Problems and solutions in offset printing
Time:2022-11-14
Views:3182
The specific problems that may be encountered in the offset printing process and the solutions are as follows:
1. Get dirty
The transfer of ink to another piece of paper because the printing speed is too fast for the ink to cure. In the process of high-speed rotary offset printing, the paper from the first imprint roller to the second imprint roller as long as 0.1s, it is easy to get dirty. There are paper accumulation pressure is too large, also prone to dirty phenomenon. Therefore, the production should pay attention to reduce the pressure of printing, reduce the amount of ink, add paraffin and other organic matter to change the nature of the ink so as to prevent dirty.
2. Dries too slowly
If the desiccant in the ink is not enough, the drying speed of the linking material is slow, the workshop humidity is high, it will lead to the ink can not dry in time, which is prone to dirty. In the printing process, desiccant can be properly added, water supply can be reduced, quick drying ink can be replaced, the relative humidity of the workshop can be lowered, and air circulation can be maintained.
3. Deinking
Deinking refers to the imbalance of ink balance in the printing process, resulting in part of the ink on the ink roller replaced by water instead of ink. If the acidity of the moistening solution is too large, a layer of phosphate will be formed on the surface of the metal roller after wetting the metal roller, which will reject the ink. The problem can be solved by reducing the water supply, reducing the concentration of the liquid or adding ink diluent.
4. The paper is shedding fur or powder
During printing, small fibers or particles fall from the surface of the paper and accumulate on the graphic part of the blanket, which will cause the printing quality to deteriorate. The problem can be caused when the quality of the paper is too poor, the printing force is too large, the water supply on the plate is insufficient, the printing speed is too fast, the rubber blanket is too hard, and the friction between the paper and the rubber blanket is too great. It can be solved by replacing the paper, reducing the printing pressure, adjusting the water supply of the plate liquid, replacing the ink with less viscosity, using a smooth rubber blanket with good elasticity, reducing the printing speed, scrubbing the rubber blanket and printing plate in time and other methods.
5. Stack the ink
Stack ink refers to the accumulation of ink in the printing process on the printing plate, roller and blanket, resulting in the dot paste, can not be smoothly printed phenomenon. This phenomenon can be seen from the change of the ink film on the roller, the ink film becomes thick and the surface of the dull. This is because after the ink is emulsified by the moistening liquid, the binder loses the function of carrying pigment, and the ink becomes slurry, which eventually leads to poor ink distribution, poor transfer performance, or the pigment content in the ink is too high. In multi-color printing, if the post-printing ink viscosity is too large, or the pigment water resistance is too poor, in the bonding material dispersion is not completely wet, the relative density is too large, the amount of oil absorption is small, the amount of ink is too much, the balance of oil and water is improper, ink overprinting is not up, it will also accumulate on the blanket. If the ink pile phenomenon occurs, after analyzing the reasons, we can provide targeted solutions. Such as adding appropriate, more viscous bonding materials, additives and so on to improve the water resistance of ink, reduce the amount of ink, reduce the amount of liquid, reduce the acidity of the liquid, replace with good quality paper, choose the right pigments.
6. Text thickens
When the text becomes thick, the printing looks very oily, dot and line are wider and larger. The reasons are too thin ink, oil is too large, the acid value of the linking material is too high, the acidity of the liquid is too weak, the pigment is not dispersed in the ink, the ink water resistance is too strong, the ink additives are not suitable. Can be added in the ink viscous bonding material, increase the water supply, improve the solution acidic solution.
7. Spots
Printing color some light and some deep, this color distribution is irregular, some regular. The appearance of spots is due to the irregular surface of the paper, the ink is too transparent; Printing pressure is too large, the ink will be pressed into the concave part of the paper surface; If colored water droplets stick to the plate in the field, they form snow flecks. Thicker ink can be used, the printing pressure is smaller, the surface is smooth and uniform paper and good water resistance ink, as far as possible with opaque ink to solve.
1. Get dirty
The transfer of ink to another piece of paper because the printing speed is too fast for the ink to cure. In the process of high-speed rotary offset printing, the paper from the first imprint roller to the second imprint roller as long as 0.1s, it is easy to get dirty. There are paper accumulation pressure is too large, also prone to dirty phenomenon. Therefore, the production should pay attention to reduce the pressure of printing, reduce the amount of ink, add paraffin and other organic matter to change the nature of the ink so as to prevent dirty.
2. Dries too slowly
If the desiccant in the ink is not enough, the drying speed of the linking material is slow, the workshop humidity is high, it will lead to the ink can not dry in time, which is prone to dirty. In the printing process, desiccant can be properly added, water supply can be reduced, quick drying ink can be replaced, the relative humidity of the workshop can be lowered, and air circulation can be maintained.
3. Deinking
Deinking refers to the imbalance of ink balance in the printing process, resulting in part of the ink on the ink roller replaced by water instead of ink. If the acidity of the moistening solution is too large, a layer of phosphate will be formed on the surface of the metal roller after wetting the metal roller, which will reject the ink. The problem can be solved by reducing the water supply, reducing the concentration of the liquid or adding ink diluent.
4. The paper is shedding fur or powder
During printing, small fibers or particles fall from the surface of the paper and accumulate on the graphic part of the blanket, which will cause the printing quality to deteriorate. The problem can be caused when the quality of the paper is too poor, the printing force is too large, the water supply on the plate is insufficient, the printing speed is too fast, the rubber blanket is too hard, and the friction between the paper and the rubber blanket is too great. It can be solved by replacing the paper, reducing the printing pressure, adjusting the water supply of the plate liquid, replacing the ink with less viscosity, using a smooth rubber blanket with good elasticity, reducing the printing speed, scrubbing the rubber blanket and printing plate in time and other methods.
5. Stack the ink
Stack ink refers to the accumulation of ink in the printing process on the printing plate, roller and blanket, resulting in the dot paste, can not be smoothly printed phenomenon. This phenomenon can be seen from the change of the ink film on the roller, the ink film becomes thick and the surface of the dull. This is because after the ink is emulsified by the moistening liquid, the binder loses the function of carrying pigment, and the ink becomes slurry, which eventually leads to poor ink distribution, poor transfer performance, or the pigment content in the ink is too high. In multi-color printing, if the post-printing ink viscosity is too large, or the pigment water resistance is too poor, in the bonding material dispersion is not completely wet, the relative density is too large, the amount of oil absorption is small, the amount of ink is too much, the balance of oil and water is improper, ink overprinting is not up, it will also accumulate on the blanket. If the ink pile phenomenon occurs, after analyzing the reasons, we can provide targeted solutions. Such as adding appropriate, more viscous bonding materials, additives and so on to improve the water resistance of ink, reduce the amount of ink, reduce the amount of liquid, reduce the acidity of the liquid, replace with good quality paper, choose the right pigments.
6. Text thickens
When the text becomes thick, the printing looks very oily, dot and line are wider and larger. The reasons are too thin ink, oil is too large, the acid value of the linking material is too high, the acidity of the liquid is too weak, the pigment is not dispersed in the ink, the ink water resistance is too strong, the ink additives are not suitable. Can be added in the ink viscous bonding material, increase the water supply, improve the solution acidic solution.
7. Spots
Printing color some light and some deep, this color distribution is irregular, some regular. The appearance of spots is due to the irregular surface of the paper, the ink is too transparent; Printing pressure is too large, the ink will be pressed into the concave part of the paper surface; If colored water droplets stick to the plate in the field, they form snow flecks. Thicker ink can be used, the printing pressure is smaller, the surface is smooth and uniform paper and good water resistance ink, as far as possible with opaque ink to solve.
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