Printing Dirty Analysis and Control (I)

At present, there are still many unsatisfactory qualities in the quality of offset printing. Among them, the traces of printed materials still linger. This is one of the common problems of printing and printing companies for many years. Through years of work experience, the author has worked out a set of solutions for controlling the stains on printed products and achieved good results. The results are summarized below for reference by peers.

I. Analysis of Sources of Prints

In order to control the prints of books and journals, it is necessary to make clear the reasons for the formation of the stains, so as to be able to control the stains of the printed materials in a targeted manner. We use the statistical analysis method of fishbone diagram (as shown in Figure 1), we can see that the prints are mainly from the environmental, process, materials and other defects. Specific analysis is as follows:

1. Dirty spots on the film itself

The dirty spots of the film itself mainly come from two situations. One is that many textbooks have a long service life of printed films. During the process of circulation, such as frequent printing, printing, copying, printing, etc. Dirty spots on the film gradually increase, while the dirt in the graphic part is difficult to remove; the other is when the film is due to the developer is not clean or incomplete development, resulting in film stains or yellow.

2. The polyester base of the film is not clean.

3. The environment is not clean, and the dust on the work surface and in the air contaminates the film.

4. The quality of the tape used for the patch is not good, the edges are debonded, the tape marks are dirty, and the film is adsorbed on the PS plate during the process of pumping. When printing, all tape marks are dirty.

5. The print glass is not clean or has air bubbles.

6. The PS coating or substrate is defective. Dirty spots caused by this are generally difficult to remove.

7. The coating on the PS plate is scratched, resulting in dirtiness.

8. The development brush of the PS plate processor has insufficient elasticity and density, and the development is not complete, causing the PS plate to become partially dirty.

9. The baking solution is not evenly coated, and the moisture on the plate after baking is not even, resulting in local dinging.

10. The residual paste on the PS plate has not been removed, and it is easy to get dirty after baking.

11. The water roller and ink roller of the printing press are uneven, and the PS plate is damaged during the printing process, causing the PS plate to be dirty.

12. Under-exposure or under-developed images may also cause dirt on the full version.

13. The platen roller of the plate processor suffers from crystal scratches, which makes the plate roller on the PS plate coating or baking machine dirty.

14. The operator's skill or sense of responsibility is not strong, and the printing plate is not completely dirty.

15. Ink, finger prints, and other stains may occur during printing, assembly, and sample preparation.