Do You Know About The Coating Blade?
Coating Quality Issues Caused by The Coating Blade
In the paper coating process, improper selection, adjustment, or wear of the coating blade may lead to various coating quality defects. Common issues related to paper machine coating blade include the following:
Common Problems With Creping Blade During Paper Machine Operation
Uneven coating: Uneven coating thickness occurs when the coating liquid is not uniformly distributed on the paper surface. This is often caused by uneven blade pressure, poor coating fluidity, improper blade angle, or excessive wear of the coating blade.
Scratches: Due to foreign matter on the doctor blade edge, impurities in the coating material, wear of the doctor blade, or mismatched hardness of the coating blade, fine scratches may appear on the coated surface, thus damaging the integrity of the coating.
Missed coating: Local uncoated areas may occur as a result of improper blade setting, insufficient coating supply, or poor contact between the paper machine coating blade and the backing roll, leading to blank or thin coating zones.
Blade marks: Blade marks on the coating surface are usually caused by factors such as excessive doctor blade hardness or poor contact between the doctor blade and the panel, affecting the smoothness and surface uniformity of the coating.
Coating defects and anomalies: Improper coating formulation or mismatch between the coating blade and the coating medium may lead to problems such as coating cracking, discoloration, and oxidation during the blade coating process.
Maintenance and Care of Coating Blade
Regular inspection: Regularly inspect the coating blade, including checking the wear condition of the blade edge, the gap between the doctor blade and the coating roller, and the tightness of the doctor blade's fixing screws. If any abnormalities or severe wear are found, it is necessary to replace or repair it in a timely manner.
Regular cleaning and maintenance of the coating blade is necessary to remove residues and impurities from its surface, ensuring it remains clean and smooth. Additionally, care should be taken to avoid scratching the blade surface with hard objects or sharp tools, as this may damage the doctor blade.
Replace worn parts: If any parts of the coating blade (such as the blade edge, support frame, etc.) are found to be severely worn or damaged, they should be replaced promptly to ensure the normal operation of the blade and the quality of the coating.
Lubricating the squeegee: For squeegees that require lubrication, apply an appropriate amount of lubricant regularly to reduce friction between the squeegee and the coating roller and minimize wear.
Comprehensive inspection: Regularly conduct a comprehensive inspection of the coating blade, including the electrical system, transmission system, lubrication system, etc., to ensure that all components operate normally without abnormal noise or vibration.
Application of Doctor Blade Coating
Material: The blade coating technique is suitable for substrates of various materials, including paper, plastic, metal, glass, etc. However, high requirements for the surface flatness and dimensional stability of the substrate are necessary in blade coating to avoid defects such as uneven coating thickness, deformation or shrinkage, bubble formation, and scratches.
Coating liquid solid content: 50% to 60%; viscosity: 1000 to 300000 MPa·s; coating amount: 6 to 30 g/m2.
The coating liquid should remain stable during the blade coating process and should not undergo chemical reactions with the coating blade or the substrate.
Applications of Coating Blades in Other Industries
Packaging industry: Used for coating adhesives, inks, etc., to achieve functions such as bonding and printing of packaging materials.
Electronics industry: Used for coating conductive ink, insulating coatings, and other materials to enhance the performance and reliability of electronic components.
Construction industry: used for coating waterproof materials, insulation materials, etc., to enhance the waterproof performance and insulation effect of buildings.
Automotive industry: Used for coating anti-corrosion coatings, sealants, and other materials to protect automotive components from corrosion and wear.
Optics industry: used for coating various optical thin film materials to achieve specific optical effects.
