Countermeasures for the most popular web offset pr

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Countermeasures to solve the problem of dirty web offset press

web offset press is loved by many printing enterprises because of its high efficiency, strong adaptability to printing books and newspapers and good economic benefits. But in printing, it is often because of ② The problem that the fixture with a small experimental force is dirty affects the product quality. How to quickly judge and solve the dirty phenomenon? After years of machine work and long-term observation and practice to solve problems, I now analyze the causes and solutions of the dirty phenomenon of web offset press, and communicate with your printing colleagues

dirty refers to that the imprint on the printed matter dries slowly, and part of the ink adheres to the paper guide roller, triangle, folding roller and conveyor belt through which the paper belt passes, and is returned to the paper, causing striped oil and ink dirt on the printed matter. There are many reasons for the dirty phenomenon. It is closely related to the paper structure, ink composition, temperature and humidity in the production workshop, water and ink balance during printing, and it is an extremely complex problem

the common causes of soiling are mainly the following:

first, the temperature and humidity of the production workshop

the ink is affected by temperature. The higher the temperature, the faster the ink solidifies and dries; On the contrary, when the temperature decreases, the ink tends to harden, which is easy to cause paper fuzzing and is not easy to dry. The humidity of the printing workshop is another important factor affecting the drying of ink. When the temperature is lower than 20 ℃, the higher the humidity is, the higher the water content of the printing paper is, even if it does not affect the ink. The humidity of the paper itself also affects the drying of the ink. As a result, the ink dries poorly, resulting in dirt

solution: keep 2. Take the rest of the raw materials together with the broken pieces of cross-linked PE cables and PE hollow blow molding products, and put them into the high-speed mixer for mixing. The temperature and humidity in the production workshop are controlled within the range of temperature (23 ± 1) ℃ and humidity (60 ± 2)%

second, the process of transferring paper

after printing, the paper passes through the paper guide roller, triangle, folding roller, conveyor belt and other parts, and the ink accumulation and dirt accumulation in use lead to dragging

solution: clean these mechanisms and always keep them clean

third, the auxiliary agent in the ink is added too much

during printing, due to the large amount of paper powder, the roughening is serious, and the ink absorption is poor. When adding inking oil and viscosity reducer into the ink, the amount is improper, resulting in slow drying and soiling of the imprint

solution: appropriately increase the pad thickness of the printing plate or blanket cylinder, and the amount of auxiliary agent should be within 5%

IV. ink blocking

part of the ink in the ink bucket coagulates and gels due to high temperature, air drying, hardening, crusting or poor connection, and accumulates between the ink output regulating steel sheet and the ink output roller. As a result, the ink volume adjustment is poor, sometimes large and sometimes small. When the ink output suddenly increases, the ink film on the paper will be too thick, which is not conducive to infiltration and drying, and it will be dirty

solution: clean the ink bucket and ink outlet roller, and wash the anti rust oil applied during packaging into good ink

v. there are two situations when the water glue roller is dirty: 1. The oil of the water glue roller is dirty, and the driven needle is turned back to zero, and the ink is seriously dirty; 2. The pH value of the dampened plate in the water bucket cannot meet the printing requirements, and they cannot keep the blank part of the printing plate clean and form oil dirt

solution: clean the water rubber roller; Test the pH value of the fountain solution to make it reach 5 ~ 6

VI. adjustment of water glue roller

due to the pressure adjustment of water glue roller is not in place, or the adjustment system of water outlet roller is abnormal, and the speed is too fast, resulting in the increase of water content of paper and the decrease of ink absorption; The water content of the ink increases, the viscosity decreases, the adhesion is not very strong, and the oil film cannot dry quickly, resulting in dirt. Especially in the case of some papers with high whiteness and poor ink absorption, it is very obvious

solution: adjust the pressure of the water rubber roller to about 4 ~ 5mm (imprinting water marks on the fingerprint plate). Adjust and repair the water outlet roll control system. The key is to master the amount of water in the printing plate and achieve a balance between water and ink

reprinted from: Printing Art Forum

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