Air knife coating stands out as the preferred and highly efficient coating method among various coating machine manufacturers in China. Its distinct advantage lies in avoiding direct contact with the paper surface and instead removing excess paint through air pressure. This makes air knife coating especially suitable for in-machine coating and cardboard applications. Saving paint in this process is crucial for maintaining the specified coating amount while ensuring quality, preventing paint waste, and reducing overall costs.

Coating Solid Content:

Air knife coating exhibits unique characteristics, such as a relatively high coating weight (10-40g/m2) and a low required solid content (20-50%). Beyond 60% solid content, issues arise, including increased coating amount, uneven coating, cylinder adhesion, powder fallout, spray back, air knife clogging, foam buildup, overflow blockage, and material trough obstruction. Moreover, higher vehicle speed and temperature can contribute to excess paint and hinder efficient operation. To counteract this, it is advisable to decrease the solid content of the paint with increasing vehicle speed and temperature. This not only conserves material but also reduces the drying load.

Coating Chemical Supply:

Leakage from the material pump not only results in wastage but also poses environmental concerns. The presence of stone powder in the paint can accelerate wear and leakage in the material pump. Using an anti-wear and anti-seepage material pump is recommended. Since the solid content in air knife coating is not high, a general non-clogging sewage pump is suitable, helping save energy, maintenance costs, and preventing leakage. Proper placement of the material trough, away from heat sources, is essential to prevent paint solidification due to heat.

Quality of Base Paper:

Strict adherence to an appropriate drying curve for the base paper entering the drying section is crucial. Maintaining paper dryness at around 90% upon exiting the dryer ensures good calendering effects, moderate water absorption, and optimal coating adherence. Adjusting base paper dryness prevents issues such as thick "filter cake," uneven coating, and insufficient whiteness. Minimizing base paper defects, such as holes, broken edges, and paper breaks, is also essential.

Air Knife Operation:

Optimizing the air knife operation involves careful adjustment of the knife angle, pitch, gap, and wind pressure. The knife angle, typically ranging from 0-15°, affects the depth of the blow shovel and, consequently, the amount of blown-off paint. Balancing the knife pitch, distance between the knife edge and lining roller surface (2-8mm), ensures effective air knife airflow without scratching the base paper. Maintaining an appropriate knife gap (0.5-1.5mm) is essential to prevent blockages. Additionally, controlling wind pressure within the range of 10-60Kpa helps maintain an optimal coating amount. Proper adjustments to the belt roller speed, pressure of the paper roller, and tension in the base paper contribute to uniform coating. Attention should be paid to avoiding excessively tight or loose conditions, as they can impact coating quality. Lastly, limiting the coating width helps reduce waste paper, optimizing material usage.