Classification Of Coating Machines
Brush Coating
Brush coating machines represent the oldest type of coating equipment; they were first utilized in the 1850s for the production of coated wallpaper using china clay-based coatings. Brush coating heads are classified into three distinct types: round brush heads, blanket roll heads, and blanket sleeve heads. Figure 1 illustrates an early-model brush coating head.
Air Knife Coating
The advent of the air knife coater in the 1930s marked the birth of the modern paper coating industry. By effectively overcoming the aforementioned drawbacks of brush coating machines, the air knife coater was rapidly adopted, leading to a dramatic surge in the production volume of coated paper.
Blade Coating
The first patent for a blade coating machine was issued in the 1950s. Since then, blade coating technology has undergone rapid development. Depending on the coating application mechanism, blade configuration, and blade mounting position, blade coating heads are categorized into numerous varieties, such as rigid blade coaters, trailing blade coaters, flexible blade coaters, fountain-feed blade coaters, short-dwell blade coaters, Bill blade coaters, and roll-blade coaters.
Roll Coating
Roll coating involves applying a coating medium to a surface using a coating roll; this method predominates in "on-machine" coating applications. The coating weight can be regulated by adjusting the pressure between the metering rolls: increasing the pressure reduces the volume of coating passing through, thereby decreasing the coating weight applied. Types of roll coating machines include:
1. Squeeze roll coating heads
2. Reverse roll coating heads
3. Transfer roll coating heads
4. Gravure roll coating heads
Spray Coating
Spray coating is a non-contact coating technique that utilizes controlled high-pressure spray technology to apply coatings (or sizing) to one or both sides of paper or cardboard substrates. Curtain Coating
A multi-layer curtain coater is capable of imparting a three-layer structure (comprising a base layer, an absorption layer, and a top layer) to the surface of inkjet printing paper in a single coating operation, while simultaneously achieving a uniform coating even on uneven paper surfaces.
Slot Coating
A slot coating head comprises a coating fluid reservoir; a pump, utilized to pressurize and convey the coating fluid from the reservoir to the nozzle via a supply line; a control unit, responsible for regulating the operation of the pump and the nozzle; and a pressure detection unit, designed to monitor the pressure within the line, ensuring that the nozzle dispenses the coating fluid only when the pressure reaches a predetermined threshold.
