How to control the problem of dot gain in offset printing

The phenomenon of dot gain in printing is inevitable, but it can be controlled. Under normal circumstances, the fine print dot gain of coated paper is less than 12%, the general print is less than 18%, and the print control is within 35% (generally 50%). In the production process, effective control can be made from the following aspects.
1. Select high quality media, reasonably control exposure time and developer concentration
The clear printing plate of the dried printing plate is clear and the outlets are strong, so as to ensure the transfer effect of the outlets and ensure that the printing plate has a higher resistance to printing forces. Under normal circumstances to ensure that 5% of the network is not lost, 95% of the network is not blurred.
2. Strictly control the ink and water balance in printing
In the printing process, if the water supply is too large, the ink supply on the layout will increase, the ink layer will become thicker, and the ink emulsification will be severe, resulting in dull and dull prints. In the production process, in order to reduce the start-up waste, the water level is usually increased to 150% of the normal value when the machine is turned on. After normal printing, the amount of water should be gradually reduced to the normal value to ensure clear graphics and saturation.
3. Control various printing pressures within a reasonable range
The pressure between the plate cylinder and the blanket cylinder is controlled between 0.15 and 0.20mm, and two printing rollers are parallel to the printing plate roller. The printing roller width between the plate roller and the plate roller with a diameter of 100mm or less is 3 ~4mm, the printing roller width of printing plate roller is 5~6mm.
4. Correctly control the concentration of fountain solution
The control of the fountain solution concentration plays a crucial role in the balance between ink and ink and the quality of the printed product. A suitable concentration of fountain solution can quickly flush away the "dirt" around the dot. If the concentration of the fountain solution is too low, the ink around the dots cannot be removed, and if the dots are light, the dots will increase, and when the weight is too high, the stencil will be caused. If the concentration of the fountain solution is too high, the resistance of the PS plate will be reduced and the fountain solution will be reduced. A lot of waste. In general, the pH of the fountain solution is controlled between 4.0 and 6.0, and the conductivity is controlled at 1400±200 μs.

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