Screen printing consists of five elements, namely screen printing plate, scraping scraper, ink, printing machine and substrate. The basic principle of screen printing is: the use of screen printing plate and graphic part of the screen through the ink, non-graphic part of the basic principle of non-penetration inks for printing. Printing on the screen printing plate at one end of the ink, scraping plates in the screen printing plates on the ink part of a certain pressure, while moving toward the other end of the screen printing plate. The ink in the move by scraping plate from the graphic part of the mesh hole extrusion to the substrate. Due to the viscosity of the ink and imprinted on a certain range, the printing process scraper always with the screen printing plate and substrate line contact, contact line with the scraper moving and moving, due to the screen printing plate and the substrate between a certain gap, so that the printing screen printing plate through its own tension, the reaction of the scraper, which is called resilience. Due to the effect of resilience, so that the screen printing plate and the substrate only mobile line contact, while the other parts of the screen printing plate with the substrate out of the state. Make ink and silk screen break movement, ensure the printing dimensional accuracy and avoid rubbing dirty substrate. When the scraper scratch the entire layout, and the screen printing plate also lifted, and ink to scratch back to the original position. This is a printing trip.