What about the key points for selecting flour mesh?...

What is the flow of the screen printing process?

1. Screen selection

High-mesh yellow plain woven polyester bolting cloth is a necessary condition for high-precision screen printing. The yellow color is to reduce the diffuse reflection of the exposure light when printing, and the flat woven mesh can form a thin screen to facilitate high-level, low-key reproduction. The same mesh number of mesh has a variety of wire diameters to choose from, it should be easy to break the net. The ratio of the mesh number to the number of film screen lines is 3.5:1. If the number of screen lines is 120 lines/inch, the screen should be 420 mesh.

2. Stretching net

Large-format mechanical stretcher can be used to obtain large tension, prevent tension slack during printing, and screen deformation; the tension of the same set of screens should be consistent; oblique stretch net, mesh warp and weft and frame are 22.5 ° clip The corner helps to reduce the defects of the dot, making the small text and lines perfect. When stretching the net, the initial tensile force should be large, and the net should be pulled once every 1 hour. After 12 hours, the tension of the screen should be measured with a tensiometer. The difference in tension between the parts is not more than 1 N/cm (the tension after the screen printing is 24 to 25 N). /cm). In addition, aluminum alloy or steel mesh frames should be used, and the wooden frame is easily deformed after being immersed in water.

3. Screen production

Take the direct legal plate as an example. After the pretreatment of the screen, the high resolution sensitizer is used, the squeegee surface is coated twice, the printing surface is coated once, and the printing surface is laid down (should be in a dust-free environment); then, at a suitable temperature ( Generally, drying is completed within 35~45°C), the measured tension is not less than 18 N/cm; the thickness of the photosensitive layer is controlled at 10-18 μm, the thickness of the emulsion layer on the printing surface is about 10% of the thickness of the screen, and the Rz value is rough. Degree) is less than the thickness of the emulsion layer. During the coating process, it is very necessary to control the thickness of the screen. When the thickness is too thick, the dark layer cannot be separated, and the highlight is not printed. The rough screen is uneven, which will cause the dot to increase abnormally and the color tone to change. These data can be controlled by instrumental measurements.

The quality of the screen production is the basis for accurate overprinting, stable dot reproduction and good tone-level reproduction. If the customer provides an offset image file, offset proof or color spray proof, the color print reproduction of the screen printing will depend on the operator's knowledge of the screen printing. Before printing, check the bonding between the emulsion surface of the positive film and the screen printing surface, and make the film and the screen have no moiré by rotating the angle, and then fix it with tape.

Sophisticated equipment guarantees us good print quality. To ensure accurate overprinting, it is necessary to choose a high-precision screen printing machine, as well as a plate-lifting screen printing machine, the printing format should not be too large, comprehensive consideration, A3 format is appropriate. The printing material can be selected from transfer paper or low-stretch transfer film, which is pre-shrinked by hot air before printing. The printed materials that have not been printed in one day are wrapped with plastic film to prevent moisture. The hardness of the squeegee is selected from HS80 to 90. Under the premise of not affecting the color tone, the hard rubber squeegee is used as much as possible to form a thin ink layer, which is favorable for the reproduction of the tone level.