Plate printing in printing Traditional plate printing equipment is simpler and less expensive than printing equipment. On the surface, its operation complexity and maintenance cost are not as great as its before and after procedures.
I saw at a factory in Guangxi that there were eight-color offset printing presses, four-color Heidelberg, four-color Roland and four-color Komori printing equipment in the printing process. The house used an old obsolete double-sided plate-making machine. The factory modified the power of the iodine gallium lamp to 4000W. The plate is too close to the light source (the distance between the light source and the plate is not adjustable). The four corners are more than 50% different from the illuminance. The uniformity of the PS plate produced by such a plate making machine can be imagined. We asked the quality control staff with the color prints of different colors printed by the factory. They said that they always thought that the printing machine was caused by "exhaust air", because there is no illuminance meter, so I don't know the difference in illuminance is so big . In fact, the problem of not paying enough attention to the quality of printing is basically the problem. If there is no illuminance meter, you can use the gray ladder ruler to take points to detect. It can also be seen that the exposure of the entire layout is very different from the four corners due to the different illuminance.
As a process in the printing process, the printing plate is as important as the previous and subsequent processes, and plays a very important role in the process of printing quality control. From the perspective of the production process of printed matter, the quality of each process from the beginning of the manuscript to the finished product will have an impact on the quality of the finished product. But in principle, the pre-process will affect the post-process, and the quality of the post-process will not affect the pre-process.
For example, as the pre-printing position of the printing process, the high-gloss ideas on the printing plate were "flyed" during the printing process. When reaching the post-printing position, no matter how high the technology of the printer is, the number of printing equipment used Okay, it ’s gone. In the same way, 98% to 97% of the small white dots in the subtle levels of the dark tone are printed and pasted during the printing, and there is no room for recovery in the printing process. In short, any quality consequences of the pre-press process are exposed in the post-process, and there is no room for repair, or room for correction is very small. In addition to the above obvious faults in printing quality, there are still many faults that are not easy to find, such as: the quality of the original (film), the quality of the PS version of the manufacturer, the quality of the light source of the printing machine, the technical level of the operator, the environment of the printing room (Including: temperature, humidity, water cleanliness, stability of power supply voltage) and operating environment (such as standard working light source), maintenance, maintenance, management system, sanitary conditions and other factors all more or less affect the quality of the printing work Make an impact.
The impact on the color density and color saturation of the printed matter; in the entire printing and copying process, making full use of the whiteness of the paper and the saturation of the ink is the work goal and principle of copying the printer, and the printing job is also insisting on and implementing this principle. An important link. Experienced printing managers and teachers often emphasize that the original graphics, including the "whether the dots are strong and the ideas are strong" on the PS version, shows that the density of dots has a great impact on the copying work.
Some companies, even small workshops, do not meet this standard for output film density.
If the plate-printing machine is also of the low power and the light source of the tube (indoor lighting design composition) is not standard, the printed version of the PS version of the text will not come to ink, this surface will show the expression of no ink The color density and color saturation can not reach the color effect of the original, like "big water", the color is not bright.
There are many factors that affect the quality of the printing version. The factors that affect the quality of the positive PS version can be divided into printing equipment, plate material, operation, environment, original version, suction vacuum, etc. The degree of tightness must be tight, the degree of vacuum Must meet the standard, there must be a second pumping. The light source requires high power and high illuminance. For example, the lithography machine with 4000W ~ 8000W power should pay attention to the uniformity of the light source and reach the technical parameters given in the manual. The industry standard is ≥85%, and the domestic export type generally gives a uniformity of ≥95%. It is rarely achieved in the machine tested by the author, including some imported printing machines, which can reach ≥85%. Not bad. Among the devices tested by the author, Shanghai Xinxing Exposure Machine can reach this standard. We found that the printing machines used by many domestic printing companies did not meet the qualification standards. The PS plates that were printed out were unevenly illuminated, and the center and the four corners of the plate were exposed to different intensities of light, resulting in different dot density. When printing some small versions When the large version is assembled, the graphics in the middle and the four corners will have a significant color difference.
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