What is the reason for the uneven pressure when the automatic screen printing machine prints?

　　What is the reason for the uneven pressure when the automatic screen printing machine is printing? In screen printing, a suitable and uniform printing pressure is an important guarantee for obtaining high-quality screen printing. If the printing pressure is not uniform, there will be failures in the printed matter.

　　1. The influence of ink viscosity on printing pressure

　　When printing a batch of screen printing products, part of the solvent in the ink will volatilize over time, making the color of the same batch of printed products inconsistent and affecting the uniformity of the printed product. Generally speaking, the ink required for the same batch of printed products needs to be fully prepared at one time, and the viscosity of the ink should be adjusted in time during the printing process to ensure the uniformity of the printed products.

　　2. The influence of screen resilience on the uniformity of printing pressure

　　The printing pressure of screen printing is the result of the joint action of the scraping pressure applied by the squeegee, the resilience generated by the deformation of the screen, and the viscosity of the ink. In screen printing, due to the existence of the screen distance, the screen will be elongated and deformed under the pressure of the squeegee, and the deformation of the screen will be different with the position of the squeegee. The resulting screen resilience is also different. Under the same squeegee pressure, the printing pressure will appear uneven. For flat screen printing plates, the deformation of the screen can be divided into deformation along the travel direction of the squeegee and deformation along the length direction of the squeegee.

　　The resilience of the screen is the component force of the screen tension on the left and right sides of the squeegee in the vertical direction. From the above expression, it can be known that when the squeegee moves on the screen, the deformation of the screen will vary with the position of the squeegee. The resulting screen resilience is also constantly changing. When the squeegee applies a constant squeegee pressure to the screen during the squeegee printing process, the screen printing pressure will vary with the position of the squeegee. Different changes, that is, uneven printing pressure.

　　3. The influence of the screen frame on the uniformity of printing pressure

　　The screen is tightly stretched on the screen frame. Due to the tension of the screen and the asymmetric connection of the screen to the screen frame, the screen frame is deformed, resulting in uneven tension on the screen, which is detrimental to the uniformity of printing pressure. Influence. In the printing process, in order to minimize the deformation of the screen frame after stretching, the screen frame can be pre-deformed. There are two pretreatment methods: one is to make the screen frame into a convex shape according to the strength principle of the arch structure.

　　4. The effect of screen distance on the uniformity of printing pressure

　　The screen distance is determined by the characteristics of screen printing itself. Due to the difference in screen distance, the influence on the uniformity of screen printing pressure is also different. From the formula of screen tension introduced in the previous section, it can be seen that the larger the screen distance, the larger the range of screen deformation, which will increase the range of screen printing pressure along the stroke direction of the scraper, thereby increasing Unevenness of printing pressure. However, if the screen distance is too small, the separation between the screen and the substrate will be unsatisfactory, so that the screen cannot rebound immediately and affect the image clarity. Therefore, in order to improve the uniformity of screen printing pressure, a smaller screen distance should be selected as much as possible while ensuring that the screen can rebound immediately.

　　The reasons for the uneven pressure during the printing of the above automatic screen printing machine are introduced here. The uneven pressure during printing needs to be controlled according to the different products to be printed. The quality of the web print.