Gravure plate failure analysis and troubleshooting: gravure blocking
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In gravure printing, the ink transfer rate is generally 60% to 80%, and 2/5 to 1/5 of the ink will remain in the cells. When the transfer rate of the ink is lowered, the printed image will be imaginary and the writing will be blurred. The lines are unclear, especially in shallow areas. When the blockage is severe, it will also affect normal production. There are mainly the following reasons for blocking:
(1) Reasons for ink
1. The viscosity of the ink is high, the pigment in the ink is unevenly distributed, and the leveling property is not good.
2. The solvent volatilization rate is too fast, or the solvent used is not so soluble in the pigment.
3. The depth of the printing plate dipped in the ink tank is not enough, and the ink is poor.
To solve this problem, it is necessary to appropriately reduce the viscosity of the ink, or to use a slow-drying mixed solvent to reduce the evaporation rate of the solvent. Increase the ink tank position.
(2) Causes and solutions for scraping
1. The scraper is not positioned properly and the scraping point is too far from the stamping point.
2. The blade angle is too large or the blade air pressure is too large.
To solve such blocking problems, it is necessary to adjust the pressure of the scraper and the angle of the scraper so that the scraper is closer to the imprinting point and prevent the hot air in the drying box from leaking out of the direct blowing layout.
(3) Reasons and solutions for printing plates
1. When the printing plate is used, the downtime is too long or the printing plate is not cleaned after the last printing, and the printing plate is dried by the ink, resulting in blocking.
2. The depth of the plate is too deep, and the cleaning at the bottom of the net is not clean, resulting in blocking.
3. The quality of the printed version is not good, and the cell is inverted.
In the event of such problems, the plate should be rechromed.
(4) Other reasons and solutions
If the pressure is too light or the printing speed is fast and the imprinting time is short and the blocking is caused, the pressure should be appropriately increased. The ambient temperature is high or the relative humidity is small, and there is much dust in the air. The static electricity can also cause blockage due to electrostatic dusting. Therefore, maintaining a clean working environment can also reduce the occurrence of blockage.