Packaging film bag printing process principle, composite bag printing belongs to gravure printing, engraving pictures from the outside. Copper or zinc plate is used as the engraved surface, and some concavities can be made by etching, engraving, copper carving or sheet metal. The gravure cylinder brings the ink in the ink fountain to the surface of the printing plate during the rotation process, and scrapes off some blank ink on the surface of the printing plate under the action of the scraper. As the packaging roll film passes between the gravure cylinder and the impression cylinder, the pressure between the volumetric cylinders is used to transfer some of the image and text ink from the gravure cylinder to the receiving primer. As the substrate passes through the drying box, the solvent in the ink evaporates under the action of heat and then goes to the next unit in sequence to complete the multi-color printing. The image and text on the printing plate vary in depth, and therefore the depth of the included ink layer, which transfers to the surface of the print, resulting in a solid and gorgeous printed image and text. Why do some customers say the printing fee is so high. Since the packaging roll film bag is gravure printed, it is completely different from the printing of carton and non-woven bags. This artistic text is engraved on an iron plate and then printed on the machine. A copy fee is required the first time an artwork is made. If the artistic text does not change in the future, no version fee is required.