NMB miniature ball bearings are high precision devices compared to many mechanical parts. Good performance will therefore require treatment that takes into account their characteristics and operating environment.
A high percentage of bearing problems, including failures, are the result of improper handling procedures. The following information represents the results of our most common case studies. We hope you will find this information useful in the care and handling of precision ball bearings.
The performance of miniature precision ball bearings is critically affected by minute particle contamination. Particles as small as 0.005mm, once inside a bearing, can cause raceway scratches, abrasion and can decrease performance, shortened life, and generate acoustic noise and vibration. Avoiding exposing the bearing to any environment where particles may be present is highly recommended.
Shields and seals are used to prevent contaminants from reaching the inside of the bearing. However, after assembly, there is still a small gap between the shield and the inner ring. This gap may permit particle entry.
Please observe the following procedures carefully:
Since bearings are metallic products, they rust easily. Their treatment requires certain precautions:
Bearings are easily affected by shock forces. Depending on the size of the bearing, a shock force from a 100 gram weight at 4mm away could cause brinelling.
Brinelling could also occur when bearings are automatically press-fitted to a rotor shaft, if the shaft and bearing bore are not kept accurately in line.
A typical example of shock causing brinelling is when motors are placed on a conveyor belt. As the motors moved through the conveyor, the movement causes the motors to hit the iron plate underneath the conveyor, resulting in shock which causes brinelling to the bearing. Holes made to the iron plate prevent this type of shock force to be generated.
When bearings are mounted incorrectly, the balls will cause brinelling on the raceway and undermine bearing performance and life. Brinelling (dents and abrasions to the raceway) as small as 0.1 micron in depth will have an adverse effect on acoustic noise levels as well as causing increased torque levels.
Several general rules apply to mounting bearings.
When assembling a bearing with its shaft or housing, it is critical that no force be applied to the balls.
When mounting a bearing to a shaft, always press the inner ring.
When mounting a bearing into a housing, press the outer ring.
Never apply force to the outer ring when mounting a shaft, or to the inner ring when mounting into a housing. And never apply a shock load in either case.
When manually fitting a shaft into a bearing through its bore, do not force the shaft because it may cause brinelling to the bearing.
After gluing a bearing to a housing using a guide through the bearing bore, take the guide out very carefully or it may cause brinelling to the bearing.
When motors are being assembled, be aware that bearings may be attracted by the magnet and could slip from your fingers. To avoid this, hold the motor shaft in your palm, and cautiously insert the rotor.
For automated assembly, use an air cylinder, and steadily operate the assembly.
The environment in which bearings are used will largely determine their life. Chlorine gas, ozone and other chemicals will shorten bearing life, as the grease will become contaminated relatively quickly.
Generally, grease life will fail by half with every 10 ºC to 15 ºC that the ambient temperature increases. Therefore, it is critical to select the correct lubricant for the anticipated operating temperature.
About NMB Technologies Corporation - NMB Technologies Corporation, a Minebea Group Company, is the world's largest manufacturer of miniature precision ball bearings and a volume leader in the design and manufacturing of precision electro-mechanical components, including cooling fans, precision small motors and mechanical bearing assemblies, among others. NMB products can be found in the personal computing, networking, telecommunications, home entertainment, home electronics, automotive, medical and industrial markets.