Positioning of printing plate front gauge

For a printing plate worker, the positioning of the plate front gauge is the first step in making the plate. It is the positioning of this dimension. It is not a fixed data, but an uncertain data that changes from time to time due to changes in conditions and goals. It should start with three aspects. The specific analysis is as follows:

First, we must master the offset press model, manufacturer and other characteristics

Each offset press of each printing unit has different characteristics due to its model, manufacturer, etc., so the characteristics required for their operation are also different. Not to mention the difference in the positioning of the front gauge of each offset press. Here are some typical offset presses for this unit as an example to explain the difference in the positioning of their front gauges. Such as: Beijing People's Machine Factory Offset offset press, like the J2108B type monochrome off-set offset printing press it uses the printing plate front gauge size positioning is 9cm, which is generally speaking the version of the heart to the plate edge distance It is 9cm; like the JS2102 monochrome split double-sided offset printing machine, the positioning of the front and back dimensions of the upper and lower printing plates it uses is the same as 4.5cm, that is, the distance from the printing plate to the printing plate edge is 4.5cm; The same as the double-sided split monochrome offset press, the upper and lower printing plates used by it have different dimensions of the front gauge, the front gauge size of the upper plate is 7.5cm, and the front plate size of the lower plate is 6cm. Therefore, it is said that the positioning of the front gauge of the printing plate used in the off-color monochrome double-sided offset printing press will be different due to different manufacturers; the J2205 off-color two-color offset printing press produced by the Beijing People's Machinery Factory will also be applied. Different models, the plate used by the former size of the gauge is not the same, its front gauge size positioning is 10cm, but in the printing of books and magazines, the size of its front gauge is 10cm, and when the book cover is reprinted, it's The positioning of the front gauge is 9cm, which is another feature.

Second, the exact understanding of the work requirements and the use of the plate to be used

Usually printing companies, their business has a certain degree of regulation, which is often said that within a certain range, there will rarely be cross-professional to undertake business. For the plate-making staff, there is an unwritten rule among them: In the non-special case, the orientation of the pre-regular dimensions of the plates they make seems to be fixed. However, in special circumstances, we must first look at the subpoenas and samples to find countermeasures. The following uses the printing plate of the book cover as an example to explain the positioning of its front gauge in the actual operation process. It is mainly divided into five steps:

1 After receiving the subpena, first of all, it is necessary to clearly read the requirements written above (the requirements of the printing plate), and then clearly arrange the ink pad. 2. Distinguish the sky and earth angles of the supply film, that is, the direction of the mouth. The actual size of the printing plate is good and whether there is a cut. 3. Whether or not the cover of the print is required to leave a mouthful, special circumstances should be treated specially. 4. To see where the lines of the film are, it should be noted that the actual size of the front gauge is the normal size plus the size of the slot minus the size of the machine's nip (generally the gap size of the offset machine is between 1.5 and 2 cm). 5. Finally re-measure the size of the entire version of the heart, and the contrast with the paper used. From this we can also see that if we want to make a qualified plate, the size of the front plate of the printing plate is just right, and we must see clearly what the target is.

Third, the specific situation of raw materials

The printing plates often only allow people to remember how to calculate the size of the front gauge, and ignore the specific conditions of the raw materials, because sometimes the specific conditions of raw materials, the positioning of the front plate of the printing plate has a decisive position. Such as: the size of raw materials. For example, the size of YP-II positive PS plate (92×76cm) used in the printing plate, the open cut paper size used for printing (normal folio size is 78.7×54.5cm, large folio The size is 85×58.5cm; the size of the international version of the folio is 88.5×61.5cm.) For example, the double-sided monochrome offset press produced by Harbin Machinery Factory has a size of 88x76cm, which is better than normal YP-II. The size of the printing plate of the positive type PS plate type is shorter by 4 cm, and the size of the three open papers (52×54 cm) and the long three open papers (36×78.7 cm), for example, are not so easily confusable. If you do not understand the facts, you will often make mistakes. Knowing the size of the paper used. If the plate is not held correctly by the size of the front plate of the plate during plate making, then the known size of the plate can be subtracted from the known plate size divided by 2 to obtain the size of the mouthpiece. Then, combined with the data of the usual plate making, this can calculate the size of the front gauge required by the offset printing machine for this printing plate. Because in the daily work, the gap between each offset press is generally in the range of 1.5 to 2 cm. According to the comparison between the two, the data obtained from the proof can be obtained.

In daily work, plate making is generally determined by the dimensions of the entire gauge. However, under special circumstances, the printing plate cannot be separated from the middle during production, or left or right in a certain direction. For example, the rubber roller on the offset printing press or a certain part of the plate cylinder may cause problems and the printing quality cannot be guaranteed. However, the remaining parts are very good. In order to minimize the damage, and without affecting the quality of the prints, it is necessary to move the entire version of the printing plate to the left or right while making the plate. Sometimes, In order to take care of the offset printing machine, it is not necessary to mobilize the paper-moving rules, so as to facilitate printing. In addition, the paper-cutting machine can calculate the paper without scraps, resulting in unnecessary waste. The 8-inch version of the printing plate will be produced in the 8-inch direction. Or right to one side.

For example, when the printing side opened the print, its opening specification was 52×54 cm. When this type of printed matter is printed, it is necessary to revive the paper-feeding rule line of the offset printing machine; if the size of the paper is opened to a normal half size at this time, the unused portion is cut off after printing. It will not cause waste of paper, and it will also save a lot of trouble for the operators on the offset press. What do you want to do? All of these require the plate-making staff to look carefully at the subpena before making the printing plate or to know that they are ready for printing. Paper. Otherwise, according to the conventional system of printing plates, it will certainly cause a waste of printing plates or paper.

: Guangzhou Printing