How to determine the dosage of powder coating is a difficult problem because there is no specific data. The amount of powder should not be too small or too much, which can only be determined by the operator's continuous exploration and experience accumulation. So how to determine the amount of powder in the flexographic printing machine?
1. Product ink layer thickness
The thicker the ink layer, the dirtier the product and the greater the amount of powder sprayed, and vice versa.
2. Chimney height
The height of the stack is getting higher and higher, and the gap time between the sheets is getting smaller and smaller. The greater the molecular bonding force between the ink film surface on the print and the next print, the more likely it will cause the back of the print to be smudged, so the amount of powder spray should be increased.
3. The nature of the paper
Generally speaking, the rougher the paper surface is, the better it is to improve the permeability of the ink and the drying of the oxidized conjunctiva. The amount of powder spray can be reduced or eliminated.
However, for rough art paper, opposite electrostatic paper and acid paper, the surface of the paper is not smooth enough, which is not conducive to the drying of ink, and the amount of powder should be appropriately increased.
4. Properties of the ink
For different types of ink, the composition, proportion and drying speed of binder and pigment are different, and the amount of powder spraying is also different.
In the printing process of the flexographic printing machine, usually due to the needs of the product, some ink blending oil or degumming agent will be added to the ink to adjust the printing adaptability of the ink in the near future to reduce the viscosity of the ink, thereby reducing the ink. Its own cohesion prolongs the drying time of the ink and increases the risk of friction on the back of the product. Therefore, the amount of powder spraying should also be appropriately increased.
5. PH value of fountain solution
The smaller the pH value of the fountain solution, the more serious the emulsification of the ink, and the easier the ink cannot be dried in time. The amount of powder should be appropriately increased.
6. Printing speed
The faster the flexo press, the shorter the embossing time, the shorter the ink penetration into the paper, and the less powder sprayed on the paper. In this case, the dosage of powder spraying should be appropriately increased.
