Offset press technology status, product function and market application introduction (serial 2)

This article was provided by Mr. Zhang Jianfa, Product Sales Director of Mann Rollland Beijing Representative Office. 1. The structural paper feeding section of the offset printing press is a part of the manual participation in traditional sheetfed offset printing presses, but the modern offset printing press is in high-speed multi-color printing. Under the circumstances, there are higher requirements for the accuracy and smoothness of paper feeding and automation. In order to make the paper transport smooth and accurate, the pendulum-type delivery mechanism and the front gauge are designed to be mainstream, and the manufacturers' side pull gauges and the feed speed change mechanism (to ensure that the high-speed running paper arrives at the front gauge has an instantaneous speed of zero) Differently, Roland offset presses are known for vacuum paper feeders, variable speed suction belts and pneumatic side pull gauges; they accurately control the left and right side of the paper stack and the front and rear of the paper feeder with position switches, which are double and printed with paper. Misplacement is particularly important. In the preparation of prepress operations, by inputting the paper thickness and other data into the console, the precise and rapid pre-adjustment of the paper feeder, front gauge, side gauge, dust-powder device and printing pressure can be automatically and accurately performed, thereby reducing the exact stop time. , improve production efficiency. At present, the paper size pre-adjustment function is the basic configuration of a modern sheet-fed multi-color offset press. The printing section is the heart of the printing press. After years of practice and theoretical discussion, the printing section has three rollers that are arranged at “seven o'clock”. The structure of double-diameter impression roller and transfer roller is already the mainstream of multi-color offset printing presses. The double-diameter transfer cylinder of the impression cylinder is a "five o'clock" arrangement, such as the traditional four-boot series of several large manufacturers. The advantages of using double-diameter impression cylinders are well known: First, the number of paper transfers between multi-color units is reduced, and the paper transfer error is greatly reduced; second, the paper red finishes printing during the impression cylinder pick-up. , And then to the transfer roller, so as to avoid overprinting caused by the paper is still printing errors; Third, due to the large curvature of the roller, the surface is smooth, embossing can reduce the dot transfer deformation. In addition, when the offset printing machine wears and wears for a certain number of years, this arrangement will not cause the phenomenon of printing on the paper regardless of the thickness of the paper when printing at the maximum paper width. For the combination of multi-color machines, the “in-line” printing method with overturning in several major printing presses in Germany has the features of low center of gravity, good rigidity, and top-down characteristics of the ink path. This ensures the printing quality and stability. It is beneficial, but each has its own solution to problems such as blemishes, tears, front and back registering, and double gargles brought about by flipping. Japanese manufacturers have introduced double-sided printing with double-sided printing for single-sheet double-layer multi-color offset printing presses. Since the ink path of the color group is bottom-up, it will have an impact on the quality of printed products, and it is inconvenient to maintain. Small is its advantage. The ink supply system is the key to ensure ink balance and prevent some common printing failures. At present, two or three plants, including Mann Rolland, have adopted a fast-response ink system. They feature a small number of ink rollers (less than 16), a small diameter roller, good heat dissipation, and high-speed printing. The ink roller is circulated and cooled only during offset printing and UV printing. In addition, in the printing of prints with different contents, such as Damoji's packaged printing products and lined with small ink-colored single commercial products, it is very important to discharge the ink at various speeds at a uniform speed. Only in this way can the consistency of the supplied ink viscosity be guaranteed. For this reason, Roland offset press has a variety of programs 1:3:6:9:18 for the initial setting on the ink supply cycle to ensure the stability of the print quality. Second, on the automation and auxiliary functions In order to improve the degree of automation of sheetfed multicolor offset press, improve the printing quality, reduce labor, all manufacturers have adopted similar pre-setting and management control system, not much to repeat here. Only talk about "dynamic automatic register" and "print quality inspection control method". The dynamic auto-registration and registration system has been applied to some manufacturers' sheetfed offset presses, but it is not as important as the web press to adjust the counterprinting devices by tension. Therefore, this system is on a sheet-fed offset press. The application effect is yet to be verified in practice. Up to now, Roland still insists on checking and controlling the printing quality and its process based on the density of printed inks, but does not follow the industry's monitoring and control methods of switching to spectroscopy. The reason is that the current print products are two-dimensional graphics, with a number of mature monitoring and control bar, such as Luna print control signal to achieve the detection of print quality, and spectrophotometric detection is based on the spectral 3-dimensional detection, It is not very practical for today's print products. The auxiliary functions such as light, drying and dusting are similar to each other. The polishing mechanism mainly includes two-roll coating and cavity blade coating. The former can quickly respond to changes in the coating amount of the coating solution. It is not economical; the latter, due to the use of ceramic anilox rollers, can very precisely control the coating thickness of the glazing solution on the entire sheet, and the glazing effect is simple and economical, making it suitable for various applications. There are IR, UV and hot air drying methods, which must be selected according to the actual application. As to whether the spraying is single-sided spraying or double spraying, the actual application area is not very large.