In the technical transformation of the air knife into a scraper, the coating scraper feeding system should be modified; the shape of the scraper is determined, the back roller model is selected reasonably; the paint circulation system is modified; and the electrical technical parameters are reasonably set. Therefore, the doctor blade coating machine scrapes off the excess paint after applying the paint to the paper surface, and smoothes the surface of the coating.
The advantage of the doctor blade coating machine is that the coated surface is very flat and is not affected by the surface condition of the base paper; the coating is not required to be soft and fluid, and high solids coating and high speed coating are possible. The disadvantage is that when the foreign matter is mixed into the paint, it is easy to get stuck in the knife edge, leaving long streaks on the paper surface, and the scraper blade is easy to wear, and must be replaced frequently; the coating is generally not too thick, and the thickness uniformity of the base paper is required. It is also stricter.