What is a doctor blade? What should we pay attention to in paper production?
What is Doctor Blade?
As a key part in paper making machine, the core function of doctor blade is to control the surface cleanliness of rollers through precise scraping and to protect and avoid or reduce the wear of equipment. According to different materials and application requirements, there are different types of paper making doctor blade. Common doctor blade include: carbon fiber doctor blade, glass fiber doctor blade, HDPE doctor blade, phosphor bronze doctor blade, stainless steel doctor blade, etc.
Application of Doctor Blade in Paper Machine
The doctor blade is mainly used to clean the roller surface, remove impurities (water, fine fibers and fillers) on the roller surface, and peel off paper sheets. As production progresses, the doctor blade will gradually wear out and cannot work effectively. The doctor blade needs to be replaced in time to maintain the cleaning function of the doctor blade system.
Characteristics of Doctor Blade
Carbon fiber doctor blade: The high hardness of the doctor blade can better resist friction and wear, reduce equipment downtime, and improve production efficiency. And the carbon fiber doctor blade can maintain a solid shape, improve the flatness and glossiness of the paper to ensure quality, and its excellent wear resistance and corrosion resistance reduce the loss of equipment during work and reduce production costs.
Glass fiber doctor blade: It has strong heat resistance and wear resistance, ensuring stable performance under high temperature environment, not easy to damage, and can remain unchanged under high pressure. It is suitable for use in high strength and high load environments.
HDPE doctor blade: This doctor blade is made of high density polyethylene and is also a common type of doctor blade in the paper making industry. It has strong chemical corrosion resistance and ensures stable performance when in contact with these chemicals. It also has good wear resistance and is not easy to wear after long-term use.
Phosphor bronze doctor blade: It has strong wear resistance and can maintain good cleaning effect for a long time under high pressure and high speed environments, and reduce downtime caused by wear. In addition, phosphor bronze contains phosphorus, which can form a protective oxide layer in the alloy, making phosphor bronze doctor blade have excellent performance in wet and chemical pulp environments.
Stainless steel doctor blade: It is suitable for use in high pressure and high load environments. It has strong strength and can withstand high pressure. It can still maintain stable performance even in high temperature environments.
Common Problems and Solutions of Doctor Blade
Common doctor blade wear
Uneven wear and tear, frequent replacement of doctor blade: This may be caused by poor roller surface, damaged clamping frame and vibration. Solution: If the roller surface is poor, use abrasive doctor blade or replace the clamping frame in time; if the clamping frame is damaged, repair it in time; eliminate vibration.
Local wear and tear of the doctor blade: This may be caused by static electricity or damage to the clamping frame. In this case, the clamping frame needs to be repaired or replaced; if it is caused by static electricity, a synthetic doctor blade needs to be used.
Excessive wear on one end of the doctor blade: This is caused by poor adjustment of the doctor blade and the uneven level with the roller. The doctor blade needs to be readjusted to correct the level.
Excessive wear of the doctor blade corresponding to the width of the pulp part: This phenomenon is typical wear of the press roller doctor blade, which is caused by excessive lubrication of the roller surface in the pulpless part.
How to Use Doctor Blade Better and When to Replace The Doctor Blade
The replacement of the doctor blade depends on many factors (application location, paper break, temperature, roller surface material and doctor blade material, etc.). Some special equipment or special parts require more frequent replacement and maintenance of the doctor blade. Below, Sun Hong tells some general and effective experience, which can make full use of the doctor blade to optimize the performance and extend the service life of the doctor blade.
(1) Select the appropriate doctor blade material according to the application location of the paper machine.
(2) Regularly maintain and check the doctor blade and doctor blade system.
(3) Replace the doctor blade at any time when the paper machine is shut down for cleaning.
(4) Observe the doctor blade, customize the replacement cycle for the doctor blade at key positions, and replace it regularly.
When using the doctor blade, properly maintain the doctor blade fixture, doctor blade system or roller surface cleaner to ensure that the loading and alignment of the entire roller surface are consistent, which can quickly improve and optimize the performance of the doctor blade.
Measure and analyze the wear condition of the doctor blade after use. This is an effective way to analyze and determine whether the doctor blade system is normal.
