Gravure failure and analysis (below)

2) Viscosity The viscosity of the ink is too large, which will cause it to increase the impact on the blade, so that the blade cannot completely clean the ink.
Drying nature Gravure ink is a volatile drying type, so its dryness is also the volatility of the solvent. When the ink is excessively dry and the solvent volatilizes too quickly, the friction between the printing plate and the blade is relatively increased, which makes it difficult to scrape the blade. The ink of the lower plate will cause the knife line, but too late drying, that is, the slow evaporation of the solvent will cause the non-graphical part of the ink to be transferred to the substrate to form a plate. Therefore, the solvent must be evaporated at a moderate speed. In the analysis of viscosity, it was mentioned that a solvent with a quick volatilization was used, and there was a contradiction in that it was possible to solve the problem of excessive drying by adjusting the pressure and angle of the doctor blade. The gravure ink was also selected as a solvent with high solubility and fast evaporation. For better, ethyl acetate, ethanol, etc.
4) In fact, this hardness can be attributed to fineness. For pigments with high hardness, such as red and blue, even if they are opened, they cannot reach a very small particle size, and they are easily scratched and damaged. This inevitably results in a knife line. Then, when using red and blue inks, it is necessary to set a fine degree of fineness. When buying inks, try to provide suppliers with finer inks, and then pre-select the preventive measures to prevent other factors from affecting inks. Fineness, with attention to the condition of the blade, guarantees the integrity of the blade.
5) Activity In the production of ink, a certain amount of active agent is generally added. There is also a certain activity after the plate cylinder has been chrome plated. If the activity of the ink or the plate cylinder is too high, the active material does not adhere strongly to the plate cylinder during printing, and the scraping blade is also very difficult to scrape, thereby forming a cutting line. In this case, the knife line is meteor-like or microfilament-like. There is a certain degree. At this time, the plate cylinder can be washed and cleaned first to remove the active material on the surface, and then the surface active agent can be added to eliminate the knife . When using this additive, it is preferable to use an ink circulation system so that it is repeatedly used.
The quality of the ink has a great influence on the knife line. When the conditions permit, it is better to use higher ink. To ensure the proportion of fresh ink, just pay attention to the series of measures mentioned above for purchase and use. The knife line problem is It is not difficult to solve.
3. Environmental conditions It is very important to maintain a good environment in gravure printing workshops. The environment here mainly refers to dust and temperature and humidity.
1) Dust and dust will produce thin knife lines. The plastic film will generate electrostatic adsorption during printing. The dust will return from the film to the printing plate cylinder during printing. When the dust gathers in the ink, it will adhere to the blade and create a knife. line. To this end, static eliminators should be installed. Above the plastic substrate film, anti-static screens or electrostatic belts should be suspended to increase the humidity in the air to reduce electrostatic adsorption.
Dust may also originate directly from the air, which requires a good hygienic environment in the printing shop: the printing presses are placed, the workshop is isolated from the outside world by wind curtains, the number of people in the workshop is controlled, wet ground is often used to mop the ground, and the ground is used exclusively Paint treatment to prevent dusting. In the maintenance of the machine, it should also be noted that the ducts and other unattractive parts are usually cleaned to prevent dust accumulation. For the dust in the ink, a filter device can be added to the ink circulation system to clean the ink tank and the ink tank. When the old ink is used, under the premise of ensuring quality, 1/3-1/2 old ink can be used, but it is better not to use the old ink completely, and to filter it with a metal wire net with more than 120 mesh before the old ink.
2) Temperature and humidity conditions In fact, this factor has been included in the previous article, here to analyze.
The temperature is too high, the solvent volatilizes too quickly, the solvent balance is unbalanced, and the drying is excessive; the ink solution is poor, the viscosity becomes large, and the ink scraping is difficult, both of which can easily cause the knife line.
Therefore, the gravure environment should be kept as close as possible, install air filters and dust content determination, install air conditioners to maintain the environment temperature and humidity stability.
Through the above analysis, we can see that there are many factors in the production of knife lines, and are related to each other, such as plate cylinder and squeegee, squeegee and ink, ink and environment, knife line also often with the version of contamination, paste version, etc. Phenomenon occurs at the same time, so it is often difficult to judge when the fault is caused by various factors, the solution can not be specified, but as long as the different characteristics of the knife line, through the judgment method mentioned above, grasp the major aspects of the main spring Influencing factors and taking corresponding solutions can eliminate it. Of course, the most ideal state is to proceed from the factors that create the knife line involved in this paper to reverse thinking, and take all measures to prevent it from occurring to reduce the incidence of knife lines.