Seven ways to clean the anilox roll
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In flexographic printing, the mesh of the anilox roller is inevitably blocked by ink, paper coating or paper wool or other dirt, which affects the quality of the printing and the normal use of the anilox roller, and must be cleaned in time. There are 7 methods, but the points to be noted are the same, that is, both the cleaning effect and the damage to the anilox roller are avoided.
First, chemical cleaning method
The ink soaked in the mesh of the anilox roll is dissolved by a caustic soda solution, and then rinsed with a high-pressure water spray. During cleaning, the anilox roller is placed in a closed tank, rotated while being washed with hot alkali, then washed with high-pressure water spray, and finally blown dry with compressed air. In the meantime, the lye and the clean water are separately recovered and filtered. The advantage of this method is that the damage to the anilox roller is small, and the cleaning effect is good, especially for the fine mesh holes of 1000 lines per inch or more.
Second, spray "sand" method
The "sand" particles are sprayed to the anilox roll with compressed air to drive out the dirt such as ink and skin from the cells. “Sand” is not a real grit, but a fine particulate matter with a hardness lower than that of the anilox roll, which is sprayed from the spray gun to the rotating anilox roll by means of compressed air. In operation, the following points should be mastered: the spray gun and the anilox roller should be kept at a certain distance, and vertical, (not deflected, otherwise it is easy to damage the wall of the cell), the moving speed of the spray gun and the rotational speed of the anilox roller should be properly controlled and stable. . The pressure of spraying "sand" should also be controlled properly and constant. If it is light, the cleaning effect will be poor, and it will be easy to damage the anilox roller. Therefore, this method is not suitable for daily use and is only suitable for use in a space.
Third, drying soda powder method
Similar to the second method, but the specially prepared dry soda powder is used as the spray "sand", which is non-toxic and soft and not easy to damage the anilox roller, and has a good decontamination effect. Do not exceed 40 psi of air pressure when spraying. This method can be carried out not only by a dedicated service station, but also within the company, especially on large flexographic printing presses.
Fourth, low temperature method
Dry ice particles made of liquid carbon dioxide are sprayed onto the anilox roll as a spray at a pressure of 80 to 100 psi. The advantage of this method is that it is environmentally friendly. The disadvantage is that the particles of dry ice are usually larger than 0.04 inches, and it is not easy to inject into the cells below 200 lines.
Fifth, spray plastic particle method
This method is often promoted as a method of no wear on the ceramic anilox roll. Similar to other spray methods, there is a closed groove to put the anilox roll into rotation, and the spray gun moves at a certain distance, angle and speed. If polyethylene particles are used, the injection pressure is approximately 60 psi. The plastic particles are soft, but the edges are sharp. When they are sprayed onto the surface of the cells, they will pop out, and the dirt in the cells will be taken out, and then the plastic particles will be separated from the dirt from the air through an air washing chamber. Come, plastic particles can be recycled. The latest developments in this method have been applied to the anilox roll cleaning of 1000 to 1500 lines per inch of YAG laser engraving.
Sixth, ultrasonic cleaning
It is suitable for high-precision laser engraving ceramic anilox roller cleaning. It has a special service station and can be operated by the printing factory. However, the operation of this method should be treated differently depending on the size of the anilox roller, the characteristics of the texture and the design characteristics of the cleaning equipment. For example, the thinner the mesh, the thinner the wall of the cell, and the time of sonication should not be too long.
Due to the characteristics of water-based inks, many ultrasonic cleaners adopt a pre-soaking method to soften the dried ink residue in the cells and then perform ultrasonic treatment. The pre-soaking time often accounts for 80-90% of the entire cleaning time. The pre-soaking liquid is specially formulated, and the pH is high, which helps the soft residue to soften. The level of sound waves during ultrasonic treatment can be reduced and the cleaning effect can be achieved without damaging the cells.
It is important to carefully balance the following factors in ultrasonic cleaning:
The force of ultrasound directly affects the strength of cavitation. The recommendation for its level is very different from the past and present. Because in the past, the narrow anilox roller only had to be partially immersed, but now there is a wide anilox roller, ultrasonic cleaning. It is necessary to completely immerse it in a large groove, so the strength of the ultrasonic wave changes greatly.
The frequency of the ultrasonic waves is inversely proportional to the strength of the holes. As the frequency increases, the bubble size shrinks and the intensity decreases. In general, 40 kHz (40,000 cycles per second) is the lowest level, making the bubble size suitable for cell decontamination, but not absolute, depending on the specific conditions of the device.
The temperature of the cleaning solution has a great influence on the strength of the cavity. The high temperature lowers the viscosity of the cleaning liquid and increases the strength, so that it is advantageous for the cleaning effect. The general temperature should be between 120 and 140 degrees Fahrenheit. Use a specific cleaning solution for a specific device. (such as laser engraved ceramic anilox roller), the temperature should also be mastered according to the cleaning equipment manufacturer recommended.
Cleaning time is also critical, and too long a time can damage the surface coating or cells of the anilox roll. It is best not to exceed 5 minutes when using ultrasonic pre-soaking, but it is not absolute.
Seventh, laser cleaning
The latest method, which uses a special lens laser to shoot the anilox roll, can vaporize residues such as ink, adhesive, wax, silicone, etc. without damaging the anilox roll.