How to control the formation of ink layer

Before we can begin to discuss with everyone about how the ink layer is controlled, we should first review some of the problems that we have encountered in the printing industry: 1. When printing a color patch, the color is deep and shallow. 2. Mesh expansion (printed with moire) when screen printing is adjusted. 3, the difference in color changes in batch printing. When these problems are serious, they will affect the progress of production and batch returns, which will inconvenience our normal work. So how to control and prevent these problems from happening is a question worthy of our screen printers. The following are the variables we should understand in printing.

First, analysis of theory through the ink:

There are two methods to analyze the amount of ink transmitted through the screen. One is to calculate the amount of ink through the screen theory, and the other is the actual amount of ink printed. Calculating the theoretical ink penetration has the following formula:

Open hole rate: L

Screen thickness: D

Theoretical ink penetration: M=L×D÷100%

The above formula is only a theoretical calculation of the amount of ink through the screen, once applied to the practice of printing, the data will change, but in direct proportion. Let's look at the following factors:

1. The mesh number of the screen (directly determines the hole width and hole opening rate). The higher the mesh size of the screen, the smaller the hole width and the lower the hole opening rate. For example, the mesh width of the 355 mesh is 31 μm, the opening ratio is 26%, and the theoretical ink penetration is 14.3 cm3/m2. The 305 mesh mesh has a hole width of 45 μm, and the opening rate is 35%. The theoretical ink penetration is 16.3 cm3/m2.

2. The wire diameter of the screen (directly affects the thickness of the wire, the opening rate, and the size of the mesh). It refers to the diameter of the unwoven thread diameter, and the braided thread diameter becomes oval. Will affect the size of the cell. Different screen mesh diameters of the same mesh size will also affect the size of the opening and the opening rate.

For example: 305 mesh wire diameter 31um hole rate is 35%, hole width is 49um, mesh thickness is 49um, the theoretical amount of ink is 17. 2cm3/m2.

305 mesh wire diameter 34um hole rate is 29.6%, hole width is 45um, mesh thickness is 55um, the theoretical amount of ink is 16. 3cm3/m2.

305 mesh screen diameter 40um hole rate is 20. 1%, hole width is 37um, mesh thickness is 65um theoretical ink penetration 13cm3/m2.

3, the thickness of the screen (directly affects the ink layer). We can use the thickness gauge to test the screen thickness of the stretched screen. Since the screens produced by various manufacturers have their own weaving techniques, the curvature of the warp and weft lines is not the same. The greater the degree of bending, the thinner the screen becomes, and vice versa. During the stretching process, due to the influence of external forces, the wire diameter is stretched, which ultimately affects the thickness of the wire mesh.

4, the hole width of the screen (directly affect the amount of ink). We know that the wider the mesh, the greater the amount of ink under the screen. In the process of stretching, the higher the tension, the lower the mesh number, and the wider the mesh opening, the greater the amount of ink penetration.

5, the open hole rate of the screen (directly affect the amount of ink). The so-called open rate refers to the area ratio of the ink-permeated area per unit area of ​​the screen to the total area. For example, for a screen with an aperture ratio of 35%, the ink-permeable portion is 35%, and the portion where the thread is not blocked is 65%. The screen with the higher aperture ratio has a larger amount of ink.

Calculation formula:

Hole width: K

The mesh number is: M

Inches are: Y

Open rate: L=K×M÷Y2×100%

6, the pressure plane of the screen (directly affect the thickness of the network, hole width). More than 355 mesh imported screens are flattened. The flattened mesh will obviously become thinner and the mesh will become smaller. Flattened wire mesh When stretching the net, we look at the following example: When the pressure plane is stretched towards the squeegee, the ink can be saved by 10% to 15%, and the pressure plane can be stretched toward the substrate surface to save ink by 15%. ~25%.

Second, the actual printing through the ink:

1, the tension of the screen (influence the size of the opening, screen mesh, wire diameter, thickness). As the tension increases, the screen's own technical parameters will change accordingly. The mesh number of the screen is affected first, and the higher the tension is, the greater the number of meshes decreases (until plastic deformation of the screen occurs). Next, the width of the mesh will be affected, the mesh will become larger, the wire diameter will become thinner, and the mesh will become thinner. These factors will eventually lead to changes in the amount of ink.

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