For a plate-making staff, the positioning of the size of the front plate is the first step in making a plate. This is the positioning of this size. It is not a fixed data, but an uncertain data that changes anytime and anywhere due to changes in conditions and goals. It should be started from three aspects. The specific analysis is as follows:
First, we must master the characteristics of the offset press model, manufacturer, etc.
Each offset press of each printing unit has different characteristics due to its model, manufacturer, etc., so the characteristics required for their work are also different. Not to mention that there is a difference in the positioning of the front gauge of each offset press. Let's take a few typical offset presses of this unit as an example to talk about the positioning difference of their front gauge size. Such as: Folio offset press produced by Beijing People's Machinery Factory, like J2108B type monochrome offset offset press, the positioning of the front plate size of the plate used is 9cm, which is the distance between the plate center and the edge of the plate It is 9cm; like the JS2102 type monochrome offset double-sided offset press, the positioning of the front and bottom plates used in it is the same as the 4.5cm, that is, the distance from the plate center to the edge of the plate is 4.5cm; but The same is a double-sided folio monochrome offset press, the positioning of the front gauge size of the upper and lower printing plates it uses is different, the positioning of the front gauge size of the upper version is 7.5cm, and the positioning of the front gauge size of the lower version is 6cm. Therefore, it is said that the positioning of the front size of the printing plate used for the two-sided monochrome double-sided offset printing machine will vary depending on the manufacturer; like the J2205 two-sided two-color offset printing machine produced by Beijing People's Machinery Factory, it will also respond. Depending on the model, the front gauge size of the printing plate used is also different. Its front gauge size positioning is 10cm, but when printing the book version, its front gauge size positioning is 10cm, and when changing the cover of the book, its The positioning of the front gauge size is 9cm, which is another feature.
2. Know exactly the job requirements and the users of the printed plates
Usually printing companies, their business has a certain standard, that is, it is often said that within a certain range, there will rarely be cross-professional undertaking business. For the plate-making personnel, an unwritten rule was formed among them invisibly: under non-special circumstances, the positioning of the pre-regulation size of the printing plate produced by it seemed to be fixed. However, if you encounter special circumstances, you must look at the summons and samples before looking for countermeasures. The following takes the printing plate of the book cover as an example to talk about the positioning of the front size in the actual operation process, which is mainly divided into five steps: 1. After receiving the subpoena, first of all, you must see the requirements written above (for printing Version requirements), and then arrange the stamp pad clearly. 2. Distinguish the angle of the sky and the ground supplied to the film, that is, the direction of the mouth. Measure the actual size of the version center and whether there is a cut. 3. Whether the printed cover is required to be relegated, special circumstances should be treated specially. 4. To see where the line of the film is, it should be noted that the actual data of the front gauge size is the normal size plus the size of the mouth minus the size of the machine bite (generally the bite size of the offset press is between 1.5 ~ 2cm ). 5. Finally, re-measure the size of the entire core and the comparison with the paper used. It can also be seen from this that if you want to make a qualified printing plate, the size of the front gauge of the printing plate is positioned properly, and it is inseparable from the requirements and the target.
3. The specific situation of raw materials
When making a printing plate, people often only remember how to calculate the size of the pre-regulation, and ignore the specific conditions of the raw materials, because sometimes the specific conditions of the raw materials have a decisive position in the positioning of the pre-regulation size of the printing plate. Such as: the size of raw materials. For example, the size of the YP-II type positive figure PS plate used in the printing plate (92x76cm), the size of the cut paper used for printing (the size of the normal folio is 78.7x54.5cm, the size of the large folio is 85x58.5cm; the size of the international folio is 88.5x61.5cm) such as the double-sided monochrome folio offset press produced by Harbin Machinery Factory, the size of the printing plate used is 88x76cm, which is more than the normal YP-â…¡ type positive picture The size of the printing plate made by PS is 4cm shorter. For example, the size of the square three-sided paper (52x54cm) and the long three-sided paper (36x78.7cm), the size difference between them is not obvious and easy to confuse. If you don't understand the truth, you will often make mistakes. Know the size of the paper used. If the front size of the printing plate is not correct when making a plate, then the size of the cut-out paper can be obtained by subtracting the size of the known plate center divided by 2 to get the size of the bite. , And then combined with the usual plate-making data to calculate, so that you can calculate the size of the front gauge required by this printing plate for the offset press. Because the bite of each offset press is generally in the range of 1.5 ~ 2cm in daily work, according to the comparison between the two, you can get whether the verified data is correct.
In daily work, in general, the plate-making size is the front gauge size to determine the entire plate heart distance. However, under special circumstances, the printing plate can not be offset from the middle or left or right in a certain direction when it is produced, for example, there is a problem with the rubber cylinder or a certain part of the plate cylinder on the offset press, and the printing quality cannot be guaranteed. , But the rest of the parts are very good. In order to minimize the loss and without affecting the printing quality, it is necessary to move the entire plate center of the printing plate to the left or right when making a plate. Sometimes In order to take care of the offset printing line on the offset printing machine for printing convenience, and the paper cutting on the cutting machine is easy to calculate, without the use of leftovers, causing unnecessary waste, the plate center will also be left when making To the right. For example, when printing Fang Sankai's printed matter, its paper opening specification is 52x54cm. When this kind of printed matter is printed, it is necessary to mobilize the paper rule of the offset press; After the useless parts are cut off, it will not cause waste of paper. It can also save a lot of trouble for the operators on the offset press, why not do it? These all require the plate-making personnel to carefully read the subpoena before making the plate or understand the paper they are going to use for printing. Otherwise, the printing plate will be made according to the routine, which will definitely cause the waste of printing plate or paper.
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