With the increasing maturity of CTP technology, the features of fast publishing speed, good plate stability, and high dot reproducibility have greatly improved the quality of the plate. However, the current use of laser phototypesetters is still relatively common. How to improve the quality of printing under the existing process and equipment conditions, restore the original manuscript information to the maximum, and meet the higher and higher printing quality requirements have become before us. A subject. This article combines the work practice, talks about some experience and experience to improve the quality of printing.
1. Strictly check the quality of plate-making film
Check the operation notice to ensure that the number of plate-making film is complete and the elements are correct; check the film for peeling, scratches, creases, yellowing, and darkening, etc., if problems are found, communicate with the previous process in time and deal with them as soon as possible. For tape printing, scum and dirt on the film, gently wipe it with a clean, soft gauze dipped in alcohol to ensure that the film on the machine is clean.
Second, carefully clean the glass plate of the printing machine
The cleanliness of the glass plate of the plate-making machine has a great influence on the quality of the plate-making. Even a small hair may cause a batch of printing jobs to be scrapped. Therefore, you must carefully wipe the floating dust and fingerprints on the glass plate of the printing machine before printing. For stubborn dirt, such as tape printing, oil stains, etc., you must wipe it repeatedly until it is completely removed. Due to the reflection of the glass plate, inspection of the glass plate from one direction often leaks some dirt, so it is necessary to carefully check from various directions and angles to ensure that the glass plate is clean. In addition, after each printing plate is printed, the glass plate should be re-checked for dirt, and there must be no fluke, otherwise, the quality of the printing plate cannot be guaranteed.
Third, make the printing caliper to improve accuracy
This unit uses Heidelberg CD-102 four-color offset printing machine, the precision requirements for the printing plate: bite error ≤0.1 mm, side gauge error ≤1.9 mm. Since the distance of 0.1 mm can hardly be controlled by the naked eye, it is difficult to grasp with a scale. In order to reduce the error and improve the precision, the self-made plate-making caliper of the abandoned PS version is used. Its width is consistent with the bite, the length is equal to the plate width, the production is simple, the operation is convenient, and the precision and working efficiency of the plate-making are greatly improved after use. [next]
Fourth, accurately grasp the exposure time of the printing
Take 3000W iodine gallium lamp light source as an example.
1. Determine the exposure time according to the thickness of the photosensitive layer of the PS plate. Under normal conditions (temperature 22 ± 5 ° C, humidity 60%, developer concentration 14%), for the PS plate with a moderate thickness of the photosensitive layer, set the exposure time to 120s. However, if the photosensitive layer of the PS version is thicker, such as the fully open PS version, it will increase about 20% than the normal exposure time; if the photosensitive layer of the PS version is thin, such as the 920mm × 760mm PS version, the exposure time will be reduced by about 15%.
2. Determine the exposure time according to the film dot size. Taking the printed version of the urban tourism map as an example, the minimum dyeing dots in the map are 4% -5%, and the maximum dots are 50% -60%. Under normal conditions (temperature 22 ± 5 ℃, humidity 60%, development) The concentration of the liquid is 14%). The relationship between the exposure time and the percentage of dots is as follows:
The exposure time should generally be controlled between 70s-200s, the exposure time is less than 70s, the layout is easy to get dirty on the bottom shadow; if the exposure time is greater than 200s, the dots are easy to lose, affecting the dot reproducibility.
3. Determine the exposure time according to the film condition. If the film is outdated, yellow or dark, or there are multiple splices, the exposure time should be increased appropriately, and if necessary, a second exposure should be initiated.
4. Determine the exposure time according to the indoor temperature conditions. The best indoor working temperature is 18 ℃ -25 ℃. If the temperature exceeds 25 ° C, reduce the exposure time appropriately; if the temperature is below 18 ° C, increase the exposure time appropriately. In addition, the exposure time should be organically combined with other plate-making parameters, and the increase or decrease of the exposure time should be based on the principle that the original manuscript is reproduced realistically, and the layout cannot afford the shadow.
V. Reasonable preparation of developer concentration
Taking the Huaguang Yangtu PS version developer as an example, the concentrated solution is prepared with strong alkali and weak acid salt, and has the advantages of fast development speed, stable performance, good dot reduction, and clean rinse plate. At normal temperature (18 ℃ -25 ℃), the developer is prepared according to the concentrated solution: water = 1: 7; at room temperature above 25 ℃, the developer is prepared according to the concentrated solution: water = 1: 8; at room temperature below 18 ℃, then According to the concentrated solution: water = 1: 6 to prepare the developer solution. The concentration of the developer should not be too high or too low, otherwise it will cause excessive development to destroy the dot reducibility, or insufficient development to cause the shadow. Observe the prepared PS version with a magnifying glass. Once it is found to be a slight base shadow, immediately release the developer and reconstitute it. [next]
6. Organic coordination of various plate-making parameters
Currently, TUNG SHUNG 130 PSBN automatic plate-making machine is used for development. According to the indoor environmental conditions, mainly temperature, dry humidity, cleanliness, and exposure time, developer concentration, scientifically and rationally set and adjust the development temperature and development time. The relationship between these plate-making parameters is not static and must be coordinated with each other according to specific conditions. For example, if the development density is high, the development time should be reduced accordingly; if the exposure time is long, the development time should be shortened; if the temperature is too low, the exposure time or development time should be increased. The adjustment of various plate-making parameters should be based on the principle of clean layout and true reproduction of originals.
In summary, every link of printing should be carefully and meticulously grasped, not only rich work experience, but also a high sense of responsibility and professionalism, so as to improve the quality of printing and lay a solid foundation for further improving the quality of printed products basis.
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