Plate Offset and Troubleshooting

Recently, such a phenomenon appeared in the printing production process: a large-area dot plate with no apparent problem appeared, and one or two spots of sesame grain size were missing after the machine was on the machine. At first, the issue of suspicion was revised, so he reprinted. Strict operation during the printing and revision process ensured that the layout was clean and the outlets were even, but after the machine appeared, there was also a phenomenon that the outlets were out of print, but the location of the edition was different from the previous one. Observed with the magnifying glass off the plate, found that the white point around is very neat, there is no transition between the graphic and blank parts, which ruled out the case may be caused by the exhaust version of the virtual version of the uneven. Re-printing and observing the layout after wiping, there was no occurrence, followed by roasting. After baking, the plate was placed under light and carefully observed with a magnifying glass. As a result, it was found that there was a dot that was missing and was wiped with a wiping cloth. As a result, there has been a phenomenon of missing pages.

In view of the above situation, after careful analysis, it is judged that the possibility of developing solution is large. The developer that we use is prepared by directly dissolving the purchased finished powder in hot water. When the weather is cold or the preparation time is too long, a small amount of particulate sediment will be produced. If it is not completely washed after development, the particles will remain on the plate. Under the condition of heat or external pressure, the particles will continue to play a role in dissolving the graphic part, resulting in plate-off phenomenon. In order to confirm this judgment, we reprinted, fully rinsed after development, wiped the plate evenly with a wet towel, and then glued the plate. Then, using a magnifying glass to carefully observe the layout, there was no situation where the outlets were rendered imaginary. After printing on the machine, everything was good, which also confirmed our judgment.

Analysis of the causes of the failure: First, the developer preparation time is too long, although in the preparation of the developer powder has been fully dissolved, but due to the storage time is too long, or there will be precipitation phenomenon; second, the weather will make the developer precipitation; Third, the operator did not completely follow the production process. After developing, it was directly washed with water, and 2% to 3% of the phosphoric acid solution was not used for the fixing process. As a result, particles remained on the plate after the development, causing the plate-off phenomenon. The method of avoiding this kind of trouble actually is very simple, one is not to use the developer with particle precipitate; The second is to carry on the fixing treatment after developing, and fully wash. After processing according to this method, plate-off phenomena rarely occur.

Author: Lv Yaohua

Reprinted from: Printing Technology