The Influence of Platemaking Process on the Quality of Offset Printing

For traditional offset printing plates, whether or not the process specifications of imposition and printing in the platemaking stage will have a significant impact on the size of the resistance force.

1. Imposition process: Due to the limitation of the format machine's format, most films are to be completed by imposition. If the operation specification is not performed when the imposition is not performed, the phenomenon of film contamination, scraps, etc., and film overlaps will cause the phenomenon of drying out. Versions appear to be false, and network points are not true, resulting in a decrease in print-resistance.

2. Film density: The film density has a great influence on the quality of the printing plate. Some films have a high density and some films have a small density. If the density of the film is not known during the printing, it will easily appear in the normal exposure time. Loss of the local outlets of the edition or the lack of partial text lines, false inaccuracies, etc., will directly lead to a decline in the printing plate's resistance to printing forces.

3. Exposure time and vacuuming issues: In the printing of the PS plate, proper control of the exposure time is an important aspect of effectively increasing the resistance to printing. Excessive exposure time, overexposure, will cause the printing plate outlets to become imaginary, lost or incomplete; exposure time is too short, underexposure, the plate surface photosensitive layer will not be washed during development, causing printing and other dirty trouble. It will also directly affect the size of the resistance force. In addition, during the exposure, attention should be paid to the situation of the stencil vacuuming. If the vacuum evacuation is not true, there will be bubbles between the film and the printing plate or between the film and the glass, so that the dots on the printing plate will be lost or the word will be void when the printing plate is exposed. It is not true, it affects the quality of printing plates, and the resistance to printing forces is reduced.

4. Liquid developer ratio and development time: At present, most of the developer used in the printing plate making industry uses salt, alkali and water in a certain proportion. If the proportion of matching ratio is not good, it will affect the reproduction quality of the printing plate graphic or network. The development time is too long, and the printing plate and the dot part of the printing plate are missing or missing, so that the adhesion of the surface points of the picture and text is reduced. The development time is too short, the surface and the dots of the printing plate are not fully displayed, resulting in the phenomenon of dirty printing, stencil printing, etc., which affects the quality of printed products. In addition, timely application of protective glue after development can effectively protect the PS plate from further oxidation.

5. Baking stage: In order to make the graphic part produce chemical resistance and improve the resistance to printing, baking version is indispensable. When baking, you need to pay attention to the baking temperature setting. If the baking time is too long or too short, it will cause “soft plate” or “peeling”, resulting in brittleness of the oxidation film layer of the printing plate; the mechanical strength and chemical stability of the blank part will be deteriorated, which will affect the printing plate resistance to printing force. Under normal circumstances, baking solution should be coated "thin and uniform", baking time control in 8 ~ 10min, baking temperature control between 200 ~ 230 degrees.

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