Drum screen printing process problems and solutions

Screen printing plate making is the basis of screen printing. If the plate making quality is not good, it is difficult to print a good quality product. The failures in printing are often related to the improper selection of materials in plate making process technology and plate making. Therefore, if you want to make a good quality screen printing plate, you must correctly master the plate making technology according to the requirements of the plate making process, and strictly select plate making materials for plate making. The issues involved in the platemaking work include: how to correctly use the materials used in plate making, such as screens, frames, and photosensitive materials, and how to master the bottom plate making, stretching, coating, printing, developing, and light source.

(a) Screen

The screen is the skeleton of the screen, and it is the substrate that supports the photosensitive film. The commonly used wire mesh screen printing for steel drums is monofilament nylon mesh, thin nylon mesh, and stainless steel mesh.

1, nylon mesh

It is a nylon monofilament woven, heat-treated and dimensionally stable after weaving. Plain weave can reach 380 mesh and twill weave is larger than 330 mesh. Nylon mesh has the following characteristics:

(1) The nylon mesh has a smooth surface and good ink permeability, and can use inks with large viscosity and large particles, so that a fine print pattern can be obtained;

(2) Use fine mesh woven mesh nets, suitable for very fine line drawing patterns and dot printing;

(3) Large elasticity, appropriate flexibility, good adaptability to the surface of steel drum, suitable for printing curved surface of steel drum;

(4) The tensile strength, nodule fastness, elasticity and friction resistance are good, and the service life is long;

(5) Good resistance to acids, chemicals, and organic solvents. Recycling is easy, especially for alkalis.

Use nylon mesh should pay attention to the following points:

(1) Compared with polyester silk and silkworm silk screens, nylon silk screens have high elongation. In order not to cause a printing failure, it is necessary to increase the tension of the stretching net, and at this time, the contraction force also becomes large. Therefore, it is required to use a strong frame and a stretching machine.

(2) Because of its low heat resistance, if the mesh is fixed to the frame by the hot melt method, the operation is difficult;

(3) It is not resistant to erosion by strong acids, phenols, cresols, formic acid, etc.;

(4) Poor light fastness, easy to degrade under ultraviolet light, avoid light when storing.

2, polyester mesh

Polyester mesh has the following features:

(1) It has small elongation and strong elasticity when it is under tension, and single-line screen is suitable for high-precision printing;

(2) Tensile strength, structural strength, resilience, and print resistance are all good;

(3) It has sufficient chemical resistance, especially acid resistance and organic solvent resistance, and can be recycled and utilized like nylon.

(4) Low hygroscopicity, hardly affected by humidity;

(5) Heat resistance is higher than that of nylon, and is less affected by ultraviolet rays than nylon.

Polyester mesh should pay attention to the following points:

(1) It needs more stretched net tension than nylon net, and it requires stronger frame, stretcher and firmer bonding method;

(2) Due to the hydrophobicity of polyester, it is difficult to adhere to the plate, and care must be taken to wash and degrease the plate before plate making.

(3) The ink is poorer than nylon, and is not resistant to alkali corrosion.

3, stainless steel wire mesh

Stainless steel wire mesh has the following characteristics:

(1) excellent plane stability, stable dimensionality of the produced graphics, suitable for printing high-precision steel drum products;

(2) excellent ink passability;

(3) Good alkali resistance and tensile strength, excellent chemical resistance;

(4) Strong heat resistance, suitable for the printing of hot melt printing materials.

The disadvantages of stainless steel wire mesh are:

(1) susceptible to damage due to external forces;

(2) In the printing process, the mesh tends to be loose due to pressure, which affects the resistance to the printing force;

(3) The price is high and the cost is high.

The thickness of the screen should be compatible with the fineness of the pattern on the surface of the drum. The rough pattern can be used with a coarse mesh below 200 meshes, the general pattern is a screen with 200-300 meshes, and the fine pattern is a fine mesh with a mesh size of 300 mesh or more.

Nylon mesh, polyester mesh and stainless steel mesh are commonly used screen printing materials. Nylon mesh has good resilience, good ink permeability, less static electricity than polyester mesh, good abrasion resistance, moderate cost, and is generally The preferred screen for drum printing. However, due to the high elongation of nylon mesh, it is not suitable for printing high-precision patterns. For screen printing, such as multicolor printing, polyester screens are preferred; when printing patterns require particularly high precision, stainless steel screens should be used. Because stainless steel screens have major drawbacks of poor flexibility and high price, they are generally used less frequently in screen printing of steel drums. (to be continued)