Currently, chromatography error printing machine generally comprises circumferential (vertical), axial (transverse) direction and a diagonal (skew) error of three directions. For fast on the version, save preparation time, two-color and multi-color offset printing machine plate cylinder are designed registration agency. For circumferential and axial errors, the registration mechanism can be easily solved, but when the printed product produces an error at a certain angle, as shown in Figure 1, it is difficult to accurately use only the circumferential and axial registration mechanisms. Adjusted. If the error is neglected, the quality of the printed matter will be greatly reduced, and the customer's requirements cannot be met. If the error is handled, the method of reinstalling the printing plate can only be used to solve the problem, which is time consuming and laborious, and because of the accuracy. The difference in experience of the operator can make a big difference. Therefore, the registration of the diagonal direction is important for ensuring the quality of printed matter in multi-color printing.
At present, in the printing production, the registration method in the diagonal direction is mainly divided into three types: directly pulling the printing plate, shifting the plate cylinder, and changing the paper position.
(1) Pull the plate directly
Some printing presses (such as Akiyama Jprint4p440) use the method of directly pulling the printing plate to achieve automatic registration in the diagonal direction, that is, changing the relative position of the printing plate and the plate cylinder, so that the graphic of the printing plate on the drum can be correctly Transfer to paper. The adjustment of the diagonal direction by the plate plate has the advantage that the oblique adjustment distance is large, the adjustment range is up to ±2 mm, and the operation is relatively simple. However, the printing plate is also greatly damaged, the printing plate printing durability will be greatly reduced, and the machine cost and printing cost will be greatly increased.
(2) Displacement plate cylinder
The Heidelberg printing press often uses a displacement plate cylinder to adjust the plate cylinder by adjusting the eccentric sleeve to achieve diagonal registration. The principle is to install the servo motor and transmission mechanism at one end (operation surface) of the plate cylinder, and the other end. Fixed (transmission surface), the motor drives the eccentric sleeve to push the plate cylinder to produce lateral displacement in front of or behind the operating surface, thereby changing its relative position with the center line of the blanket cylinder, so that the printing plate and the blanket axial point The circumferential relative displacements are unequal to achieve registration in the diagonal direction. The register mechanism refers to the principle of the circumferential direction and the axial register mechanism, and realizes the movement of the plate cylinder by using the rotating eccentric sleeve, and the principle is clear and the structure is simple. It is a relatively mature control system that is easy to implement and has become the main method for diagonal adjustment of most offset presses. According to the adjustment principle of the displacement plate cylinder, the center line of both the plate cylinder and the blanket cylinder after adjustment is no longer parallel, and the plate cylinder and the inking roller are also relatively displaced. The bearing and the gear of the plate cylinder drive side are The secondary is unfavorable, and there are two problems: the pressure between the plate cylinder and the blanket cylinder will change; the pressure between the plate cylinder and the inking roller and the water roller will also change. Therefore, a set of follow-up pressure regulating mechanism can be designed to form a linkage effect to solve this problem.
(3) Change the position of the sheet
In solving the diagonal registration error between multiple colors, the principle of the first two methods is to use paper as the reference standard to adjust the relative position of the printing plate and paper. In the same way, we can imagine using the graphic of the printing plate as a reference to change the relative position of the paper to achieve the purpose of diagonal registration. It can be adjusted by adjusting the position of the rule or changing the amount of paper creping on the transfer cylinder. Adjusting the position of the rule, the position of the paper between the various units will change, which obviously does not apply to the case where only one color is not printed and the other color groups are accurate when printing. As with the principle of the displacement plate cylinder, a driving motor is driven on the operating side of the paper conveying roller to drive the screw mechanism, and the eccentric sleeve is pushed to move the paper conveying roller so that the center line is inclined at an angle to the center line of the adjacent roller, so that The bite paper will change at the bite position, causing the paper to deflect during the transfer process and complete the registration of the diagonal direction. This adjustment method belongs to a new type of diagonal registration method, which is widely used in foreign offset printing machines, which can effectively solve the overprinting problem of color groups without affecting the overprinting of other color groups, and can also save the mobile printing plate. The step of the roller reduces the waste of the overprint paper and overcomes the problem of pressure change between the printing plate and the water roller and the ink roller due to the deflection of the plate cylinder.
Overprinting accuracy is an important indicator for measuring the performance of printing presses and verifying the quality of printed matter. Because there is no mature system in China, the research and development of diagonal direction registering agencies has a long way to go.
The above content is selected from Keyin Media. Printing Technology ·Digital Graphic Arts , No. 4, 2012, please pay attention to the journal channel for more journal content . Click on the latest journal content to enter the electronic journal channel of Keyin.com.
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