The screen printing process is very common in the manufacture of cosmetic packaging materials. The process of screen printing is relatively simple. However, there are many changing factors that affect product quality in the entire screen printing process, which directly affect the final product quality, such as equipment, Improper printing plates, inks, post-processing and operating skills will cause printing failures, and most of them are the result of the cross-influence of multiple factors.
The screen printing process is that the ink passes through part of the mesh of the screen and then leaks onto the substrate. The remaining part of the screen is blocked and the ink cannot penetrate. When printing, the ink is poured on the screen. Without external force, the ink will not leak through the mesh to the substrate. When the squeegee scrapes the ink with a certain pressure and tilt angle, it will transfer through the screen. To the following substrate to realize the copy of the image.
Pre-press material selection
Generally speaking, the screen frames used in screen printing packaging are mostly aluminum alloy frames. Aluminum frames are highly praised by users for their tensile resistance, high strength, good quality, light weight, and convenient use. The size and material of the screen frame play an important role in the quality of the screen.
Select the net
The wire mesh is divided into polyester wire mesh, nylon wire mesh and stainless steel wire mesh, and is divided into multi-wire mesh and monofilament wire mesh. Depends on the accuracy of the print pattern, the quality of the print and the customer's requirements, usually, fine products use monofilament screens.
Stretch the net
The aluminum alloy screen frame is usually stretched by a pneumatic stretcher to ensure the tension of the screen. In order to achieve the best printing quality, the tension of the screen must be uniform. If the tension is too high, the screen will be damaged and cannot be printed; if the tension is too low, the printing quality will be low and the overprinting will be inaccurate. The tension of the screen depends on the screen printing pressure, printing accuracy and the stretch resistance of the screen.
1) First, the stretched screen should be degreased and coarsened to enhance the affinity between the photosensitive glue and the screen.
2) In order to improve the quality of the screen printing, the printing film required for screen printing is required to be positive positive, the photosensitive material is selected according to the substrate, and the thickness of the photosensitive glue depends on the requirements of the printed matter.
3) Exposure time: The exposure time depends on the quality of the film, the number of screen meshes, the thickness of the photosensitive adhesive and the power of the exposure light source. The correct exposure time can improve the quality of the screen printing.
4) Inspection and secondary exposure: After the first exposure of the screen is dried, the quality of the screen printing should be checked and trimmed. After confirming that it is correct, a second exposure should be carried out to enhance the printing endurance of the screen.
5) Substrate: Determine the required substrate according to the requirements of the product and the customer. If it is a substrate provided by the customer, check the material, color, thickness uniformity, surface texture, etc. of the substrate to meet different requirements. Choose the right printing ink.
6) Ink: The physical properties of printing ink mainly include density, fineness, fluidity and light resistance, etc., which have a great influence on the quality and special effects of printed matter. If the density is moderate, the fineness meets the requirements, the fluidity of the formulated ink is ideal, and the light resistance is good, the printed product can achieve the desired effect. Inks are divided into solvent-based inks (natural drying) and UV light-curable inks. According to the requirements of equipment and printing methods, choose the matching ink.