3. Missing dots
During the printing process, the even flat screen on the printing plate can not be leveled because of the ink, and the dots appear alone, forming a filter-like network, and even missing dots. Generally starting from the second color group, this phenomenon is more obvious.
cause:
1 ink viscosity or yield value is too high, resulting in poor ink transfer.
2 The ink dries too fast, is not evenly distributed on the plate, and is prematurely dried and solidified.
3 Poor wettability between the ink and the plate (surface tension does not match), the transferred ink is not easy to spread.
4 The pressure of the blade is high, but the pressure of the printing roller is insufficient.
5 printing plate cable is too thick, the gap between the large network, the ink is not easy to spread.
solution:
1 To reduce the viscosity of the ink and improve the transferability of the ink, it is recommended to use the special 20# additive for gravure ink.
2 Adjust the position of the squeegee holder so that the distance between the squeegee and the plate cylinder is shortened.
3 Use a slow-drying solvent to reduce the ink drying rate and increase the dot gain.
4 Adjust the blade pressure and the print roller pressure.
5 Re-plate to change the shape and angle of the cell.
6 Change to a low viscosity ink.