Troubleshooting of deinking in the hottest offset

2022-08-14
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The deinking failure and troubleshooting of offset press

the deinking failure of offset press often makes the inking roller unable to ink or the ink transmission system abnormal, and the printing plate cannot get a uniform ink surface pattern, which brings great trouble to production. The reasons for the deinking failure of offset press are as follows: 1) the ink viscosity is small, the ink filament is short, the oil property is poor, and the water content of the plate is too large; 2) The fountain solution is too acidic; 3) The glue content in the fountain solution is too large; 4) The temperature in the workshop is too low

1. low ink viscosity

low ink viscosity and short ink filament are mainly due to the decline of the performance of the fountain solution after a period of use of the ink prepared with other auxiliary materials in the diluent. After the high-speed extrusion of the ink roller, it emulsifies with the ink. The over emulsified ink brings the water bucket acid to the surface of the ink roller, which erodes the surface of the ink roller and produces a new water layer, thus discharging oil and deinking. Similarly, inks with poor oiliness are also the main form of deinking, but the root cause of the process is the poor manufacturing of inks or defects in the process. When the moisture content of the layout is too large, it will cause deinking failure. The possibility of deinking failure caused by high moisture content in a simple layout is relatively small

treatment: for deinking failures caused by low ink viscosity and short ink filaments, you can add a known amount of concentrated inking oil to the ink; For the deinking failure caused by poor ink oiliness, you can add a known amount of thin inking oil. In either case, try to reduce the moisture in the layout and avoid excessive emulsification of the ink

in fact, an appropriate amount of water and ink mixing and emulsification is conducive to offset printing, and under the high-speed rolling of ink rollers and the interaction between ink and fountain solution, absolute oil-water separation is also impossible. The emulsification degree of offset printing ink is about 20%, which is commonly referred to as the state of water in oil, so that the fountain recognition and ink are basically in balance. Therefore, the real ink emulsification fault should be excessive emulsification

2. the fountain solution is too acidic

the deinking failure caused by the strong acidity of the fountain solution mainly has two aspects: first, the acidity is too strong, the surface tension of the fountain solution is very small, and a large amount of water is dispersed in the ink, which greatly exceeds the optimal water content of 20%, which destroys the balance between the fountain solution and the ink, After the experiment of the final layer, the curve can be amplified by the graphics processing module for data reanalysis, and the deinking fault can be caused; Second, the acid is too strong, and the fountain solution accelerates the dissolution of ink pigments and paper coatings, producing too much calcium salt, which makes it difficult to transfer the ink and causes deinking due to unbalanced emulsification

treatment: control the pH value of the fountain solution at about 5

3. Too much Arabic gum is added to the fountain solution

adding an appropriate amount of Arabic gum, which directly measures the two true distances of the original gauge distance as the distance after break, can improve the wettability of the fountain solution, but if the amount is too much, it will increase the emulsification degree of the ink, and eventually lead to excessive emulsification of the ink and deinking failure, because Arabic gum itself is also an emulsifier

treatment: re prepare the fountain solution as required

4. The workshop temperature is too low

the deinking fault caused by the low gradient of the workshop is generally hidden and difficult to find. But this kind of fault has two characteristics: 1) it usually occurs in winter, especially when the temperature is lower than 3 ℃; 2) It is highly regional, and the occurrence area is mostly the junction zone between the South and the north

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