Problems that should be noted in printing operations
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1. Observe the proofs
During the printing process, the amount of ink supplied and the amount of water supplied in the trial printing will always change somewhat. It should be re-adjusted by sampling the sample. Usually 500 to 1000 samples are taken. The focus is on observing the color and ink of the sample. Ink inspection generally compares the two sides of the print to the middle, or prints the print off the ink for comparison, and can be compared with the previous prints. If there is a change, fine-tune the ink supply system. Also pay attention to whether the moisture in the layout changes. The inspection of the rules, especially the inspection of the first color of the monochrome machine, can often take 20 to 30 prints, and the bite is smashed open to see if the rules are consistent. The front gauge and the side gauge are positioned. accurate. After continuous printing for a period of time, the paper powder, paper wool and fine ink in the ink and other dirt, easy to adhere to the printing plate or rubber, causing the text lines broken, missing or the text is dirty, such as In such cases, the ink paper hair should be wiped off. To prevent the ink color from changing due to the shutdown, it is generally advisable to put 8 to 10 sheets of blotting paper before continuing printing. At the same time, you should always pay attention to and check the printed products, and observe whether there is any sticky phenomenon on the back side. For printed products with large ink layer thickness, you should take the measures of dusting and drying.
2. Cleaning the blanket
After continuous printing for a long time (thousands of sheets), as the ink, powder and paper wool accumulate on the blanket, the ink transferability becomes worse and worse, and the ink on the print becomes shallow and rough. Unclear, the outline is blurred. At this point, stop immediately and clean the blanket. There are two ways to clean the blanket: manual and automatic. When cleaning by hand, while jogging the machine, wipe it with a cloth dipped in gasoline. After the dirt is dissolved, remove the dirt with a clean cloth. When cleaning automatically, firstly pull the handle of the cleaning device to make the cleaning roller and the blanket cylinder contact, then inject the gasoline into the pressure roller through the oil filler tube, clean the blanket, and the dirty oil washed is transferred to the driving roller, and finally the blade is scraped. Scrape into the oily tank. Also note that the blanket is flat and there should be no pits.
3. Clip the warning paper
During the printing process, the place where the fault is found shall be marked with a mark to be inspected in the post-process. The method is to use a warning paper with the words "dirty" and "overprinting" marked with eye-catching colors in the paper pile.
4. Pay attention to changes in water supply
The printing plate should maintain a moderate amount of water during the printing process. If the amount of water in the layout is too large, the ink is heavily emulsified, the print is tarnished, the line is creased, the ink is dry slowly, the paper is elongated, and the overprint is not accurate; if the amount of water is too small, the blank portion is easily dirty. The change should be observed according to the brightness of the sample or the layout and adjusted in time. When the water volume is too large, the rotation speed of the water bucket roller should be reduced; when the water volume is insufficient, the rotation speed of the water bucket roller should be accelerated.
5. Pay attention to changes in ink
Pay attention to the ink in the ink fountain: the ink in the ink fountain naturally flows by its own weight, and the amount of ink discharged depends on the gap between the ink fountain and the ink fountain blade. Therefore, the amount of ink contained in the ink fountain directly affects the amount of ink discharged, and the amount of ink in the ink fountain is often maintained in order to maintain the stability of the ink discharge amount. In addition, the ink has thixotropic properties, and it is necessary to constantly stir the ink with an ink shovel (or install a stirrer) to maintain good fluidity of the ink. Pay attention to the ink color of the printed matter: the ink color of the printed matter will be different when there are slight changes in the amount of water, the amount of ink supplied, the temperature and humidity of the workshop, and the operation of the machine. Therefore, in the printing process, it is necessary to compare the standard ink color with the test sample frequently. In short, in the printing process, the operator must adhere to the three-dimension operation, that is, check the printed sheets, observe the moisture of the plate, and stir the ink of the ink fountain. In addition, the ink on the ink roller should be cleaned when changing colors, especially dark ink for light ink.
6. Pay attention to the changes in the plate
Pay attention to the shiny area of the printing plate. If you want to change the small mesh point, you need to change the new version. At the same time, pay attention to whether the layout has scratches and whether the printing plate is loose.
7. Measures to be taken during long downtime
Long-term shutdown, such as the same version, work breaks, etc., need to take the following measures: (1) protection plate measures: to rub the gum arabic on the surface of the plate, and be careful not to leave bubbles on the plate, glue Can't stick to the blanket. (2) Prevention of ink drying: In order to prevent the ink surface in the ink fountain and the ink roller from drying, a drying inhibitor may be sprayed on the surface of the ink. (3) Semi-finished product storage: Semi-finished products should be stored in a closed, non-sun-facing workshop and compacted to avoid paper deformation and affect the fit.
8. Pay attention to the printing anomaly in the printing machine operation
Pay close attention to possible abnormalities in the operation of the offset press, such as abnormal sound from the machine during operation, temperature at the bearing and frame, vibration of the machine or part of the machine, oil blockage on the machine oil line. When an abnormality occurs, it should be shut down for maintenance.