1. Check whether there is dust, garbage and sundries irrelevant to printing around the printing machine, whether the raw and auxiliary materials are sufficient and whether they meet the printing requirements. For the printing of plastic film, the substrate film to be printed is required to meet the following requirements. 2 (1) The surface of the composite bag is smooth and flat, without obvious rigid blocks, black spots, holes and wrinkles. (2) The average thickness error of the substrate film to be printed should be less than 10%. The calculation formula of the average thickness error can be seen from the requirements for dry composite substrate film. (3) The surface tension of the substrate film to be printed should be>4. (4) Know the affinity between the substrate film of the composite bag and the printing ink in advance. 3. Check the quality of the composite bag version roll. Note that the version roll of the next set should be slightly larger than the previous one. For example, the circumference of the second color version roll should be 1% greater than the circumference of the first color version roll. Check the transmission condition of the printing machine. Check whether the feeding, feeding, drying and inking are blocked. 5. The compound bag is used to produce and prepare the ink, and the primary color ink that is the same as the sample color code is selected.