V. Dark ink dots in the field version
The dark ink spots in the field version are rarely met on new flexo presses. Often the machine has been used for 3-4 years, and this problem has gradually emerged. The author came into contact with this problem after using a German flexo press for 3 years. In the field printing, we found small dark ink dots in the pattern, such as dark blue (blue+violet) version. In the even dark blue layout, there are many irregular ink dots with a diameter of 0.5mm or less. The color is deeper than the normal deep blue and observed with a magnifying glass. It is impossible to distinguish the boundary between dark ink dots and other uniform ink colors. At first, it was suspected that the temperature was too low to cause the ink resin to freeze. (The ink does contain some polyamide resin as well.) The paint was layered with the resin, and the ink was insulated before use and was stirred with a pneumatic mixer before use. Then suspect that the impurities in the ink, filtered with a multilayer filter, but also not effective. Later, it was discovered that when the speed of the vehicle slowed down, the dark-colored ink spots were significantly improved, and when the viscosity of the ink was high, the effect of the dark-colored ink dots was noticeable, and when the viscosity was low, the ink-dried ink dots showed a better improvement. In addition, the entire ink tank was The probability of dark ink spots near the ink tube is low, and the probability of dark ink spots near the ink return tube is high. The appearance of these phenomena prompted us to make a more comprehensive inspection of equipment and materials, and An analysis of the dark ink spots produced in the field version was obtained.
1. . Anilox roller beating. The anilox roller equipped with the new machine, the radial runout error is generally about 10-15 u, not too much, but after 3-4 years, due to wear, this parameter will appear error. After the anilox roller generates a radial runout, the blade cannot press it, causing jitter, resulting in dark ink dots of the same color.
2. When a flexo printer prints at a high speed, ink with a certain viscosity will form an impact force on the blade. The higher the speed, the greater the viscosity of the ink, and the greater the impact force. When the blade cannot withstand this impact, it will inevitably produce. Dark ink spots. In the fault phenomenon, the dark ink dots near the ink tube appear less and the dark ink dots near the ink return tube appear much more. It is precisely because of the ink pump that the ink flow at the ink tube is good and the viscosity is high. Low, and there are always some dead spots at the ink return tube, poor fluidity, and high ink viscosity.
3. Scraper configuration. The commonly used steel scraper with Swedish blue steel as the base material is about 0.15mm thick and has a hardness of 580HV. The commonly used cutter head is a round head, and the tip of a certain side is a certain slope and the tip is 1/2 blade thick. The function of scraper and scraper is to scrape the excess ink on the anilox roller. When the anilox roller beats, if the scraper is too soft, the excess ink on the anilox roller cannot be scraped. If the scraper is too hard, it can't cling. The anilox roller moves together. Therefore, even if the blade is pressed tightly against the anilox roller, the relationship between the anilox roller and the doctor blade, which has a certain error, is still fluent. It is precisely these dark ink dots in the field printing. If the ink is removed from the printing plate, a darker ink dot is formed than the normal ink color saturation.
Based on this, the dark ink dot solutions in field printing are:
1. Repair and solve the mechanical error, so that the anilox roller beating control within the proper range.
2. The viscosity of the control ink must not be too high, especially for the double-squeegee flexo printing machine, which is usually used for high-viscosity inks. It takes 20-25 seconds for the DIN # cup. If you encounter this failure, you can first reduce the viscosity of the ink to an acceptable level for the product.
3. The speed of control can not be too high, the higher the speed, the greater the impact of ink on the blade.
4. Use a steel scraper with a knife tip. It is recommended to use a steel blade with a blade width of 1.3 mm, a blade thickness of 75 u and a blade thickness of 0.15 mm, with a hardness of 580 HV, so that the blade is tightly pressed against the anilox roller. When the anilox roller beats abnormally, the blade can also follow. With a slight beating, the blade cannot leave the anilox roller.
5. Under possible conditions, increase the pressure of the doctor blade on the anilox roller.
6. Adjust the ink pressure in and out of the ink tank so that there is no obvious ink viscosity in the ink tank. There should be no obvious ink retention area in the ink tank, or the high viscosity of this part may be caused. Scraper can not hide the hidden danger of ink impact.
The dark ink spots in the field version are rarely met on new flexo presses. Often the machine has been used for 3-4 years, and this problem has gradually emerged. The author came into contact with this problem after using a German flexo press for 3 years. In the field printing, we found small dark ink dots in the pattern, such as dark blue (blue+violet) version. In the even dark blue layout, there are many irregular ink dots with a diameter of 0.5mm or less. The color is deeper than the normal deep blue and observed with a magnifying glass. It is impossible to distinguish the boundary between dark ink dots and other uniform ink colors. At first, it was suspected that the temperature was too low to cause the ink resin to freeze. (The ink does contain some polyamide resin as well.) The paint was layered with the resin, and the ink was insulated before use and was stirred with a pneumatic mixer before use. Then suspect that the impurities in the ink, filtered with a multilayer filter, but also not effective. Later, it was discovered that when the speed of the vehicle slowed down, the dark-colored ink spots were significantly improved, and when the viscosity of the ink was high, the effect of the dark-colored ink dots was noticeable, and when the viscosity was low, the ink-dried ink dots showed a better improvement. In addition, the entire ink tank was The probability of dark ink spots near the ink tube is low, and the probability of dark ink spots near the ink return tube is high. The appearance of these phenomena prompted us to make a more comprehensive inspection of equipment and materials, and An analysis of the dark ink spots produced in the field version was obtained.
1. . Anilox roller beating. The anilox roller equipped with the new machine, the radial runout error is generally about 10-15 u, not too much, but after 3-4 years, due to wear, this parameter will appear error. After the anilox roller generates a radial runout, the blade cannot press it, causing jitter, resulting in dark ink dots of the same color.
2. When a flexo printer prints at a high speed, ink with a certain viscosity will form an impact force on the blade. The higher the speed, the greater the viscosity of the ink, and the greater the impact force. When the blade cannot withstand this impact, it will inevitably produce. Dark ink spots. In the fault phenomenon, the dark ink dots near the ink tube appear less and the dark ink dots near the ink return tube appear much more. It is precisely because of the ink pump that the ink flow at the ink tube is good and the viscosity is high. Low, and there are always some dead spots at the ink return tube, poor fluidity, and high ink viscosity.
3. Scraper configuration. The commonly used steel scraper with Swedish blue steel as the base material is about 0.15mm thick and has a hardness of 580HV. The commonly used cutter head is a round head, and the tip of a certain side is a certain slope and the tip is 1/2 blade thick. The function of scraper and scraper is to scrape the excess ink on the anilox roller. When the anilox roller beats, if the scraper is too soft, the excess ink on the anilox roller cannot be scraped. If the scraper is too hard, it can't cling. The anilox roller moves together. Therefore, even if the blade is pressed tightly against the anilox roller, the relationship between the anilox roller and the doctor blade, which has a certain error, is still fluent. It is precisely these dark ink dots in the field printing. If the ink is removed from the printing plate, a darker ink dot is formed than the normal ink color saturation.
Based on this, the dark ink dot solutions in field printing are:
1. Repair and solve the mechanical error, so that the anilox roller beating control within the proper range.
2. The viscosity of the control ink must not be too high, especially for the double-squeegee flexo printing machine, which is usually used for high-viscosity inks. It takes 20-25 seconds for the DIN # cup. If you encounter this failure, you can first reduce the viscosity of the ink to an acceptable level for the product.
3. The speed of control can not be too high, the higher the speed, the greater the impact of ink on the blade.
4. Use a steel scraper with a knife tip. It is recommended to use a steel blade with a blade width of 1.3 mm, a blade thickness of 75 u and a blade thickness of 0.15 mm, with a hardness of 580 HV, so that the blade is tightly pressed against the anilox roller. When the anilox roller beats abnormally, the blade can also follow. With a slight beating, the blade cannot leave the anilox roller.
5. Under possible conditions, increase the pressure of the doctor blade on the anilox roller.
6. Adjust the ink pressure in and out of the ink tank so that there is no obvious ink viscosity in the ink tank. There should be no obvious ink retention area in the ink tank, or the high viscosity of this part may be caused. Scraper can not hide the hidden danger of ink impact.
Author / Cai Chengji
Source: China Printing Materials Network
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