below 3O0l/in, which cannot meet the ink transfer amount of printed high-line products, and can only print 80l/in and 100l/in. The product therefore also limits the improvement and development of flexographic printing quality.
In the mid-1980s, laser technology was used to develop laser-engraved ceramic anilox rolls. Ceramic anilox rolls can process higher numbers of lines, have a wear-resistant surface, and can use a doctor blade to make the ink transfer system. The amount of ink transferred is more precise and stable, so the appearance of ceramic anilox roller not only further enhances the ink transfer system of flexographic printing, but also meets the requirements of printing fine products, which promotes the development of flexographic printing.
It is often said that the anilox roller is the heart of a flexographic printing press. As an anilox roller, it cannot form an ink transfer system in the printing machine. The early ink transfer system is rolled by two rollers, plus an ink disk, one of which is a roller. Contact with the plate and transfer the ink to the plate, so it is very simple to form the ink transfer system. Therefore, people also call the ink transfer system of flexographic printing as a short ink path, and the ink transfer system of offset printing is a long ink path. This structure has been extended to metal anilox rolls, and it still remains. Therefore, each color set of the flexographic printing press usually consists of four rolls (cylinder rolls, metal anilox rolls, plate rolls, embossing rolls), often referred to as 4-roll type.
Due to the advent of metal anilox rolls, it is naturally associated with gravure printing, which is very similar to gravure rolls. They are all made up of pits, and the surface is also plated with a layer of hard chrome. The method of squeegeeing with a squeegee is more accurate than that of the two-roller. Therefore, the characteristics of gravure and precise squeegee are naturally transplanted to metal. On the anilox roll, and the ceramic anilox roll has a harder surface, it is more suitable to use the doctor blade. Therefore, the ink transfer system of the flexographic printing has no ink fountain roller, only one metal anilox roller or ceramic anilox roller and The ink transfer form of the doctor blade, the squeegee is further improved from the forward direction into the reverse and two-way closed ink chamber, and the ink is supplied by the circulating pump to reduce the number of each color set of the flexographic printing machine from four rolls to three. Roller, it is also called three-roller.
At this point, the ink transfer system of flexographic printing has undergone practice- understanding - improvement - improve. Now it is now handy to properly arrange the anilox roller according to different printing bases and prints, becoming an ideal ink transfer system.