The quality of the printing press is ultimately measured by the quality of the printed matter. The ink color of the printed product is uniform and there is no change in density, which is the minimum quality requirement. However, due to the gradual understanding of the level of people, the printing machine ink-crossing mechanism is also constantly improving and improving. In the offset printing process, the control of water and ink balance is the key, and the control of the inking of the ink roller is a very important factor to improve the quality of printing, especially the printer operator needs to accurately adjust it, but this is often Neglected by many people, this is also a problem that the author often ignores when operating a printing press in an enterprise, which even affects the printing quality of fine prints.
Nowadays, the automatic control of modern printing machines is getting higher and higher, and the ink-crossing mechanism can be precisely adjusted according to different printed products: the adjustment of the magnitude of the cross-motion and the position of the starting point, in order to better improve the product quality.
Next, we will talk about the structure of the ink inking mechanism, together to correctly use and operate the ink inking mechanism.
1. The function and composition of the ink inking mechanism
The ink inking mechanism can be roughly divided into three parts: ink inking roller, cooling mechanism of ink inking roller, and power driving mechanism of ink inking roller. The working part of the ink inking mechanism is the ink inking roller. The inking roller has both circumferential rotation and axial tandem motion. The function of the rotation in the circumferential direction is the same as that of the other ink leveling rollers, and plays the role of equating the ink in the circumferential direction. The main function of the axial tandem of the tandem roller is to evenly distribute the ink in the axial direction. Generally, the ink inking mechanism has three ink inking rollers: the upper ink inking roller pulls apart, thins and smoothes the uneven ink layer supplied by the ink supply device; the middle ink inking roller is responsible for ink storage, smoothing and distribution Function; the lower ink roller is responsible for smoothing the uneven ink remaining on the roller after inking the ink roller to the printing plate and corresponding to the graphic and blank portions on the printing plate.
Second, the structure of the ink roller
It is different on the printing machines of different brands, and is generally divided into two categories: overall ink inking rollers and three-section ink inking rollers. The overall inking roller is simpler to manufacture than the three-section inking roller—geometric accuracy and radial run-out are easily guaranteed, but installation and repair are more inconvenient, and the assembly and disassembly must follow a certain order. KBA Rapida large-format offset presses use an integral cross-ink roller.
3. Temperature control device of ink roller
Because the ink roller has both circumferential rotation and axial movement, the ink is subject to friction in these two aspects. After the printing press is running, the temperature of the ink will soon rise to the normal working temperature of 20 ℃ ~ 30 ℃. If there is no temperature control device, the temperature of the ink will continue to rise, and the temperature of the ink will rise to 70 ℃ or above for a long time of the printing press. At this time, many characteristics of the ink will change greatly, and the printing quality will definitely not be obtained Control, so we can only print high-quality prints when we guarantee the normal working temperature of the ink. Modern printing presses are equipped with temperature control devices. The temperature control devices of the inking rollers of the printing presses made in each country are not the same, but the principle is basically the same. The method of circulating the coolant through the center of the inking rollers is used to reduce the string. Ink roller temperature to lower the ink temperature.
4. Adjustment of the ink-crossing mechanism
There are two aspects to the adjustment of the ink inking mechanism: the adjustment of the inking of the ink inking roller and the adjustment of the starting point of the ink inking of the ink inking roller. The adjustment of these two aspects should be adjusted accordingly according to the specific conditions of the printed product. The following is a detailed analysis in conjunction with the typical ink-crossing mechanism.
1. Adjustment of tandem roller tandem momentum
The maximum tandem of the inking rollers is different on different brands of printing machines and printing machines of different formats. For example, the maximum tandem of domestic J2108 and J2203 is 25mm, PW2920-1 is 40mm, Heidelberg M-OFFSET (48cm × 65cm) 30mm, Heidelberg CD102 is 35mm, KBA Rapida 130-162a series printer's maximum series movement is 70mm, the range we can adjust is 0 ~ the maximum series movement. The above-mentioned several ink-crossing mechanisms are all the reciprocating series of the plate cylinder rotating two-revolving series ink rollers (except for the Mitsubishi printing machine, the plate cylinder rotating the three-revolving series ink roller reciprocating series). The reversal of the ink roller should be carried out when the roller is in neutral, otherwise ink sticks are easy to appear.
So what is the best series momentum when printing? This depends on the specific situation of the printed matter: for most printed matters, the crosstalk is generally not less than the distance between the two ink zone screws, and in many cases it is adjusted to half of the maximum crosstalk; for special prints, it must be adjusted to a specific For the series momentum, here are two extreme examples: assuming that the left side of the printed matter in Figure 5 is a solid spot of solid color, and the other parts are blank, then we can adjust the series momentum to a very small amount. If it is large, it will destroy the local adjustment of the ink (this product is often encountered in the original work unit); and if printing an entire volume of ink almost requires a consistent print, then we can adjust the maximum ink volume, the maximum degree The ink is evenly distributed in the axial direction, which can also compensate for the inconsistency of the adjustment of the ink area. So how to adjust the series momentum? The power drive mechanism of the ink rollers of different printing machines is not the same, which should be adjusted according to the specific structure.
2. Adjustment of the starting point of tandem roller tandem motion
The starting point of the tandem roller tandem is the relative position of the tandem roller and the plate cylinder when it starts to tandem. When this position changes, the thickness of the ink layer of the printed product in the direction of the paper should also change accordingly. For the mariner? -OFFSET adjustment, loosen the screw, jog the printing machine, the cylinder rotates, and the ink roller does not move, so the corresponding position has changed, and the starting point of the ink string has been changed.
In KBA105U, the adjustment of the starting point of the inking roller can be adjusted to any position according to the condition of the printed matter. During the adjustment, it can be adjusted directly on the console (Setting of lateral distribution). By changing the starting point of the inking roller of each color group to adjust the number (Value range-233 ～ 710), the starting point of the corresponding inking roller has been changed. . It can be adjusted separately according to the graphic information on each color version.
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