What are the common printing methods?

Generally, it can be divided into four categories: relief printing, gravure printing, lithography and stencil printing. The graphic part of the printing plate used in relief printing is convex, including block printing, movable type printing, lead printing, copper-zinc printing, photosensitive resin printing and flexographic printing. Flexographic printing has developed greatly since 1980s, and its printing machine structure and printing substrate are different from general relief printing, so some countries regard flexographic printing as an independent printing category. The graphic part of gravure printing plate is concave, which can be divided into engraving gravure printing, photographic gravure printing and electronic engraving gravure printing. The graphic and non-graphic parts of lithographic printing plate are basically in the same plane, which usually refers to lithography, but in fact lithography (which has been basically eliminated) and lithography (which has been preserved as a unique process) also belong to the category of lithography. Stencil printing is mainly screen printing, that is, a printing plate made of screen, in which the graphic part can pass through ink, but the graphic part cannot pass through ink. Copying mimeograph is also a kind of stencil printing.