1. Observing proofs <br> During the printing process, the amount of ink supply and water supply determined during the trial printing will always have some changes. It is necessary to carry out regular high-speed sampling of 500-1000 sheets, often focusing on the printed samples. Overprint and ink conditions. Ink inspection can generally compare the two sides of the printed sample with the middle part, and can also compare the ink color of the printed sample and compare it with the sample of the previous several times. If there is a change, fine tune the ink supply system. Also notice whether there is a change in the layout moisture. The inspection of the rules, especially the inspection of the first color of the monochrome machine, can often take 20-30 impressions and stagger them to observe whether the rules are consistent and whether the positioning of the front gauge and the side gauge is correct. . After a period of continuous printing, dirt such as paper powder, paper fluff, and ink and ink on the paper is easily attached to the printing plate or blanket, resulting in lines, text breaks, missing strokes, or graphics. Dirty, if there is such a situation, should wipe off the paper, ink and other dirt, to prevent downtime caused by ink changes, generally should put 8-10 overprinted blotter paper and then continue printing. At the same time, attention should be paid to checking the printed products and observing whether the back of the printed products is dirty or not. For printing products with a large graphic area and a relatively thick ink layer, measures should be taken to spray the powder and dry the splint.
2. Cleaning blanket
After several thousand sheets of continuous printing, due to the increasing thickness of paper powder, paper, and ink sheets accumulated on the blanket, the ink transferability is getting worse and worse. The ink of printing samples becomes shallow and rough, and the layers gradually become unclear. The outline is blurred. In this case, stop the machine immediately and clean the blanket. There are manual and automatic methods for cleaning the blanket. During manual cleaning, wipe the machine with a cloth impregnated with gasoline. After the dirt has dissolved, remove the dirt with a clean cloth. For automatic cleaning, first pull the handle of the cleaning device to make the cleaning roller and the blanket cylinder come into contact with each other, then fill the pressure roller with gasoline through the oil filling pipe, clean the blanket, and the dirty oil that is washed off is transferred to the driving roller and finally scraped Scrape in the oil tank. At the same time, care should be taken to keep the blanket flat and there should be no pits.
3. Into the warning paper <br> During the printing process, the mark should be marked in the place where the fault is found, so that it can be checked in the post process. The method is to place warning papers marked with "dirty" or "overprinting" on the paper pile.
4. Note the change in layout water
The printing plate should maintain a moderate amount of water during the printing process. If the amount of water in the layout is large, the ink will be emulsified seriously, the blot will lose its luster, the lines will fade, the ink will dry slowly, the paper will stretch, and overprinting will be inaccurate. If the amount of layout water is too low, the blank will be easy to get dirty. The layout should be observed according to the sampling or layout brightness. Change the amount of water and adjust it in time. When the water volume is too large, the speed of the bucket must be reduced; when the amount of water is insufficient, the speed of the roller must be increased.
5. Pay attention to the change of ink
(1) Note 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, and in order to maintain the stability of the ink amount, the amount of ink in the ink fountain must be constantly maintained. The ink has thixotropy, and it is necessary to frequently stir the ink with an ink scoop or install a stirrer so that the ink maintains good fluidity.
(2) Pay attention to the ink color of the printed product. The ink color of the printed product will be different when the water supply quantity, ink supply quantity, workshop temperature and humidity, machine operation condition and other factors are slightly changed. Therefore, frequent sampling is required during the printing process and it will be compared with the standard ink of the test printing. During the printing process, the operator must insist on the operation of Sanqin, that is, diligently check the printed sheets, diligently observe the amount of water in the layout, and frequently mix the ink in the ink fountain. In addition, the ink on the ink roller should be cleaned when changing the color, especially when the dark ink is changed to light color ink.
6. Pay attention to the change of the printing plate <br> Pay attention to whether the shallow fine spots at the shining place of the printing plate are worn, and need to replace the new one; pay attention to whether there is any scratch on the plate and whether the printing plate is loosened.
7. Measures to Take When a Long Time Stops <br><br> In the event of a long downtime such as waiting for a rest, etc., the following measures must be taken:
(1) Protect the printing plate. Grub the gum arabic on the surface of the plate, taking care not to leave bubbles on the plate, and the adhesive must not adhere to the blanket.
(2) Prevent the ink from drying out. To prevent surface drying of the ink in the ink fountain and the ink roller, a drying inhibitor may be sprayed on the ink surface.
(3) Storage of semi-finished products. Semi-finished products should be stored in an airtight, dark-proof workshop to prevent paper deformation and overprinting.
8. Pay attention to the printing abnormalities in the operation of the printing machine
Should pay close attention to the possible abnormalities in the operation of the offset press, such as the abnormal noise emitted by the machine in the second flight, the temperature of the bearing and the frame, the vibration of the whole or part of the machine, and the obstruction of the oil in the machine. In the event of an abnormality, maintenance should be stopped in time.
Process and precautions in the printing process
January 23 07:07:27, 2024
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