The amount of ink transferred to the printing plate when the anilox roll rotates is actually a variable and is affected by many factors. Under normal circumstances, the amount of ink filled in the ink cavity can be transferred to the printing plate in the range of about 70-80%. Even if the stability and dispersion uniformity of the ink itself meet the quality requirements, and the manufacturing precision of the anilox roller is also high, the amount of ink he transfers to the printing plate is also very limited. When the stability of the quality of the printed product is seriously damaged, the fundamental reason is not the performance of the ink itself, nor the accuracy of the anilox roller, but the fact that the ink hole of the anilox roller is blocked by the dry ink during the working process caused. The dry ink at the bottom of the ink hole, especially the water-based ink, is difficult to dissolve in the new ink after drying, unless the dissolution time is very long. Blocking failures will reduce the effective ink transfer of the ink pockets.
There are three basic reasons for its blockage: a. The anilox roller is not cleaned thoroughly when replacing the printed parts; b. The anilox roller is not cleaned for a long time when it stops; c. The drying performance of the ink is too fast. "If a worker wants to do a good job, he must first sharpen his tools." Therefore, in order to maintain the accurate transfer of ink volume, the anilox roller must be properly cleaned.
There are the following 5 cleaning methods:
Chemical solvent scrubbing
Spray the chemical solvent on the surface of the anilox roller, select a suitable fine brush according to the material of the anilox roller (stainless steel brush for ceramic anilox roller, copper wire brush for metal anilox roller), and brush repeatedly with brush. This method is only suitable for cleaning anilox rolls with coarse mesh lines. The advantages are low cost, easy cleaning, and no environmental pollution; the disadvantage is that it cannot penetrate deep into the ink hole for brushing, so the cleaning is not thorough. It is difficult to clean the dirt and ink accumulation at the bottom of the ink hole. Therefore, the ink hole volume cannot be recovered.
Chemical Solvent Immersion Method
All or part of the anilox roller is intruded into the tank of high pH strong corrosive cleaning agent, so that the solvent dissolves, softens and solidifies the ink, and finally washes off the corrosive cleaning liquid and the fully corroded and softened ink with clean water. Although this method It is more effective, but for long-term use, corrosive solvents will penetrate the protective layer and corrode the steel body, which is not conducive to environmental protection.
Ultrasonic cleaning
Immerse the anilox roller in a tank of an ultrasonic cleaning system filled with chemical cleaning solution, the frequency conversion device in the tank sends high-frequency sound waves, the solution vibrates and generates air bubbles, and the dry ink, resin and coating material in the ink cavity vibrate in the solution. Under the combined action of the inward explosive force generated by the directional explosion surface of the bubble, it flows away from the ink hole and with the cleaning liquid. The cleaning time depends on the size of the roller and the ink blockage, generally 0.5-24h. During this time, the anilox roller is subjected to high-frequency ultrasonic vibration for a long time, which will destroy the ceramic layer, and will cause certain damage to the ink layer and the ink cavity of the anilox roller. In addition, this method occupies a large area, has high investment cost, and has a complicated process. Although it has a certain cleaning effect, whether this method is perfect still needs to be tested in practice.
Low pressure spray method
Using sodium bicarbonate and baking soda as cleaning powder, spray and wash the anilox roller under low pressure, the dry ink, resin, coating material, etc. remaining in the ink hole can be thoroughly cleaned, but it should be noted that the spray pressure should not be too high, otherwise It is possible to separate the ceramic soil layer from the anilox roller body, and the general pressure should not exceed 0.1MPa. Since sodium bicarbonate and sodium bicarbonate are a softening cleaning medium, they are easily soluble, non-toxic and harmless, and meet today's global environmental protection requirements. Practice has proved that the cleaning effect of this method is good, and the volume of the ink hole can be restored, and it can be cleaned directly on site, including ink fountain, grease, ink marks, etc. Although this method has only been developed in recent years, it has great potential and is worth promoting.
Plastic bead jet cleaning
The principle is similar to the low-pressure spray cleaning method, but the cleaning powder uses plastic beads. This cleaning method can increase the cleaning speed of the anilox roller by 30%, and can prolong the service life of the anilox roller while improving the quality of the printed product. This method consumes less plastic beads, and there is no discharge of harmful substances and precipitation of chemicals in the cleaning process, which is conducive to environmental protection, high efficiency and safety.
