Flow printing method of the most popular offset pr

2022-08-04
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"Flow process" printing method of offset press before the early 1990s, the popularity of multi-color offset press was still relatively low, and most of the printing equipment used by many printing plants were domestic monochrome Offset Press and two-color offset press. For the printing of large quantities and tight construction period, some manufacturers often adopt the "flow process" printing production method of two or more offset presses to complete. For example, four-color printing mostly adopts two two-color offset printing machines "flow process", sometimes it also adopts the combination of one two-color offset printing machine plus two or one monochrome Offset printing machine; Five color printing generally adopts the combination of two two-color offset printing machines and one monochrome Offset printing platform machine such as Jin min. Of course, there are many other combinations

in recent years, with the popularity of four-color and multi-color offset printing machines, such a "flow process" printing method is not often used. However, these methods and experiences may be helpful to some printing plants, so I will briefly introduce the practices of the author's unit in that year for your reference

selection of printing equipment for "flow operation"

according to the specific conditions of the printing equipment of our factory (most offset printing machines are produced by "beiren"), all offset printing machines that participate in "flow operation" in our factory, whether two-color or monochrome, are produced by "beiren" (the two-color machine is "03" and "05", and the monochrome machine is "08"). This is mainly because the relevant parameters of the impression cylinder, blanket cylinder and plate cylinder of the three offset printing machines produced by "beiren" are exactly the same. Only in this way can we maximize the consistency of the "imprint" length of two or more offset printing machines, that is, the consistency of the "imprint lengthening" or "imprint shortening" (of course, on the basis of reasonable lining). In addition, it is understood that the front and side rules of the three offset printing machines are exactly the same, which can ensure the positioning consistency of the paper on the machine for two or more times, thus facilitating accurate overprint

adjustment of offset press

"two machine flow operation" or "multi machine flow operation" need to focus on solving the problem of mutual overprint between machines. Once the printing press is selected, the adjustment of two or more offset presses in the same "assembly line" before printing is very important. Our approach is:

technicians in the workshop are responsible for leading all the receiving machines of the relevant machines (if two two-color offset printing machines are produced according to the two shift system, there are four receiving machines in total) to uniformly adjust the relevant offset printing machines, so that each receiving machine can fully understand and grasp the situation of other machines, so as to be well aware of them, which is more conducive to the reasonable connection between the front and rear machines and the two shifts of the same machine. After adjustment, the operator is not allowed to adjust each machine without authorization. If adjustment is necessary due to problems in the work, the operator can only make corresponding adjustment under the direct guidance of the workshop technicians, fully understand the specific conditions of the modern enterprise management system and printing parts implemented by the relevant machine companies, combined with the production process formulated in advance, and after comprehensive consideration, and timely communicate with the lead machine of other relevant machines. The specific adjustment methods are as follows:

1 Pressure adjustment

first, determine the printing pressure of each machine according to the production process, and comprehensively consider a series of conditions such as the thickness, surface smoothness and ink area (in most cases, keep the same pressure). Never allow the machines to "fight their own battles", which leads to the phenomenon that the pressure on the machine at the printing point is too light, but the pressure on the machine at the printing site is blindly increased

after the pressure between the embossing cylinder and the blanket cylinder and the pressure between the blanket cylinder and the printing plate cylinder are determined, carefully adjust the center distance of the 3 cylinders, and accurately lining the printing plate cylinder and the blanket cylinder, The blanket cylinder and the printing plate cylinder of each machine must have the same lining thickness and lining material (except that some prints intentionally thicken the first color printing plate cylinder lining to overcome the phenomenon of paper pumping). The purpose of this is to ensure that the "imprint" printed by each offset press is the same size as the original. Only in this way can we ensure that the mutual overprint between the machines is accurate. At that time, many manufacturers popular a doggerel: "the imprint is as big as the original, and we are not afraid of overprinting with anyone", which shows that we all recognize the importance of the change in the length of the "imprint" to overprinting

in order to ensure that "the print is as big as the original", we have made a lot of efforts. In addition to the strict adjustment of the machine, in order to facilitate inspection, the size of the original plate is also recorded on the film during plate making. In this way, the difference between the "imprint" and the actual size of the original can be accurately known in the process of printing and printing, so as to facilitate timely and accurate adjustment

2. Regulation of rules

we all know that the accuracy of the front and side rules is the key to affecting the overprint accuracy. For "two or more machines flow process", regulation of rules is even more important, without any carelessness or carelessness

first, on the basis of keeping the two front gauges parallel to the axis of the embossing cylinder, adjust the size of the jaws of all relevant machines (the amount of paper in the teeth of the embossing cylinder) to be consistent, and the height of the front gauge from the paper feeding table should also be accurate and consistent. The side gauge stop board must be adjusted to a position perpendicular to the front gauge, and the position of the side gauge of the relevant printing machine on the side gauge axis (incoming and outgoing position) and the paper pulling force, time and distance must be adjusted to make them consistent. In addition, carefully adjust the flatness of the paper feeding table, the position and tightness of the paper feeding line belt, and the pressure and position of the paper pressing wheel and brush wheel. We believe that only in this way can we ensure that each positioning of the paper is both accurate and consistent, and only the paper feeding table with the same flatness can ensure that the paper enters the "embossing area" in the same state, thus creating favorable conditions for overprint and largely avoiding the disadvantage of "dumping the claim of the plastic ocean foundation headquartered in the United States"

it should be pointed out that once the position of the front gauge and the side gauge is determined, no matter which offset press is allowed to adjust, especially for the front gauge, it is not allowed to adjust. Only when the paper cutting precision is very high, can the side gauge be slightly adjusted, but it must be approved by the workshop Technician in charge and commanded by him on site, and must be fully communicated with other leaders. The method of "finding the rules" by "pulling the plate" can only be adopted when installing the plate, and the method of "finding the plate" by adjusting the rules must not be used to make the printing accurate. This seems to be a bit troublesome, but it is also necessary to ensure that overprint is worth it

3. Adjustment of paper gripper teeth

the adjustment of paper gripper teeth includes the adjustment of the tooth pads and paper gripper teeth of the three parts of the imprint cylinder, paper delivery tooth and paper receiving tooth row. Only accurate adjustment can ensure the accuracy of overprint and avoid the occurrence of "angle swing" fault

the adjustment principle of paper gripper is to ensure the accuracy and flatness of all tooth pads, as well as the consistency of paper gripper force, friction coefficient, opening and closing action, etc. The specific adjustment methods are introduced in many relevant materials and books and will not be repeated here

in addition, in order to improve the overprint accuracy, a series of measures should be taken, such as the paper cutting size must be accurate and maintain a 90 ° angle, all offset printing machines should use the same printing speed, and the temperature and humidity of the workshop should be strictly controlled

although the "flow process" is difficult, as long as the methods are appropriate and the measures are effective, high-quality prints can be printed, and the production efficiency can be greatly improved. (end)

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