1. Letterpress printing; 2. Gravure printing; 3. Lithographic printing; 4. Screen printing; 5. Photocopying; 6. Thermal transfer printing; 7. Electrostatic copying; 8. Inkjet printing. Among them, the first three printing methods are more commonly used, and the printed matter produced by the first three methods occupies a large part of the printed matter produced each year. Below, for each printing process, a brief description is given. Letterpress printing When ink is applied to a raised surface and a sheet of paper is pressed against the inked surface, the ink is transfer to the paper. The method of printing using this principle is called letterpress printing. Letterpress printing is the oldest printing method. There are now many different types of printing plates used on different types of printing presses to print colorful and varied products, including newspapers, books and magazines. Vacuum packaging bags, tea packaging bags Gravure printing Letterpress printing transfers ink from a raised surface to the paper, while the gravure printing process is just the opposite. In the gravure printing process, the ink is transfer from a recessed surface to the paper, and the part of the graphic on the gravure plate is below or sinks into the surface of the printing plate. During the printing process, first apply ink on the entire surface of the printing plate, and then wipe the layout clean, so that ink is left on the concave part of the printing plate, and then the paper is pressed on the printing plate, and the ink is transfer to the paper. superior. [Packaging bag printing]