Talk about the imbalance of ink and wash and countermeasures

Keywords: ink balance process monitoring data lithography is the use of oil and water immiscible characteristics, in the printing process to make the surface of the printing plate fountain solution, ink to maintain a relatively balanced, in order to achieve a good copy of the original, to produce high-quality products . In actual production operations, factors such as personnel quality, process, equipment, raw and auxiliary materials, and environmental temperature and humidity will all affect the ink-water balance.
First, the problem of ink imbalance analysis 1. Ink balance performance in the lithographic printing process, fountain solution supply is too small, will cause blank part from the dirty, graphic part of the paste, print scrap; supply is too large, ink Emulsification is severe and normal printing cannot be performed. Specific performance includes:
(1) The paper absorbs the fountain solution excessively during the printing process and curls softly.
(2) Drops of water may appear at the tip of the blanket, and may even accumulate and dribble. Water stains may form on the surface of the print and wet the printing plate cylinder or blanket cylinder pad.
(3) When the print interruption occurs, there is a significant difference in the ink color between the front and back printed sheets.
(4) The ink on the printed sheets is too light, and the amount of ink supply cannot be increased in time.
(5) There are droplets of fountain solution in the ink fountain, and the dampening droplets that have accumulated after the accumulation are also seen in the cutting section of the uniform ink roller.
2. The impact of ink imbalance on printing (1) Incorrect ink transfer: After the ink is over-emulsified, due to too much water and mechanical force, fine water droplets will accumulate on the ink surface, affecting the printability of the ink. . The ink roller is especially deinked by the ink string roller, and the surface of the water roller is dirty and the ink cannot be transferred normally. Excessive moisture can also cause wet peeling (wet off) when the paper is peeled off from the blanket cylinder during multi-color printing. In severe cases, even normal production is not possible.
(2) Printing ink dilutes: In the printing process, excessive moisture causes the ink saturation to decrease, the ink becomes lighter, the color becomes worse, and the color has a sense of oldness. And make the plate at the high-profile office easy to "flower", dark tone at the office easy to "paste", the layout of the surface floating dirty phenomenon.
(3) Decrease of tinting strength of ink: Due to the destruction of the printability of the ink, the tinting strength is reduced, so blindly increasing the amount of ink will cause the dots to be fused and unclear. At the same time, due to the vicious circle of water and ink, more serious ink emulsification occurs.
(4) Slow drying of the imprinting: The imprint of the printed matter is dry, which is the main form of the oxidized conjunctiva of the binder in the ink. When the ink contains a certain amount of acidic aqueous solution, the surface of the imprinted membrane is prolonged and the imprinting is dried slowly, which causes the printed product to become dirty and smeared and affect the production of the postpress process.
(5) Overprinting of printing products is not allowed: Excessive moisture is transferred to the paper by printing plates and blankets, and the paper fibers will be stretched due to excessive moisture absorption. When printing the next color or the back, there will be lotus leaf phenomenon, resulting in inaccurate overprinting, and even accompanied by wrinkles. Due to the unevenness of the paper, the delivery is uneven.
(6) Produce bars: The ink is over-emulsified, and its pigment particles are accumulated on the plate, the blanket and the water roller, so that the pressure and the friction force between them are increased to generate the water bar or the ink bar.
Second, the solution to solve the imbalance of ink and wash 1. Selection of raw and auxiliary materials and printing process monitoring (1) The quality of the printing plate to ensure the solidity of the printing plate graphic and blank basis, the stability of the lipophilic and hydrophilic. Graphic and basic and blank basis and printing plate base have a good adsorption force, uniform and fine grain on the layout, and have a certain resistance to mechanical strength. Before printing, ink and ink pre-adjustment should be carried out according to the area of ​​the layout graphic, field or net pattern. In the printing process, the amount of water can be judged based on the observed gloss of the layout and the condition of the printed product.
(2) Do a good job of matching various types of paper, fountain solution, and printability. The matching relationship can refer to the following table (the values ​​in the table are measured by the samples of the paper commonly used in our factory):

2. The operation should realize dataization, standardization and programming. (1) Realize Sanping: Roller (plate, eraser, embossing) flat, ink roller flat, water roller flat. Strictly according to requirements, according to data, to ensure roller lining, water roller surface level, uniform pressure between each other, the center distance between the three rollers meet the standards, and remain relatively constant in the production process.
(2) To achieve three small: the minimum pressure, to ensure the normal transfer of water, ink and print is appropriate; the minimum amount of water, the printing plate is not premised on the premise, as much as possible to reduce the amount of water; the smallest amount of ink, but To ensure the ink viscosity as much as possible, enhance the ink's water resistance, to ensure that the print meets tone, density, color and other quality requirements. In actual production, the organic combination of the three should be based on specific circumstances.
(3) Specification Wu Qin: Diligently look at the surface moisture, adjust the amount of water in time; diligently stir the ink, improve the ink flowability, and maintain the good transmission performance; diligent ink fountain, so that the ink fountain does not contain dried ink and other sundries; wash the rubber , printing plates, cleaning their surface paper, paper powder and residual ink stains, ink skin, to ensure a good transfer of the blot, to provide a reliable basis for the determination of ink supply; diligent proofs, at any time to draw samples and make proofs for comparison, according to the change Situation, find a new ink balance. The five-working operation should be used as a standardized operation throughout the entire production process.
(4) Dataization: In the state of ink and water balance, the printed ink layer must be thick and consistent in density, and the densitometer is used to monitor the ink density values ​​of the printed products to grasp the changes in the ink balance during the printing process. And to sort out the relevant data under different inks, papers, and different environmental conditions, and finally establish a general data model for each printing press to achieve data management of the printing process.
3. Monitoring of environmental conditions To standardize and regularize the production workshop, environmental temperature and humidity and other conditions must be controlled. The higher the ambient temperature, the lower the humidity, the faster the disperse of the layout water, and the viscosity and fluidity of the ink will change accordingly. Therefore, the production workshop should install air-conditioning as much as possible. In summer, it is appropriate to use a relative humidity of 53% to 67% at 20°C to 30°C, and 18°C ​​to 20°C and 45% to 55% relative humidity in winter.
4. The selection and configuration of equipment should rationalize the use of continuous water supply of alcohol dampening device, which can better meet the monitoring and management requirements for printing quality such as ink-water balance and ink-and-ink transfer in printing production, and should be fully implemented in equipment renewal and improvement. consider. At the same time, other aspects of the printing process should also be considered. For example, according to the specific conditions of the manuscript and the equipment, the printing color sequence that is beneficial to good copying and the balance of ink and ink can be selected; in the design and the plate making of the printed matter, the operator should have a certain understanding of the printing so as to reflect both the design and the design style. To ensure good reproduction, there is a balance between ink and water in printing. (Shanxi People's Printing Factory Li Yan Pan Zhenming) ("Printing Magazine")