Formation of the most popular offset printing dot

2022-08-06
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The formation of offset dot enlargement

dot is the basic unit of ink attachment, which plays a role in transferring the color of adjustment and organization to the increasingly enthusiastic market trend. Dot enlargement refers to the gain of dots printed on the substrate relative to the dots on the color separations

1. Formation of dot enlargement

1 Classification according to point change of printing:

① normal expansion. This kind of printing dot enlargement is allowed, that is to say, the dot is normally enlarged, the density of the center position of the dot is high, and the density of the edge position is low. ② A good product can be detected only when the quality of the ghosting points is good and the accuracy is high. This kind of dot enlargement is not allowed. If dot ghosting occurs during printing, the color rendering effect of dot will be seriously affected. ③ No regular point enlargement. When there is no regular dot expansion, the printing dot does not have a rule, and the dot expands around. At this time, it is easy to have pasted and dirty plates, which will affect the quality of printing products. The point expansion range shall not exceed 15%, 12% and 10%

2. Classified according to the status of point expansion:

① linear expansion refers to the expansion of the edge of the printing point in one direction. Originally, the printing point was square, round, prismatic and chain. Linear expansion refers to the linear expansion of the overall upgrading point of the new material industry in a certain direction. ② The printing point expands to all sides, and the expansion of the point area is generally proportional to the length of the point edge. That is to say, when the area of the point is large, the length of the edge of the point also increases. ③ The increase of density is proportional to the area of printing point, and the increase of density leads to large ink color; If the ink color is large, the dot area will be large

2. There are two cases of point enlargement, mechanical and optical

1 Mechanical dot enlargement: refers to the deformation and enlargement of the ink attached to the metal plate dot by the extrusion of the printing pressure

2. Optical point enlargement: caused by light reflection, when the light reaches the point surface, the surface reflection occurs, and the ink penetrates into the point edge in the paper to form a diffusion halo. This reflection halo forms a tone, and its effect is the same as that of mechanical point enlargement during printing

the enlargement of these two points damages the printed matter to varying degrees and destroys the picture balance. In order to restore the point on the printed matter, it is necessary to control the transfer process of the point (i.e. plate blanket substrate)

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