Ghosting performance characteristics (1) Infrequentity. In the printing, the appearance of ghosts is not common. No matter what kind of prints with graphic structures exist, there is a contradiction between ink and ink. However, not all prints have the appearance of ghosts, that is, in the printing of ink. Among them, there are some factors that inhibit the production of ghosts. What are these factors? We can use the traces of the reflow of ink to derive. First determine the amount of ink flowing back. The thickness of the ink layer of the offset printing product is 2μm. Calculated at an ideal ink transfer rate of 50%, the thickness of the ink layer on the blanket is 4μm, the printing plate is 8μm, and the printing roller is 16μm on the printing roller. The corresponding pressure in each zone on the reel roller causes a maximum deformation of only 16 μm, while the reel roller is the source of the reflow ink. The reflow ink layer is also the thickest, so the reflow causes deformation in the entire ink circuit system. The maximum change is 16μm. Compared with the thickness of the ink layer to ink. According to the simple calculation of the SM ink path, the ink layer thickness of the ink distribution roller connected to the ink transfer roller is at least 512 μm, and the ink volume of the ink roller is much larger than the ink transmission end, and the ink is actively changed to the ink end. The ability to deform the channel is much stronger than the ability to passively change the ink-transmitting end and deform the channel. This is because the ink layer is too thin to suppress the formation of ghosts. The second factor is the self-regulating ability of the ink road to ink volume. The ink path has a certain coefficient of ink storage, and has a certain self-regulating ability for the amount of ink in the ink path. When the backflow of the ink from the ink transfer end causes the ink path to accumulate too much ink, the ink is applied to the ink end of the ink. The road is no longer complete Accept the ink from the transfer roller. This is the self-regulation of the ink road to suppress ghosting. Again, the ink roller is axially shaken. When the remaining ink of the printing roller rewinds, the ink roller will evenly balance the remaining ink, so that the ink of the remaining ink is even, and the remaining ink difference of each area is reduced, so that the pressure difference is reduced and the channel is reversely changed. The degree of reduction. This is for the axial movement of the ink roller to reduce the deformation of the channel and suppress ghosting. Furthermore, the inconsistency of each ink roller in the ink path. The inequality of each ink roller originally makes the force point of each ink roller not overlap, and the formation of a ghost image is not easy to form due to the suppression of various factors, and it is due to the accumulation of the ink volume to deform the channel. Deformation of the channel should have more pressure, and because the ink layer on the printing plate is too thin and the pressure is not enough, there must be overlap of pressure points to accumulate pressure. This is the inequality of the ink roller which cumulatively reduces the pressure required to form a ghost to suppress ghosting. The inhibition of these factors makes ghosts uncommon. (2) Suddenly appears, suddenly disappears, and has a short duration. Ghosts appear suddenly because the pressure accumulation required for the deformation of the ink channel reverse control channel reaches a certain value, and the deformation of the reverse control channel causes the ink volume to change to produce a ghost image without changing the previous printing conditions. The setting is not what we foresee, so suddenly. The sudden disappearance of ghosts is due to a number of factors in the ink path that inhibit the formation of ghosts. Once a ghost is formed, each inhibition in the ink path self-adjusts in the ink path, and the process of adjustment is not We know it, so disappearing makes us feel suddenly. The short duration is due to the fact that the control in the ink path is controlled by both the active control deformation and the reverse control deformation. At the same time, contention occurs, and the active control is much stronger than the reverse control capability. The reverse control must obtain the control right. After long-term accumulation of power, once power is accumulated to a fixed value to gain control, it is also releasing strength, and after release of power, it must be delivered to active control. So the ghost formation has a short duration. The key-frequency accumulative force of ghost formation is due to the small amount of residual ink returning, which causes a small amount of change in pressure difference, so the key to the formation of ghosting is the accumulation of small pressure, and the accumulation of small pressure is not easy, due to the ink roller The range of the ink roll is such that the accumulated position of each pass of pressure does not overlap. If the A roller and the B roller are not equal in diameter, the two are X, Y, and both are pressed. There is a D force point on the A. The first D point is transmitted to the B roller D point, and the second D point is transmitted again. At point D, both A and B rolls rotate X and Y respectively. It can be seen that the overlap of pressure points is difficult, but since the ink layer is the area, not the point, and the amount of turbulence of the ink roller is also small, it is difficult to overlap the pressure of the ink layer, but the pressure zone of the ink layer intersects. It is easier. The intersection of the ink layers makes it easier to accumulate the forces in the intersecting areas. This also determines the unfixed form of the ghosts, because we do not know the inequality of the roller and the ink roller. The influence of the movement, how the region of force intersects. The cumulative number of forces. As the modern printer develops at a high speed, the rotation speed per unit time is very fast, so the cumulative number of force accumulation in the unit time is also very large. If the diameter of an ink roller is X, the diameter of the plate cylinder is 6X, and the printing speed of the printer is 10,000/hour, the ink roller is 60,000 rotations/hour. The increase in speed increases the number of intersections in the force zone in the unit time, which increases the cumulative number of times the force per unit time. The frequency accumulative force refers to the force in the force area in the unit time, and the cumulative force of the number of intersections. Because of the difference in the structure of the graphic and text, each print product is different in the frequency of its accumulation force. Because of the different printing speeds, the frequency of accumulation in the unit time is different. Also due to the different deformation patterns of the ink roller rubber, the accumulating frequency of frequency accumulation frequency is different. It can be said that the formation of ghosts requires the accumulation of accumulation power at the same frequency, but the actual situation is that it is not easy to keep the same frequency in the ink path. Therefore, the difference in frequency is also a factor that makes ghosts uncommon and has a short duration. Nowadays, the device for eliminating ghosting by various printer manufacturers is mainly designed from the perspective of changing the cumulative frequency of ink channels. For example, the device for removing ghosts from printers of Beiren is to change the frequency of accumulative force of the ink channel by changing the squeaking size of the ink roller. The device for eliminating ghosts of Roland presses is to change the axial position of the printing roller. To achieve the change in the frequency of the accumulation of the ink path, the two are compared to change the frequency source of the change of the position of the printing roller, and changing the size of the ink roller is to change the frequency transfer process, so the conclusion is drawn. It is more effective to suppress the formation of ghosts by changing the axial position of the platen roller. A little thought about the Roland printing press to eliminate ghost devices. The author has not operated such a machine, but knowing that Roland has such a device, he made the following conjecture based on his own knowledge: 1, by the position of the roller change the way. The way in which the axial position of the printing roller is changed is absolutely not the same as the axial shaking of the ink roller, and it is impossible to change the axial position continuously during the printing process because (1) If the axial position is continuously changed in the printing, violent friction will occur between the ink roll and the printing plate, which will make the printing plate resistant to printing and the ink roller wear increase. (2) Constantly changing the axial position can change the cumulative force, but since the cumulative force needs to be accumulated to a certain degree, it is only necessary to change the frequency before the cumulative force reaches the critical value. Therefore, it is necessary to constantly change the plate roller. The axial position is not necessary. As a result, it can be introduced that in this device, the axial position of the plate roller is discontinuously changed. 2. Where to change where the printer is running. The change of the axial position of the printing roller should be the movement of the printing roller to the neutral position of the plate cylinder, because if the axial position of the printing roller is changed in the printing part, the dot will be deformed to generate the ink bar. Ghosting and other printing problems. 3. Change the axial position of several reel rollers. There are generally four reed rollers. Since the axial position of the reversing roller must be discontinuous, it must be changed at the neutral position of the plate cylinder. Therefore, from the perspective of ease of motion control, only the first Based on the realization of roller The change of the axial position is easier. At the same time, the ink path is seen as a whole. Changing one of the plate rollers realizes the change of the overall frequency of the ink path. Therefore, it is concluded that this device has only the first printing roller. The axial position has changed. The exclusion of ghosts in the printing process, the most difficult to avoid and rule out is mechanical ghosting, and the most common type of mechanical ghosting is missing ghosts. It is more likely to occur when printing with clear inks, and rarely when using opaque inks. In cooperation with the printing process, some measures can be taken to reduce the lack of ghosting. Therefore, care should be taken to avoid designs that are prone to missing ink ghosts, such as large frames, large fields, and so on. If you must adopt such a design, you can take the following measures: (l) Use as much of the picture as possible in the design. Generally, there will be no ghosting phenomenon for the halftone printing that does not involve the field. (2) Change the design. Reducing the density of large borders or large fields, balancing the density gap between images on the screen and the field, and trying to balance the ink on the entire page to reduce the appearance of ghosts. For example, if two pictures are placed on the right side of a printed sheet, it is easy to produce ghosting when printing; if the design is changed so that two pictures are placed separately, one on the left and right, and the entire ink volume is used to balance, the ghost can be avoided. . (3) When layout, rational layout. The proper layout will ensure that the ink roller has enough ink time to avoid ghosting. For example, if a design is to place a large picture in the field, when the imposition is made, if the printer is large enough, it can be placed behind two pictures on a white background. (4) Use a color bar placed outside the graphic section to transfer excess ink from the ink roller. These color bars are called ink sticks. (5) Adjust the printing press and increase the amount of ink supplied by the missing ink fountain. In addition, some presses are equipped with inclined even ink roller, which can effectively solve the lack of ink ghosts, that is, use different parts of the ink roller to print different parts of a large area on the ground, so that the ink roller will not lack ink. (6) Rotate the design layout by 90°. In the case of printing large bold characters on the ground, for example, if the ink roller first inks large bold characters, and then inks the ink on the spot, printing one by one, it is easy to cause ghosting. However, if the print sheet is transposed by 90°, the part of the ink roller can be used to ink the font, and the other part can be inked on the spot, which can effectively avoid the lack of ink ghosting. Source: Printing Quality and Standardization