First, discuss the relationship between the minimum dot diameter D and the mesh diameter d and the number of meshes M.
Since the screen dots are disturbed by the wire diameter, the small dots are easily blocked by the mesh and lost, and the degree of loss is related to the position of the dots on the screen.
As shown in Figure 2 on the following page, the mesh diameter is d and the aperture is m. The circle with a diameter of Dmin shown in the figure contains four mesh nodes 1, 2, 3, and 4 of the wire mesh. Using Dmin as the minimum mesh point diameter can obtain a more complete imprint.
Table 3 The data calculated by formula (2)
Number of screens
5% tone dot diameter (μm) 10% tone dot diameter (μm) 20% tone dot diameter (μm) Line / cm wire / inch 30 76 84 119 168 34 86 74 105 148 40 63 63 89 126 48 53 53 74 105 54 47 47 66 93 60 42 42 59 84Available from the icon:
Due to the following relationship between mesh number, mesh diameter, and aperture:
m = 1 / M—d
Substituting into (3) can get:
The data in Table 4 can be calculated according to equation (4) for comparison and selection.
When selecting the appropriate mesh screen number, it is necessary to comprehensively consider Table 3 and Table 4 before making a choice.
2.3 Selection of wire mesh series
The order of the wire mesh refers to the fineness of the wire mesh. For the mesh with the same mesh number, according to the thickness of the mesh, it is divided into the following four different levels: S fine grade, M medium fine grade, T medium coarse grade, HD coarse grade, namely S, M, T, HD Four series. The diameter of the mesh is usually expressed in microns. After selecting a certain mesh, the following factors should be considered when selecting the grade:
a. The smaller the mesh diameter is, the larger the relative opening area is, and the more suitable it is for fine-level replication;
b. The smaller the mesh diameter, the worse the corrosion resistance of the corrosive cleaning agent, and the worse the wear resistance of the ink and the doctor blade;
c. The larger the screen diameter, the higher the screen durability.
In general, in addition to considering the above factors, the choice of screen should also consider aspects such as its plate-making method, ink type, membrane life, production cost requirements, etc. After comprehensive consideration, the correct choice can be made to achieve the best printing effect and economic benefit.
Table 4 Calculation list of minimum dot diameter
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