Taking the commonly used Flat Screen Printing Machine as an example, the working principle of the flat screen printing machine can be described as follows: power is transmitted through a transmission mechanism, so that the ink scraping plate squeezes ink and the screen printing plate in motion, so that the screen printing plate and the printing material form an impression line; as the screen has tension N1 and N2, a force F2 is generated on the ink scraping plate, the resilience force causes the screen printing plate not to contact the printing material except the impression line, and the ink leaks onto the printing material from the moving impression line through the mesh under the squeezing force F1 of the ink scraping plate.

In the printing process, the screen printing plate and the ink scraping plate move relative to each other, and the pressing force F1 and the resilience force F2 also move synchronously. Under the resilience force, the screen returns in time to disengage from the printing stock, so as to avoid smearing marks. That is, the screen is constantly deformed and rebounded during the printing process. After completing one-way printing, the ink scraping plate is separated from the printing stock together with the screen printing plate, and ink is returned back at the same time, thus completing a printing cycle. After ink return, the distance between the upper surface of the substrate and the reverse side of the screen printing plate is called the same plate distance or screen distance, which should generally be 2 ~ 5 mm. During manual printing, the skill and proficiency of the operators directly affect the formation of the nip.

In practice, silk screen printing workers have accumulated a lot of valuable experience, which can be summarized into six points, namely, to ensure the straightness, uniform speed, equiangular, pressure equalization, centering and vertical edge of the ink scraping plate. In other words, when printing, the ink scraping plate should move in a straight line and not shake left and right. Not slow before and fast after, fast before and slow after or slow and fast; The inclination angle of the ink board should be kept unchanged, and special attention should be paid to overcome the common fault of gradually increasing inclination angle. The printing pressure should be kept uniform. Keeping the distance between the ink scraping plate and both sides of the inner side of the screen frame equal; Until the ink board is perpendicular to the frame.