Analysis of the ink fountain mechanism of sheetfed offset printing machine

The quality of the printing press is ultimately measured by the quality of the printed product. The ink is uniform in color, with no shades of change, and is the minimum quality requirement. However, due to the gradual recognition of the level of people's understanding, the ink-sinking mechanism of printers is also constantly improving and constantly improving. In the offset printing process, controlling the ink-water balance is the key, and controlling the skew of the ink roller is a very important factor in improving the quality of the printed matter. In particular, the operator of the printing press needs to make precise adjustments, but this is often the case. It was ignored by many people. This is also a problem that the author usually ignores when the company operates the printing press, and even affects the printing quality of fine prints.

Nowadays, the degree of automatic control of modern printing presses is getting higher and higher, and the ink stringing mechanism can be precisely adjusted according to different printing products: the adjustment of the size of the string and the position of the starting point, so as to better improve the product quality.

Here we talk about the structure of the ink stringing mechanism and use and operate the ink stringing mechanism correctly.

First, the role and composition of the ink stringing mechanism

The ink stringing mechanism can be roughly divided into three parts: the ink stringing roller, the cooling mechanism of the ink stringing roller, and the power driving mechanism of the ink stringing roller. The working part of the ink stringing mechanism is a tandem roller. The ink roller has both circumferential rotation and axial rotation. The effect of the rotation in the circumferential direction is the same as that of other uniform rollers, which plays a role in circumferentially evening the ink. The main effect of the axial vortexing of the ink stringer is to evenly ink the ink in the axial direction. The general ink distribution mechanism has three ink strings: the ink string on the ink string pulls, thins, and evens the uneven ink layer supplied by the ink supply device; the intermediate ink roller bears ink storage, smoothing, and distributing the ink flow. The role of; under the string of ink roller is responsible for even after the ink roller to the printing plate after the ink remaining on the roller and the printing plate on the text and blank parts corresponding to the uneven ink.

Second, the structure of the ink roller

Different brands of presses are not the same, are generally divided into two categories: the whole string of ink rollers and three string ink roller. The integral ink fountain roller is simpler to manufacture than the three-section ink fountain roller—the geometric accuracy and radial runout are easily guaranteed, but the installation and repair are inconvenient, and must be installed and disassembled in a certain order. The KBA Rapida large format offset press uses an integral ink fountain roller.

Third, the ink roller temperature control device

Since the ink string roller has both circumferential rotation and axial rotation, the ink is subject to friction in these two aspects. After the printing machine runs, the temperature of the ink will quickly rise to the normal working temperature of 20°C to 30°C. If there is no temperature control device, the temperature of the ink will continue to rise and the temperature of the ink for the long time of the printing press will rise to 70°C or more. At this time, many characteristics of the ink will change greatly, and the printing quality will certainly not be obtained. Control, so we only guarantee the normal operating temperature of the ink in the printing process in order to print high-quality prints. Modern printing presses are equipped with temperature control devices. The temperature control devices of the ink rollers in each country's printing presses are not the same, but the principles are basically the same. They are used to reduce the string by circulating the coolant through the center of the ink roller. The temperature of the ink roller to reduce the temperature of the ink.

IV. Adjustment of ink string mechanism

There are two aspects of the adjustment of the ink string mechanism: the adjustment of the skewer ink string amount, and the adjustment of the ink string ink ink string starting point. These two aspects of adjustment are to be adjusted according to the specific circumstances of the printed product, the following will be a specific analysis of the typical string ink mechanism.

1. Adjustment of skewer roller momentum

The maximum amount of stringer rotation is not the same for different brands of presses and presses with different formats. For example, the maximum string of domestic J2108 and J2203 is 25mm, 40mm for PW2920-1, and M-OFFSET (48cm x 65cm) for Heidelberg. 30mm, Heidelberg CD102 is 35mm, KBA Rapide 130-162a series printers have a maximum string of 70mm, we can adjust the range of 0 ~ maximum string. The above-mentioned several ink-chaining mechanisms are each a series of rotations of the printing plate cylinder and two-rotating series of ink rollers (except for the Mitsubishi printing machine, and the printing plate rotating three-rotating series of ink rollers is rotated and reciprocated once). The commutation of the ink roller should be carried out when the roller is in the neutral position. Otherwise, the ink stick will easily appear.

What is the best amount of momentum when printing? This depends on the specific circumstances of the printed matter: For most prints, the amount of stringing is generally not less than the spacing of the two ink-zone screws, and in many cases it is adjusted to half of the maximum amount of play; for special prints, it must be adjusted to a specific The amount of stringing, here are two extreme examples: Assume that the left side of the printed matter in Figure 5 is a spot color block on the left, and the other part is blank. At this time, we can adjust the string momentum to a very small value. Large words will destroy the local adjustment of the ink (this kind of product is often encountered in the original workplace); and if printing a whole frame of ink requires almost the same amount of printing, we can adjust the maximum amount of ink, and the maximum Abrasion ink in the axial direction, which can also make up for inconsistencies in the adjustment of the ink zone. How to adjust the amount of string? The power mechanism of the different rollers of the different printing machines is not the same, which is adjusted according to the specific structure.

2. Adjustment of the starting point of the stringer

The starting point of the vortexing roller is the relative position of the serigraph roller when it starts to oscillate. When this position is changed, the ink layer thickness of the printed matter in the feeding direction must also change accordingly. For the M-OFFSET adjustment at Hoi Bo Castle, loosen the screw, press the printer, the drum rotates, and the ink roller does not move, so the corresponding position changes and the starting point of the ink string is changed.

The adjustment of the starting point of the ink roller in KBA105U can adjust the starting point of the ink roller to any position according to the condition of the print. Adjustment can be performed directly at the console (Setting of lateral distribution). By changing the starting point of the ink fountain roller for each color group (Value range-233 to 710), the corresponding starting point of the ink fountain roller is also changed. . Can be adjusted according to the graphic information on each color version.