The printing process of high-strength packaging boxes in China has generally gone through four stages: first, monochrome simple text printing; Next is monochrome halftone image and line printing with more than two colors; Then to today's popular color halftone image overprint; With the continuous development of society, the printing industry of corrugated boxes has gradually moved closer to the high grade, high quality and strong visual effect of colorization, so there has been a large number of high-quality color carton preprint process. As preprint is first printed on corrugated paper, and then compounded and cut on corrugated production line, the color printing level of corrugated boxes has made a qualitative leap. With the popularization of domestic laser plate making industry, it paves the way for intaglio preprint, which is one of the best technology methods to obtain high-quality cartons at home and abroad.
Corrugated boxes usually consist of two processes: printing and molding. Printing process equipment includes offset printing, flexographic printing, gravure printing and silk screen printing; Forming process equipment includes single side machine, cardboard line and slotting/die-cutting/gluing machine. The printing materials can be single sheet paper, web paper and multilayer cardboard. The traditional flexographic direct post printing process uses a cardboard printing machine. Because corrugated cardboard is composed of face paper, core paper and lining paper, and has a hollow structure, the surface of corrugated cardboard is uneven, and the pressure at the valley radius and the valley peak is inconsistent, the phenomenon of washboard will occur. At the same time, the precision of traditional flexographic printing machine is not high, and the printing quality is low, so it is difficult to realize the function of packaging for commodity promotion. Sheet fed offset printing is a traditional preprint method, which is currently the main processing method for high-end color cartons in China. However, the offset preprint method has complex process, multiple processes, low efficiency, and poor environmental protection and safety. During the laminating process, due to the pressure applied on the corrugated core paper and too much water left by the colloid, the flat crush strength, bursting strength, adhesive strength and other technical indicators of the carton are difficult to meet the packaging requirements of high-end goods.