Analysis on the transfer and transfer of the hotte

Analysis on the transmission and transfer of offset printing ink

the printing process is the process of ink transmission and transfer. How can we make the ink transfer correctly according to the needs of the production process? What are the factors that affect the ink transfer effect? How should they match

I. transfer of offset printing ink

1. Transfer from ink bucket to ink bucket roller. The ink in the ink bucket is always in good contact with the ink bucket roller, so that the ink can be evenly sent out by the ink bucket. This mainly depends on the rheological properties of the ink: thixotropy should not be too large, yield value should not be too high, viscosity should not be too small, wire head should not be too short, rheological properties should be good, etc. If the ink in the ink bucket has high yield value and low viscosity, its inkability is poor, because it lacks the necessary adhesion ability to the ink bucket roller, so it must often pull out the ink bucket to ensure good contact between the ink and the ink bucket roller, otherwise it will cause the front depth and back light of the printed matter due to the gradual separation of the ink and the ink bucket roller. In addition, we should also pay attention to the ink storage in the ink bucket, which should be kept within a certain range, and strive to make the ink uniform

2. Transfer from ink bucket roller to ink roller. Because the ink bucket roller of offset press rotates intermittently, the ink output by the ink bucket roller is always an arc-shaped strip of ink, and the width of the ink strip can be adjusted. In the printing process, the transmission mode of thin ink layer and wide ink strip is better than that of thick ink layer and narrow ink strip, which can make the ink be evenly beaten as soon as possible. After the ink is transferred from the ink bucket roller to the ink roller, whether the ink can be beaten evenly quickly depends on whether the number and diameter of the ink roller are prime numbers, whether the ink transmission route is reasonable, whether the water and ink are balanced, and whether the surface adsorption of the ink roller is good

the inking devices of offset press are mostly long ink path devices, which use more than ten ink rollers to complete the transmission of ink. In addition, the radial runout of the inking roller and the axial series movement of the inking roller will subject the ink to a certain amount of radial and axial shear stress. During the transmission process, the ink will release a lot of heat after being squeezed by the ink roller, which will increase the ink temperature. For example, when the workshop temperature is 25, the ink temperature on the ink roller will reach 40 ~ 50 after the machine runs continuously for half an hour

3. Transfer from inking roller to printing plate. During offset printing, the printing plate is wetted by the inking roller first, and then the inking roller is in full contact with the printing plate to supply ink to the graphic part of the printing plate. Generally, when the water film of the printing plate is 1mm, it can prevent the ink on the ink roller from inking on the blank part. If the water film on the blank part of the printing plate is too thin, it will get dirty. If the water film is too thick, the ink emulsification will be excessive. Therefore, too much water supply will damage the effect of ink transfer from the ink roller to the graphic part of the printing plate, so we must control the ink balance

II. Transfer of offset printing ink

1. Conversion from printing plate to blanket. As offset printing is indirect printing, the ink of the graphic part of the printing plate must pass through the blanket to be transferred to the surface of the substrate, so it is required that the surface of the blanket should have good lipophilic and hydrophobic properties, and there should be a reasonable and uniform pressure between the blanket and the printing plate. When the graphic part of the printing plate is transferred to the blanket, the protective effect of the graphic part of the printing plate should not be underestimated, It is also indispensable

2. Transfer from blanket substrate. When the imprinted ink layer is transferred from the blanket to the printed matter, the pressure between the blanket and the substrate should be uniform. The ink receiving performance of the substrate itself should also be good, and it should have sufficient strength. The surface should be smooth and the thickness should be uniform in order to print a good product

the transfer of imprinted ink to the surface of the substrate can generally be divided into three steps: the initial stage of contact transfer between the imprinted ink layer and the substrate. The imprinted ink layer is squeezed by the pressure of the printing plate, and the ink is pressed into the uneven pores on the surface of the substrate

-- cavitation and fracture of imprinted ink layer. At this time, the ink layer is stretched and broken due to centrifugal force and cavitation, but due to the good wetting property of the ink on the substrate surface, part of the imprinted ink layer is transferred to the substrate surface. After the imprinting ink layer is divided into two, the imprinting ink transferred on the surface of the substrate continues to penetrate into the paper through the adsorption of pores. For the substrate with smooth surface and little absorption, high-performance separation membrane technology is planned in the direction of new functions and intelligent materials. Imprinting and then putting a large number of reusable and valuable materials into the project again, and putting them into the dryer to preserve whether the ink layer can be adsorbed on the substrate surface, which is mainly faster than the affinity of the substrate surface to the ink and the force between the ink and the substrate molecules

3. Fixation, drying or retransfer of the imprinted ink layer on the substrate. Offset printing ink is an ink with oxidation polymerization conjunctiva as the main drying form. Its drying process is generally divided into two stages: fixation. Ink from liquid to semi-solid, no longer flow transfer, also known as the initial stage of ink drying

-- dry conjunctiva. There are many experimental machines in the semi-solid ink. Purchasers have misunderstandings in the selection of experimental machines. Physical and chemical changes have taken place in the material connection, which makes the ink completely dry and conjunctive. This is the complete drying stage of the ink. However, during the printing process, the imprinted ink transferred on the surface of the substrate will also suffer from rubbing, chalking, through printing, crystallization and other faults due to various reasons. Therefore, the possible faults should be fully estimated in advance and necessary preventive measures should be taken