Offset printing and its forming classification and production

Dots are the basic unit of ink adhesion and play a role in transferring and organizing colors. Dot enlargement refers to the dot gain on dots printed on the substrate relative to the dots on the color separation sheet.

First, the formation of outlet expansion

1. According to the printing outlets change classification:

1 Normal expansion. This kind of printed dot enlargement is allowed, which means that the dots are expanding normally, with high density in the center of the dots and low density of edge locations. 2 ghosting outlets. This kind of printing dot enlargement is not allowed. If there are dot ghosts during printing, the dot color effect will be seriously affected. 3 There are no regular network expansions. When there are no regular dot gains, there is no rule in the printed dots, and the dots will expand around. At this time, stencils and dirty prints will appear, which will affect the quality of printed products. The network expansion scope does not exceed 15%, 12%, and 10%.

2. According to the status of the expanded network:

1 Linear enlargement means that the edge of the printing dot has a direction of expansion. Originally, the printing dot is a square, a circle, a prism, and a chain. The linear expansion means that the dot expands linearly toward a certain aspect. 2 The printed dots are expanded in all directions. The enlargement of the dot area is generally proportional to the length of the edge of the dot. In other words, the dot area is large, and the length of the edge of the dot also increases at this time. 3 The increase in density is proportional to the area of ​​the printing dot, the density increases, the ink color is large, the ink color is large, and the dot area is large.

Second, there are two kinds of mechanical and optical network points to expand the production of 1. Mechanical network expansion: refers to the ink attached to the metal version of the printing point of the press pressure and deformation and expansion.

2. Optical dot enlargement: Due to light reflection, when the light reaches the surface of the dot, surface reflection occurs, and the ink penetrates into the edge of the dot in the paper, forming a diffusion vignette. This kind of reflection vignette forms a tone. The effect is the same as the mechanical dot enlargement during printing.

These two types of dot-extensions have a detrimental effect on printed materials to varying degrees and destroy the balance of the picture. In order to make a true reduction of the outlets in the printed matter, it is necessary to control the delivery process of the outlets (ie, printing plates—blankets—substrates).

Author: Tangying Lian Source: "Guangdong printing"