1. Small amount of water
The role of the PS version of the wetting fluid is to achieve dampening, cleaning, and purifying the plate surface. The small amount of water means that the water supply amount is controlled to the smallest possible range without affecting the stability of the blank part of the printing plate (that is, the blank part is not sticky), and the water supply amount and the ink amount are in a relatively stable state.
The amount of water (ie, wetting fluid) directly affects the ink, printing plate and paper, and the ink, printing plate and paper directly affect the printing quality. The small amount of water can ensure the consistency of the ink color before and after the color and the stability of the printing operation, which can print a more ideal product. If the amount of dampening fluid is too large, the biggest impact is on ink and paper, followed by the printing plate. If the amount of wetting fluid is too large, it will destroy the water-ink balance state, accelerate ink emulsification, and the ink cannot be transferred normally, or even cause the "pattern" of the layout and the color of the printed ink to become lighter. Too much water on the printing plate surface will cause the inking performance of the graphics and text to be abnormal, the printed image will lose its luster, the color will not be bright, the gradation will be poor, and the product performance will be flat. Excessive amount of wetting liquid will affect the printing performance of the paper, causing the paper to fluff and de-powder; excessive moisture content of the paper will cause the paper to expand and contract, affecting the quality of the overprint; in addition, excessive moisture content of the paper will cause the paper to change Soft, resulting in uneven paper collection, slow drying of the blotting ink layer, and the back side of the paper is sticky.
It is more important to estimate the water consumption of the layout in advance than to adjust it afterwards. It is an important prerequisite for adjusting the water-ink balance of the layout. Therefore, the main factors affecting the amount of wetting fluid should have a more important understanding before determining the amount of water on the plate. In actual production, the amount of wetting fluid depends on: the graphic area distribution of the layout; paper properties; ink properties; machine speed; ambient temperature and humidity and air circulation.
2. Low pressure
Printing pressure is the first condition to complete offset printing. Whether the pressure between cylinders is ideal is the key to ensuring the printing quality. Small pressure means that the pressure can reduce the printing pressure between the cylinders as much as possible on the basis of ensuring the good transfer of the ink (that is, ensuring that the printed matter is strong in the imprint, the dots are full but not spread, and the tone level is clear and rich). Whether the pressure is low (that is, using ideal pressure) is one of the important signs to measure the level of technology, and it is also an important condition for ensuring high quality and high yield.
Excessive printing pressure has a great impact on product quality. Excessive pressure can easily cause dot deformation, paste, thick ink color, and even image distortion. Excessive pressure will also accelerate plate wear and roller wear.
The best printing pressure adjustment method is to make the gear in the standard meshing state and achieve the best printing suitability by changing the thickness of the pad.
When printing thick paper, the best method for adjusting the printing pressure is to reduce the blanket thickness of the rubber cylinder accordingly and increase the blanket thickness of the plate cylinder. Minor differences can be adjusted by changing the center distance between the cylinders and readjusting the ink roller pressure.
The most commonly used and most straightforward method of printing pressure inspection is the bar method. The specific operations are as follows: lift the water roller, drop the ink roller, run the machine at low speed and press together, and wait until the surface of the three rollers is evenly inked, and then you can stop. Each roller has an ink bar at the parking place, such as the width of the ink bar is uniform within the value range given by the machine, and the width of the ink bar of the impression cylinder and the rubber cylinder is greater than the width of the ink bar of the plate cylinder and the rubber cylinder , It means that the pressure adjustment is uniform and appropriate. If the width of the pressure bar is wide and narrow, the biggest possibility is that the center distance between the two sides of the roller is inconsistent.
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