If the screen is a silk screen “standard templateâ€, the screen is the skeleton of this standard template. The quality of the screen quality directly affects the screen printing effect. As a screen printing worker, understanding the technical parameters of the screen and their effect on the application performance has a great guiding significance for selecting a reasonable screen, ensuring the printing of high quality products and controlling the cost.
First, screen technology parameter classification
The technical parameters of the screen can be divided into three categories according to the performance characteristics. The first category is the specification index parameters, such as the mesh number, open hole rate, etc., which are dominant technical parameters; the second category is the physical performance parameters, such as the maximum tension, which need to be reflected through the stretch net or use process; the third category is The use of performance parameters, such as ink penetration, must be reflected by actual printing and is a recessive technical parameter.
According to the relevance classification, the technical parameters of the screen can be divided into two categories: basic technical parameters and related technical parameters. The basic technical parameters are the parameters that determine the performance of the screen, and the associated technical parameters vary with the basic technical parameters.
SPECIFICATIONS AND PARAMETERS PARAMETER SCREEN PRINTER SELECTIONS The screen is the first concern, which determines the basic characteristics of the screen; the physical performance parameters are the index most concerned by plate making workers; the use of performance parameters is of less concern to everyone. The three types of technical parameters are closely related to each other.
What needs to be emphasized here is that we are paying attention to the technical indicators of the wire mesh. We can't just care about “how muchâ€, but we should also pay more attention to the “tolerances†of the indicators. This “tolerance†is precisely the key to the impact of screen quality on print quality.
Second, the two major specifications of screen parameters - mesh number and wire diameter
1. Mesh number and wire diameter: The number of meshes and wire diameter are the main parameters of the two main specifications of the screen.
The number of meshes refers to the number of meshes in a certain size, and is usually calculated in units of 1 cm or 1 in. For example, 300 mesh refers to 300 meshes within 1 inch. Our national standard method DPPl00 refers to 100 meshes within 1 cm.
The wire diameter refers to the diameter of the raw material, in micrometers (μm). For example, 300/120 to 34 refers to a mesh of 300 mesh (120 mesh per centimeter) per inch and a wire diameter of 34 microns. It should be pointed out that 34 micron is the diameter of the raw silk, and after the processing steps such as weaving and post-processing, the diameter of the wire will change.
The mesh size and the wire diameter determine the mesh size (aperture) and the open area ratio.
Formula one: 10000/Me=D+M
Me - mesh per centimeter
D——wire diameter, unit μm
M - aperture, unit μm
Such as: 100 mesh / cm, wire diameter 34μm plain woven wire mesh, aperture 66μm; 100 mesh / cm, 39μm plain weave mesh, aperture 61μm.
2, wire diameter, aperture and screen can be the smallest dot: screen printing is often used dot printing, the screen can be expressed by the smallest dot diameter and diameter determined by the hole, the following is a summary of the empirical formula.
Formula two: d=√2(2D+M)
d - diameter of the smallest dot, unit μm
M - aperture, unit μm
D——wire diameter, unit μm
Calculation example: 100 mesh/cm, 34μm diameter wire mesh, the smallest dot that can be expressed is 189μm; 100 mesh/cm, 39μm mesh screen, the smallest dot that can be expressed is 197μm. Table 2 shows some of the specifications of commonly used screens.
Table 2 commonly used wire mesh specifications
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3. Uniformity of mesh pore size: The formula 1 calculates the theoretical value of the mesh aperture, but the mesh is a textile product. Affected by the processing technology, the aperture of the mesh does not completely meet the design requirements, and there are deviations in the indicators. The use of deviations for the use of the user, especially at the point of printing, causes great trouble. We can use formula 2 to calculate that the minimum dot diameter at 100 mesh/cm and wire diameter of 34μm at 25% of screen diameter deviation increases from 189μm to 213μm, which is equivalent to the expressive force of screen mesh of 90 mesh/cm and 39μm.
There are many kinds of uneven mesh aperture, one is the horizontal band-like uneven irregularity; one is a line of regular irregularities, may be the direction of the warp may also be latitude; there is a longitudinal gradient The unevenness. The greatest impact on the user is the horizontal band-like irregularity, and it is also the most common aperture unevenness in domestic low-price screen products. We have tested the screen products on the market and found that some screen meshes have an aperture deviation of more than 50%. Such screens have also had a significant impact on the printing of color patches. Dot printing cannot be used at all.
By the way, because the fiber raw material is deformed during processing, the screen mesh is not a standard square, and the four sides of the mesh are not straight lines but arcs; the actual aperture and opening area of ​​the mesh are smaller than the theoretical value. . The worse the quality of the screen, the more obvious the four sides of the mesh arc, the greater the difference between the actual value and the theoretical value of the aperture, opening and hole.
First, screen technology parameter classification
The technical parameters of the screen can be divided into three categories according to the performance characteristics. The first category is the specification index parameters, such as the mesh number, open hole rate, etc., which are dominant technical parameters; the second category is the physical performance parameters, such as the maximum tension, which need to be reflected through the stretch net or use process; the third category is The use of performance parameters, such as ink penetration, must be reflected by actual printing and is a recessive technical parameter.
According to the relevance classification, the technical parameters of the screen can be divided into two categories: basic technical parameters and related technical parameters. The basic technical parameters are the parameters that determine the performance of the screen, and the associated technical parameters vary with the basic technical parameters.
SPECIFICATIONS AND PARAMETERS PARAMETER SCREEN PRINTER SELECTIONS The screen is the first concern, which determines the basic characteristics of the screen; the physical performance parameters are the index most concerned by plate making workers; the use of performance parameters is of less concern to everyone. The three types of technical parameters are closely related to each other.
What needs to be emphasized here is that we are paying attention to the technical indicators of the wire mesh. We can't just care about “how muchâ€, but we should also pay more attention to the “tolerances†of the indicators. This “tolerance†is precisely the key to the impact of screen quality on print quality.
Second, the two major specifications of screen parameters - mesh number and wire diameter
1. Mesh number and wire diameter: The number of meshes and wire diameter are the main parameters of the two main specifications of the screen.
The number of meshes refers to the number of meshes in a certain size, and is usually calculated in units of 1 cm or 1 in. For example, 300 mesh refers to 300 meshes within 1 inch. Our national standard method DPPl00 refers to 100 meshes within 1 cm.
The wire diameter refers to the diameter of the raw material, in micrometers (μm). For example, 300/120 to 34 refers to a mesh of 300 mesh (120 mesh per centimeter) per inch and a wire diameter of 34 microns. It should be pointed out that 34 micron is the diameter of the raw silk, and after the processing steps such as weaving and post-processing, the diameter of the wire will change.
The mesh size and the wire diameter determine the mesh size (aperture) and the open area ratio.
Formula one: 10000/Me=D+M
Me - mesh per centimeter
D——wire diameter, unit μm
M - aperture, unit μm
Such as: 100 mesh / cm, wire diameter 34μm plain woven wire mesh, aperture 66μm; 100 mesh / cm, 39μm plain weave mesh, aperture 61μm.
2, wire diameter, aperture and screen can be the smallest dot: screen printing is often used dot printing, the screen can be expressed by the smallest dot diameter and diameter determined by the hole, the following is a summary of the empirical formula.
Formula two: d=√2(2D+M)
d - diameter of the smallest dot, unit μm
M - aperture, unit μm
D——wire diameter, unit μm
Calculation example: 100 mesh/cm, 34μm diameter wire mesh, the smallest dot that can be expressed is 189μm; 100 mesh/cm, 39μm mesh screen, the smallest dot that can be expressed is 197μm. Table 2 shows some of the specifications of commonly used screens.
Table 2 commonly used wire mesh specifications
Click here for all news photos
3. Uniformity of mesh pore size: The formula 1 calculates the theoretical value of the mesh aperture, but the mesh is a textile product. Affected by the processing technology, the aperture of the mesh does not completely meet the design requirements, and there are deviations in the indicators. The use of deviations for the use of the user, especially at the point of printing, causes great trouble. We can use formula 2 to calculate that the minimum dot diameter at 100 mesh/cm and wire diameter of 34μm at 25% of screen diameter deviation increases from 189μm to 213μm, which is equivalent to the expressive force of screen mesh of 90 mesh/cm and 39μm.
There are many kinds of uneven mesh aperture, one is the horizontal band-like uneven irregularity; one is a line of regular irregularities, may be the direction of the warp may also be latitude; there is a longitudinal gradient The unevenness. The greatest impact on the user is the horizontal band-like irregularity, and it is also the most common aperture unevenness in domestic low-price screen products. We have tested the screen products on the market and found that some screen meshes have an aperture deviation of more than 50%. Such screens have also had a significant impact on the printing of color patches. Dot printing cannot be used at all.
By the way, because the fiber raw material is deformed during processing, the screen mesh is not a standard square, and the four sides of the mesh are not straight lines but arcs; the actual aperture and opening area of ​​the mesh are smaller than the theoretical value. . The worse the quality of the screen, the more obvious the four sides of the mesh arc, the greater the difference between the actual value and the theoretical value of the aperture, opening and hole.
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