THK Linear Motion Bearing
Contact fatigue failure refers to the failure of the THK linear motion bearing working surface subjected to alternating stress.
What are the reasons for the failure of THK linear motion bearing?
1.Contact fatigue failure
Contact fatigue failure refers to the failure of the THK linear motion bearing working
surface subjected to alternating stress. Contact fatigue spalling occurs on the working surface
of THK linear motion bearing, often accompanied by fatigue cracks, first from the maximum
alternating shear stress below the contact surface, and then extended to the surface to form
different exfoliation shapes, such as pitting or pitting Peel off and peel off into small pieces
called shallow peeling. Due to the gradual enlargement of the exfoliation surface, it tends to
expand deeper and form deep exfoliation. Deep exfoliation is a source of fatigue in contact
2. Wear failure
Wear failure refers to the failure of the relative sliding friction between the surfaces
resulting in the continuous wear of the metal on the working surface. Continued wear and
tear will cause gradual damage to the bearing components and ultimately lead to loss of
bearing dimensional accuracy and other related problems. Wear may affect the shape change.
The increase of the clearance and the change of the surface of the working surface may affect
the lubricant or cause the pollution to a certain extent, resulting in complete loss of the
lubrication function, thus causing the bearing to lose the rotation precision or even the
normal operation. Wear failure is one of the common failure modes of various types of
bearings. It is usually classified into the most common abrasive wear and adhesive wear
according to the form of wear.
3. Fracture failure
The main reason for the failure of THK linear motion bearing is the two factors of defect
and overload. When the applied load exceeds the material strength limit and the part is
broken, it is called overload fracture. The main reason for the overload is the sudden failure of
the host or improper installation. The defects such as microcracks, shrinkage cavities, air
bubbles, large foreign objects, overheated tissue and localized burns of THK linear motion
bearing parts also cause breakage at the defects during impact overload or severe vibration, which is called defect fracture. It should be pointed out that in the manufacturing process, THK
linear motion bearing can correctly analyze whether the above defects exist through the
instrument in the process of re-inspection of raw materials, quality control of forging and heat
treatment, and process control, and it is necessary to strengthen control in the future.
However, in general, most of the THK linear motion bearing failures that occur are overload
4. The gap change fails
In the work of THK linear motion bearing, due to the influence of external or internal
factors, the original matching gap is changed, the precision is reduced, and even the “biting
death” is called the gap change failure. External factors such as excessive interference,
inadequate installation, expansion caused by temperature rise, instantaneous overload, etc.,
internal factors such as residual austenite and residual stress are unstable, which are the main
reasons for the failure of the gap change.
1).THK linear motion bearing If it is well lubricated and properly blocks debris and
moisture, it means that the oil seal should be free of wear. However, it is best to check the
bearing and periodically check the oil seal when opening the bearing housing. Check the
bearing close to the bearing. The condition of the oil seals is to ensure that they are sufficient
to prevent hot liquid or corrosive liquids or gases from penetrating into the bearing along the
axis. If the oil seal is worn, it should be replaced as soon as possible.
2). High temperature often indicates that the THK linear motion bearing is in an abnormal
condition. High temperature is also harmful to the lubricant in the bearing. Sometimes the
bearing overheating can be attributed to the lubricant of the bearing. If the bearing runs for a
long time at a temperature exceeding 125 degrees Celsius, it will decrease. Bearing life.
Causes of high temperature bearings include: insufficient lubrication or excessive lubrication,
magazines in the lubricant, excessive load, bearing damage, insufficient clearance, and high
temperature friction caused by the oil seal.
3). Check the condition of the running machine and monitor it to avoid equipment
5. Reasons for the structure
The cage is the weakest part of the THK linear motion bearing, which means that the cage
is the most tolerant of the bearing components (the roller hits the cage when entering and
leaving the load zone), so the cage Insufficient strength is often the cause of bearing damage.
1) The material itself has impurities
2) insufficient sealing, impurities entering
7. Excessive force
8. Improper installation (eccentricity, etc.)
9. Poor lubrication
10. Improper clearance setting
Generally speaking, these reasons are mixed. For example, if the axial force is too large,
the local lubrication is seriously insufficient, and the oil film cannot be formed. When the
clearance is too large, the bearing area is too small, the force is “relatively” too large, and
the clearance is too large. Small oil film is difficult to form and so on. There are also internal
defects, such as unqualified tissue, cracks, inclusions, etc., may also be external causes, fatigue
failure, burning caused by poor lubrication, mechanical damage caused by foreign bodies.