Doctor Blade Installation and Application
Doctor blade installation
(1) Clean the doctor blade holder and roller surface: Make sure the installation surface is clean and free of impurities.
(2) Check the doctor blade: Check whether the doctor blade edge is sharp, damaged, and the size is correct.
(3) Install the doctor blade: Put the doctor blade into the doctor blade holder, pay attention to the installation direction of the doctor blade, and ensure that the blade contacts the roller surface in the correct direction.
(4) Fix the doctor blade: Tighten the fixing bolts or clamping device of the doctor blade holder, but do not tighten too much to avoid damaging the doctor blade or doctor blade holder.
(5) Adjust the doctor blade angle and pressure: Adjust the doctor blade angle and pressure according to the process requirements and doctor blade type.
(6) Check the doctor blade operation status: Start the machine and observe the contact between the doctor blade and the roller surface, the scraping effect, and whether there is abnormal vibration or noise.
Adjust the doctor blade installation angle
The doctor blade installation adopts a sharp angle and a small angle, which has a good scraping effect, but it will cause the doctor blade and roller surface to wear more, it is easy to produce knife lines, and the pressure is concentrated. This angle is suitable for cleaning doctor blade and quantitative doctor blade.
If a large angle and an obtuse angle are used, the scraping effect is relatively poor, but the doctor blade and roller surface are less worn, the pressure is dispersed, and it is not easy to produce knife lines. Suitable for stable doctor blade and guide doctor blade.
About doctor blade pressure adjustment
When the pressure is too small, it will lead to unclean scraping, residual impurities on the roller surface, and easy doctor blade jumping. Excessive pressure will damage both the roller surface and the doctor blade, increase energy consumption, and easily produce knife lines.
The correct approach should be to make the doctor blade fully contact with the roller surface, scrape clean impurities, and avoid excessive wear and knife lines. The pressure adjustment needs to be gradual, gradually increase the pressure, observe the scraping effect and doctor blade state, and find the best balance point. doctor blade and roller surfaces of different materials have different optimal pressure ranges.
Doctor blade running-in
In order to make the doctor blade and the roller surface fully contact, eliminate tiny burrs and unevenness on the blade, improve the scraping effect, and extend the service life.
After the new doctor blade is installed, it can be run at a low pressure for 2 hours. During the running-in process, the doctor blade pressure is gradually increased. After each pressure increase, it is run for a period of time to observe the scraping effect and doctor blade status. After the running-in is completed, check the contact between the doctor blade and the roller surface to ensure uniform contact and no gaps (in addition, the running-in time needs to be determined according to factors such as the doctor blade material, roller surface material, and vehicle speed, usually a few hours to a few days).
Maintenance and replacement of doctor blade
(1) Daily maintenance of doctor blade requires regular inspection of doctor blade wear. You can observe the sharpness of the doctor blade, the thickness of the blade body, and whether there are cracks or gaps.
(2) Ensure that the doctor blade is firm and not loose.
(3) Clean the doctor blade holder regularly to remove accumulated impurities.
(4) Keep the moving parts of the doctor blade holder lubricated to ensure flexible movement.
The need for replacement depends on factors such as the doctor blade material, roller surface material, vehicle speed, and load. Metal doctor blade have a shorter lifespan, while plastic and ceramic doctor blade have a longer lifespan. A reasonable replacement cycle should be established based on the actual situation and the degree of doctor blade wear. If the doctor blade is severely worn, the scraping effect is significantly reduced, and knife lines and damage to the roller surface appear, the doctor blade should be replaced immediately.
Doctor blade material: The doctor blade material is the key to selection and directly determines the performance, lifespan and cost of the doctor blade. The following factors need to be considered comprehensively:
Roller surface material: metal roller (cast iron, steel, alloy steel, stainless steel), rubber roller (natural rubber, polyurethane rubber roller), ceramic roller, carbon fiber roller, etc. The hardness of the scraper material should be slightly lower than or equal to the hardness of the roller surface material to avoid damage to the roller surface due to excessive scraper hardness.
Doctor blade classification and application scenarios
Carbon fiber doctor blade is the most widely used doctor blade on the market. It has good self-lubrication and temperature resistance up to 200 degrees. It can effectively solve the problem of rough roller surfaces that are difficult to clean. It is suitable for hard rubber rollers in the drying section, pressing section and mesh section.
Glass fiber doctor blade is made of high-temperature enhanced resin adhesive and special lubricating and wear-resistant materials. It enhances the cleaning performance and is wear-resistant and high-temperature resistant, making it very suitable for areas with high cleaning requirements.
HDPE doctor blade has excellent performance on various hard rubber rollers, soft rubber rollers, rubber rollers and polyurethane rollers.
Phosphor bronze doctor blade has a soft texture and is commonly used in Yankee dryer cylinders and cast iron rollers. It can effectively remove impurities on the surface without damaging the rollers.
Stainless steel doctor blade is suitable for pressing stone rollers and hard rubber rollers in the pressing section.
SK-5 doctor blade is also a widely used metal doctor blade with excellent strength, toughness and wear resistance. It is commonly used in low-speed drying cylinders, Yankee wrinkling scrapers and cleaning doctor blade..
Attention should be paid to the use of doctor blade
(1) Correctly select the doctor blade type and material: Wrong doctor blade selection may lead to poor scraping effect, short life, roller surface wear, increased paper defects, low production efficiency and other problems.
Solution: Before purchasing, it is recommended to ask the manufacturer to understand the characteristics of different types of doctor blade and materials. Sun Hong can scientifically select and provide you with an integrated solution based on your needs and actual working conditions.
(2) During installation, strictly follow the installation instructions of the doctor blade and doctor blade holder to ensure that it is installed in place, fixed firmly, and the angle and pressure are adjusted accurately.
(3) Avoid collision between the doctor blade and hard objects: Collision is likely to cause damage to the scraper blade, deformation of the blade body, and damage to the doctor blade holder, affecting the performance and life of the doctor blade. When transporting, installing, replacing, and maintaining the doctor blade, the movement amplitude should not be too large to avoid collision.
There are skills in each operation of doctor blade, from selection, installation, adjustment, maintenance to replacement. Only by constantly learning advanced experience according to one's own actual situation and continuously optimizing doctor blade management can the doctor blade be fully utilized, the paper quality can be improved and the production cost can be reduced.
