First, print twice, observe the overprint accuracy, check and adjust the side gauge pulling force, paper feeding, paper pressing wheel and paper pressing machine. Then check the tension of the blanket. The new blanket is easy to relax. Pay attention to tighten it by stages, but it should not be too tight. Check the drum lining and printing pressure again.
And then reduce the viscosity of the ink. Ink viscosity is high, the paper can not be smoothly stripped blanket, so that the tip of the paper is unstable, resulting in ghosting. Can be appropriate to reduce the viscosity of the ink. Then there is the adjustment of the teeth. The poor adjustment and improper maintenance of the teeth are the main causes of the double image. Therefore, it is necessary to adjust and maintain the teeth regularly to keep them in good working condition.
1. Pay attention to the sample
First, sample inspection in printing. Shortly after entering the formal printing, the ink supply and water supply determined at the start of printing will change, so it is necessary to conduct frequent sampling inspection and readjustment. When the printing speed remains unchanged and the ink supply and water supply are in a stable state, the sampling inspection shall be carried out according to the proportion of 500 ~ 1000 sheets per printing. Then insert a warning note into the printed product. In order to facilitate the inspection in the later process.
2. In the early stage of printing, the printing factory should pay attention to the change of water loading
First of all, pay attention to the change of water filling in the early stage of formal printing. There will be some changes in the amount of water applied during the trial printing and after the formal printing. Be sure to observe whether the sample sheet has ghosting and water bearing, and adjust the amount of water supplied to the printing plate at the same time. Secondly, we need to pay attention to the change of water supply in the process of formal printing. Pay close attention to the influence of the heating of the main body of the machine and the ventilation of the workshop on the water supply. Pay attention to the cooling device of the wetting system and control the temperature of the wetting liquid. Too little water supply will make the printing plate dirty; too much water supply will cause ink emulsification, which will bring a series of problems.
3. Pay attention to the change of printing ink in the early stage of printing
First of all, we need to pay attention to the ink of the ink bucket. The ink of the ink bucket comes from the gap between the ink bucket roller and the ink bucket scraper, which is naturally squeezed out by the weight of the ink. Therefore, the amount of ink in the ink bucket directly affects the output of ink. In addition, printing ink has thixotropic properties. Always use an ink knife to stir in the ink bucket, or install an ink mixer.
Second, the need to prevent ink drying on the machine. And need to pay attention to ink uniformity, printing density depends on the amount of water, room temperature, machine speed and change. It should be compared with the standard sample sheet frequently. Pay attention to prevent uneven ink. So as to maintain the pH value of the wetting solution, after the auxiliary agent is added to the ink, it is easy to affect the pH value of the wetting solution. If the pH value increases, it is easy to cause the printing plate dirty, so special attention should be paid to it.
4. Pay attention to the dirt on the back during printing
Back rub dirty is due to slow ink drying, graphic ink layer is too thick, paper smoothness and other reasons, so that the ink on the surface of the sheet stick to the back of the previous sheet.
5. How to avoid ghosting and how to deal with it
The so-called double image is to use a plate to print the wrong image, in the sheet can see double, triple image. There are many reasons for ghosting, such as paper, teeth, roller, blanket, printing speed, ink viscosity and other factors are very complex. Generally, the following methods can be used to check the causes and deal with them.
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