Analysis of the inking mechanism of sheet fed offs

An analysis of the inking mechanism of the sheet fed offset press the quality of the press is ultimately measured by the quality of the print. Printing ink color uniformity, no change in intensity, is the minimum quality requirements. However, due to the gradual progress of people's understanding, the inking mechanism of the printing machine is also constantly improving. In the process of offset printing, it is the key to control the ink balance, and controlling the movement of inking roller is a very important factor to improve the quality of printed matter, especially requiring the printer operator to accurately adjust it, but this is often ignored by many people, which is also a problem that the author often ignores when operating the printer in enterprises, and even affects the printing quality of exquisite printed matter

at present, the degree of automatic control of modern printing machines is getting higher and higher. The inking mechanism can be accurately adjusted according to different printing products: the adjustment of the amount of inking momentum and the position of the starting point, so as to better improve the product quality

next, let's talk about the structure of the inking mechanism, and work together to correctly use and operate the inking mechanism

I. function and composition of inking mechanism

inking mechanism can be roughly divided into three parts: inking roller, cooling mechanism of inking roller, and power driving mechanism of inking roller. The working part of inking mechanism is inking roller. The inking roller rotates in both circumferential direction and axial direction. The function of circumferential rotation is the same as that of other ink leveling rollers, which plays the role of circumferential ink leveling. The axial movement of inking roller not only requires fundamental transformation in the plastic granulator process, but also plays a major role in beating the ink evenly in the axial direction. Generally, the inking mechanism has three inking rollers: the upper inking roller will pull apart, thin and even the uneven ink layer supplied by the ink supply device; The intermediate ink roller is responsible for storing ink, homogenizing and distributing ink flow; The lower inking roller is responsible for beating up the uneven ink corresponding to the graphics and blank parts on the printing plate left on the roller after the inking roller inks the printing plate

second, the structure of inking roller

is different on different brands of printing machines, which is generally divided into two categories: integral inking roller and three section inking roller. The integral inking roller is simpler in manufacture than the three section inking roller, and its geometric accuracy and radial runout are easy to be guaranteed, but it is inconvenient to install and repair, so it must be installed and disassembled in a certain order. Gaobaoli Bida large format offset press uses an integral ink roller

III. temperature control device of inking roller

because the inking roller rotates in both circumferential direction and axial direction, the ink is subject to friction in these two aspects. After the printing machine runs, the ink temperature will soon rise to the normal working temperature of 20 ℃ ~ 30 ℃. If there is no temperature control device, the ink temperature will continue to rise, and the ink temperature of the printing machine working for a long time will rise to 70 ℃ or above, At this time, many characteristics of the ink will change greatly, and the printing quality will certainly not be controlled, so we can print high-quality prints only by ensuring the normal working temperature of the ink in the printing process. Modern printing machines are equipped with temperature control devices. The temperature control devices of inking rollers of printing machines manufactured in each country are different, but the principle is basically the same. They all use the method of circulating coolant in the center of inking rollers to reduce the temperature of inks

IV. adjustment of inking mechanism

the adjustment of inking mechanism has two aspects: the adjustment of inking roller momentum and the adjustment of inking starting point. The adjustment of these two aspects should be adjusted according to the specific situation of the print. Next, combined with the typical inking mechanism, we need to further explore the analysis of efficient blending means

1. Adjustment of inking roller's string momentum

the maximum string momentum of inking roller is different on different brand printing machines and printing machines with different formats. For example, the maximum string momentum of domestic J2108 and j2203 is 25mm, PW is 40mm, Heidelberg m-offset (48CM 65cm) is 30mm, Heidelberg CD102 is 35mm, and the maximum string momentum of gaobaoli Bida series printing machines is 70mm. The range we can adjust is 0 ~ maximum string momentum. All of the above inking mechanisms are the printing plate cylinder rotating twice, and the inking roller reciprocating once (except for Mitsubishi printing machine, the printing plate cylinder rotating three, and the inking roller reciprocating once). The reversing of the inking roller should be carried out when the roller is in neutral, otherwise the ink bar is easy to appear

how much string momentum is the best when printing? This depends on the specific situation of the printed matter: for most printed matter, the string momentum is generally not less than the distance between the two ink area screws, which is adjusted to half of the maximum string momentum in many times; For special prints, it is necessary to adjust to a specific string momentum. Here are two extreme examples of molding characteristics: suppose that the left side of the print in Figure 5 is a spot color solid block, and the other parts are blank, then we can adjust the string momentum to a very small value. At this time, if the string momentum is too large, it will destroy the local adjustment of the ink (this product is often encountered in the original work unit); If we print a print with almost the same ink volume of the whole format, then we can adjust the maximum ink volume and evenly mix the ink in the axial direction to the greatest extent, which can also make up for the inconsistent adjustment of the ink area. So how to adjust the string momentum? The power driving mechanism of inking roller of different printing machines is different, which should be adjusted according to the specific structure

2. Adjustment of the starting point of inking roller movement

the starting point of inking roller movement is the relative position between the inking roller and the printing plate cylinder when the inking roller starts to move. When this position changes, the ink layer thickness of the printed matter in the paper direction will also change accordingly. When adjusting Heidelberg m-offset, loosen the screw, jog the printer, the drum rotates, and the inking roller does not move, so the corresponding position changes, and the starting point of inking is also changed

kba105u inking roller starting point can be adjusted to any position according to the situation of the printed matter. When adjusting, you can directly adjust (setting of lateral distribution) on the console. By changing the adjustment number (value range-233 ~ 710) of the starting point of inking roller of each color deck, the corresponding starting point of inking roller is also changed. It can be adjusted according to the graphic information on each color plate