7. Choose the silkscreen
The wire mesh should have the same number of threads and balanced tension in the warp and weft directions, otherwise it will cause moire and inaccurate overprinting. Mesh parameter indicators should include mesh diameter, mesh number, tension curve and mesh thickness.
(1) Choose a low-mesh screen for rough graphics and text printing, and a high-mesh screen for fine graphics and layer printing;
(2) The selection of the screen mesh number should match the number of screen lines of the printing soft plate. Generally, 4 times the number of screen lines of the printing film is used as the screen mesh number;
(3) For UV, considering the curing effect, the mesh count should not be too low.
(4) Dyeing screen is preferred for fine graphic printing and layer printing, and the resolution of dyed screen is much higher than that of white screen.
(5) Selecting the mesh calculator can help you obtain data support and determine the relationship between the static mesh number and the dynamic mesh number.
8. Set the press travel
First install the substrate, then hold the scraper by hand to move on the surface of the substrate, and fix the stopper when the position is appropriate. For curved screen printers, the stroke to adjust the screen movement should exceed the circumference of the plastic bottle. Proper itinerary can save time,
Increasing the printing speed also reduces the incoherent phenomenon of ink supply, and can print good dots.
9. Choose a squeegee
Generally, the length of the scraper is about 5~10mm longer than the length of the image. The choice of squeegee involves both hardness and shape. The higher hardness squeegee can be used for very fine graphics and layer printing; the softer squeegee is suitable for printing with very rough printing surface
material, the printing ink layer is also relatively thick. Curved printing often uses a sharp squeegee, and flat printing often chooses a rectangular cross-section squeegee.
10. Select the frame
The screen frame material is preferably made of aluminum products. It is lighter and has high strength. It is suitable for printing layered images, especially for four-color printing. A screen frame with good rigidity must be selected. Many screen frames used in the special printing industry are non-standard parts. , This is caused by the strange shapes of the substrates for special printing. It is very important for many special screen frames to be able to perform screen printing tasks without the constraints of the screen printing machine. A very important aspect of selecting a screen frame is to be able to maintain a balanced tension in the printed image area.
The manufacture of the screen frame is also an aspect to be considered. The screen frame should be as hard as possible, with good resistance to bending and twisting.
11. Determine the mesh distance
Screen distance is the distance between the screen and the surface of the substrate. Setting the screen spacing too large or too small will change the size and accuracy of the image.
At any tension, too high a mesh distance will cause the image to expand. Under larger tension, the separation speed of the screen and the substrate is faster than the running speed of the squeegee, which will cause the deformation of the squeegee. Excessive mesh distance is also very damaging to the wire mesh. The sticky web is not infallible, and it can also fall off due to excessive tension.
Too low screen distance will cause the screen and the substrate to be difficult to separate. The separation speed of the screen and the substrate is slower than that of the squeegee, which will leave screen marks and cause smearing. The correct screen distance should ensure the rapid separation of the screen and the substrate. The selection of the mesh spacing is related to the mesh tension. A lower mesh spacing can be selected for high-tension meshes, and a higher mesh spacing should be selected for low-tension meshes. Generally, this data is between 2 and 3 mm.
12. Printing
Color screen printing must first pay attention to the problem of overprinting, and only accurate overprinting can obtain good prints. To achieve accurate overprinting, first of all, the tension of the screen plate should be basically the same, and the error should be less than 1N/cm. Use a screen tensiometer to measure the tension of each plate, which should be kept at 18N/cm. The uniformity of the positioning device is very important. Each substrate must have the same position when entering the printing, otherwise it will cause inaccurate overprinting. The four-color printing is the four primary colors, and choosing the one that meets the international standard can avoid the problem of color inaccuracy.
Establishing testing standards for color products is conducive to implementing institutionalized management and avoiding disputes between manufacturers and customers. It should be said that very little work has been carried out in the special printing industry. I believe this situation will change one day.
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