Factors affecting the dot reduction

The influencing factors and solutions for the reduction of printing technology network points are the basis for the reproduction and color reproduction of printed materials, and are the true reflection of the adjustments, levels, and color reproduction of printed materials. The quality of the outlets will directly determine the quality of the printed matter, so controlling the quality of outlets is of great significance.

The reduction of outlets is a major factor affecting the reproduction of outlets and affecting the quality of printing. The maximum density, exposure, and development conditions of the film during printing, as well as the friction during printing, the viscosity of the ink, and the yield value are the main factors that cause the dot to shrink.

1. Effect of maximum film density

Shaiban is the process of transferring the graphic on the film to the PS plate by bringing the film and PS plate together. In general, the field density of the film used for printing is greater than 3.5, preferably about 4.2; at the same time, the dot type of the dot is better, that is, the edge around the dot is required to be clear, and the boundary with the blank is clear. If the density in the field is too low, the small dots of the image will easily shrink or even be lost when the printing is in progress. Fine text will have broken lines and other phenomena. If the edges of the dots on the film are blurred, the dot on the PS plate will randomly change as the exposure and development conditions change, and the dot may increase or decrease.

2. The impact of exposure

Nowadays, stencil printers generally use the light emitted by a UV lamp as the exposure light source, so that the light is not parallel but scattered. The scattered light is reflected by the film and reflected on the surface of the PS plate to reach the lower part of the film web site. The edge, then the edge of the corresponding dot formed on the plate is in a half-exposure state. The light directly under the UV lamp is relatively parallel, and the half-exposing degree of the edge of the dot is lighter, while the phenomenon of the small dot around is more serious. When developing, dot area will be reduced and even some small dots will be lost. For a different PS version to use the appropriate exposure, if the exposure is too large, even if the normal development conditions, dot area will be reduced.

3. Effect of developing conditions

The developer concentration is too large or the development time is too long. Even under normal exposure, the developer will excessively corrode the PS plate. This will often dissolve or even completely lose the small dots of the picture and text, and the printing plate will also resist the printing force. decline. In general, 5% or less of the outlets are easy to lose, and 40% of the outlets have smaller outlets. If the PS version of the body is overexposed, the concentration of the developer is too large and the development time is too long, which will also cause the dot to shrink.

4. Effect of friction during printing

In order to prevent the blank part of the printing plate from absorbing ink when printing, it is required to moisten the printing plate with fountain solution before inking. During the high-speed operation of the printing press, the surface of the printing plate is rubbed by the water roller and the rubber roller. Friction wears the sand around the dot, and the dampening solution immerses in it, forming a hydrophilic, oil-repellent film. For the high-profile part of the printing plate graphic, the area coverage of its own dot is smaller, and the hydrophilic area is larger than the lipophilic area, which is conducive to the expansion of the fountain solution, and the formation of a hydrophilic and oil-repellent film due to abrasive wear. Preventing the normal spread of ink will inevitably cause the dot to shrink.

5. Effect of ink viscosity and yield value

The viscosity of the ink is too large, and the yield value is too high. It is easy to cause the phenomenon that the ink is not easy to flow, the ink is too short, and it is not easy to spread on the PS plate. Even if it is spread under the effect of printing pressure, the ink on the printing plate dot will also be due to viscosity. Excessively high and shrinking to the center, this will also cause the network to shrink.

In view of the above situations, if the highest density of the film is not enough to cause the reduction of the dots, only a set of film with the right density will be re-exported to solve the problem.

In the case of a suitable density of the film, the factors that cause the dot to be reduced during the plate making process are mainly the amount of exposure and development conditions.

This can be solved by using signal strip tracking management. During the printing, the grey ladder rule is tightly combined with the PS plate and then exposed. After the development, by observing the reproduction of the steps, it is possible to check whether the exposure amount, the developer concentration, and the development speed are appropriate, and then adjust them according to the actual situation, so as to achieve the purpose of avoiding dot reduction.
For the reduction of dots due to friction during the printing process, the printing pressure can be reduced as much as possible in order to ensure the ink transfer and the dot reproduction to be good, thereby avoiding the reduction of the dot due to the abrasion of the printing plate due to friction.

In short, the quality of outlets has a direct impact on the reproduction and reproduction of prints. Therefore, it must be controlled throughout the entire printing process to avoid the reduction of outlets or to minimize the reduction of outlets. The influencing factors and solutions for the reduction of printing technology network points are the basis for the reproduction and color reproduction of printed materials, and are the true reflection of the adjustments, levels, and color reproduction of printed materials. The quality of the outlets will directly determine the quality of the printed matter, so controlling the quality of outlets is of great significance.