How to Use Doctor Blades on Paper Machines Correctly

Doctor blade type:

Carbon fiber doctor blade: The perfect combination of carbon fiber and resin, suitable for cleaning equipment such as dryer cylinders, calenders, center rollers, and paper reel cylinders, and the self-lubricating property of carbon fiber, the high carbon content doctor blade has better self-lubricating property, is more wear-resistant, and can effectively protect the cylinder surface.

Glass fiber doctor blade: A general resin fiber doctor blade that can be used on many paper machines. It has a good cleaning effect in the press section and dryer cylinder. It is suitable for parts with high requirements for scraping and cleaning effects.

Polyethylene doctor blade: Cleaning doctor blade with a molecular weight higher than 1.2 million have significantly improved wear resistance and are suitable for rubber guide rollers in the wire section.

Metal doctor blade: mainly used for cleaning adhesives in paper machines with a speed below 500 meters. There are stainless steel, chrome steel, carbon steel, phosphor bronze, etc. in terms of material. The difference between chrome steel and carbon steel: compared with carbon steel, chrome steel adds some chromium, vanadium and other elements. The blade can guarantee good performance under high-speed friction and high temperature. The performance of chrome steel remains stable under high temperature.

Coating doctor blade: Use blue steel belt with good elasticity as the base material. The coating is required to have good toughness, strong bending resistance, and not easy to break during use; the coating at the tip of the blade has a dense structure.

Doctor blade use location:

Paper machine wire section

In order to achieve a good cleaning effect and protect the roller surface from damage to the maximum extent, the doctor blade of the paper machine wire department selects blades of different materials according to the different materials of each roller surface. For metal roller surfaces, carbon fiber doctor blade are generally used; ultra-high molecular weight polyethylene doctor blade, carbon fiber doctor blade and glass fiber doctor blade can be used for rubber rollers. The cleaning angle of 20-25° can be used to observe the doctor blade wear and angle changes; ultra-high molecular weight polyethylene doctor blade can be used for rubber rollers in the mesh (mesh guide rollers, tension rollers, correction rollers, and mesh drive rollers).

In addition, the two doctor blade of the vacuum roller should pay attention to the fact that the blade edges are one reverse and one positive. The first doctor blade fits tightly with the roller surface, so that the contact part between the roller surface and the blade edge forms a negative pressure, sucking out the fine fibers and impurities on the roller surface. The second doctor blade scrapes away the debris and fine fibers sucked out before while cleaning the roller surface.

Paper machine pressing section

It is recommended to use a polymer doctor blade for the rubber roller in the pressing section. If the pressing part is a stone roller, carbon 40, carbon 60, and full carbon doctor blade can be used. As the paper making filler increases, a large amount of sticky matter remains on the surface of the center roller. As it accumulates on the roller surface, it will cause the paper web to stick to the center roller and break, causing problems such as paper breakage.

In addition, the doctor blade of the net part must ensure that the blade lubrication water pressure is normal and fully covered, reduce the blade wear roller surface, and extend the service life. The angle of the net pressure part is generally less than 25 degrees. The line pressure is less than one kilogram.

Paper Machine dryer section

The dryer doctor blade is a device used to remove fine fibers, rubber and sticky substances brought in by waste paper pulp adhering to the surface of the dryer. Its main purpose is to keep the surface of the dryer clean and ensure the normal paper making process. At the same time, the doctor blade can also prevent the paper web from wrapping around the dryer when breaking and feeding paper.

It is recommended to use C40 doctor blade for the front group dryer and the front dryer tail cylinder, and glass fiber doctor blade can be used for other parts. Because the paper web of the front group dryer has high humidity and many aggregates and is hard, it is not easy to clean. It requires a material with high hardness, smoothness and non-adhesive aggregates.

The dryer of the paper machine is very critical. When selecting a doctor blade, you should consider the heat resistance, wear resistance, cleaning effect, and whether it can protect the surface of the dryer. It is recommended to use C40 doctor blade for the tail cylinder. When installing the scraper in the dryer section, adjust the angle to 25-28° and control the line pressure to about 200g/cm.

Calendering section

Calendering can be divided into soft calendering and hard calendering. It is recommended to use C60 and above carbon fiber doctor blade. Pay attention to the angle and pressure when using. The rubber roller used for soft calendering has a doctor blade angle of 15-17° and a line pressure of less than 200g/cm.

Winding section

It is also recommended to use C60 carbon fiber doctor blade for the winding section.