8 set printer stroke
First install the substrate, then hold the scraper by hand and move on the surface of the substrate. When the position is appropriate, fix the stop. For curved screen printing machines, the stroke of adjusting the screen movement should exceed the perimeter of the plastic bottle. Proper stroke can save time, increase printing speed, reduce ink discontinuity, and print good dots.
9 select the doctor blade
Generally, the scraper length is about 5 ~ 10mm longer than the image length. The selection of doctor blade involves two aspects: hardness and shape. The scraper with high hardness can carry out very fine graphic and hierarchical printing; The soft scraper is suitable for the substrate with very rough printing surface, and the printing ink layer is also thick. Sharp scraper is often used for surface printing, and scraper with rectangular section is often used for plane printing.
10 select mesh frame
Aluminum products are preferred as screen frame materials, which are relatively light and have high strength. They are suitable for printing hierarchical images, especially for four-color printing. Screen frames with good rigidity must be selected. Many screen frames used in special printing industry belong to non-standard parts, which is due to the strange shapes of substrates for special printing. It is very important that many special screen frames can not be restricted by the screen printer when completing the screen printing task. A very important aspect of selecting the screen frame is to maintain the tension balance in the printed image area.
Mesh frame manufacturing is also an aspect to be considered. The mesh frame should be as hard as possible with good bending and torsion resistance.
11 determine the network distance
Screen distance is the distance between the screen plate and the substrate surface. The size and accuracy of the image will change if the mesh distance is set too large or too small. No matter what tension, too high mesh spacing will cause image expansion. Under large tension, the separation speed of screen and substrate is faster than that of scraper, which will cause the deformation of scraper. Too high net distance also causes serious damage to the screen. Sticky net pulp is not impeccable, it may also fall off due to excessive tension.
Too low screen spacing will make it difficult to separate the screen from the substrate. The separation speed between the screen and the substrate is slower than that of the doctor blade, which will leave mesh marks and cause dirt. The correct mesh spacing should ensure the rapid separation of the screen and the substrate. The selection of screen spacing is related to the screen tension. For high tension screen, a lower screen spacing can be selected, and for low tension screen, a higher screen spacing should be selected. Generally, this data is between 2 ~ 3mm.
Color screen printing should first pay attention to overprint. Only accurate overprint can obtain good prints. To achieve accurate overprint, first, the tension of the screen version shall be basically the same, and the error shall be less than 1n / cm. Measure the tension of each plate with a wire mesh tensiometer and keep it 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 overprint. The four-color printing is the four primary colors. Choosing the one that meets the international standards can avoid the problem of incorrect color.
The establishment of testing standards for color products is conducive to the implementation of institutionalized management and avoid 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. Screen printing has not applied densitometer in controlling color transmission, which is the time to introduce. Otherwise, if you want to compete with other printing processes, the weakness is obvious. Color screen printing is different from simple line text printing. Although experience is important, the mastery of theory is indispensable. We call for fine printing to be comparable to offset printing. It is not our pursuit of unrealistic fantasy. Under the pressure of the market, we have no choice. You may have seen the wild Rhododendron growing in the mountains. She began to enjoy herself in the prosperous metropolis. Because she did not feel at ease in the loneliness of living and dying in the mountains, she opened so brightly, and the screen printing must be more brilliant, because tens of thousands of screen printers are tirelessly exploring.
Post time: Sep-30-2021