Can motor abnormal noise and general noise be improved by bearing materials?

Points to Check When Selecting Materials for Oil-Impregnated Bearings

Do you experience abnormal noises such as "squeaking" or "hissing" from motors, or increased noise during long hours of operation? Various factors are related to abnormal motor noise, including assembly precision, shaft surface condition, and lubrication conditions. Therefore, if abnormal noise occurs, it is necessary to check the causes one by one. One of the easily overlooked points among these is the **combination of bearing material and shaft**.

Main Causes of Abnormal Noise from Motors

The main causes of abnormal motor noise are considered to be the following:

• Insufficient conformity between bearing and shaft
• Insufficient or deteriorated lubricating oil
• Improper clearance between bearing inner diameter and shaft diameter
• Wear of bearing or shaft
• Shaft surface roughness or scratches
• Bearing deformation due to press-fitting
• Insufficient motor assembly precision
• Combination of bearing material and shaft material
• Lubricating oil viscosity or characteristics not matching operating conditions

To improve abnormal noise, it is important to check not only the bearing but also the shaft, housing, lubricating oil, and assembly conditions.

Reasons Why Sound Changes Depending on Bearing Material

Oil-impregnated bearings are components that support rotation while directly contacting the shaft. Therefore, the hardness and conformity of the bearing material affect vibration and sound during sliding. General iron-based oil-impregnated bearing materials excel in mechanical strength and load capacity. On the other hand, depending on operating conditions and the combination with the shaft, initial break-in may take time. Copper-based oil-impregnated bearing materials are generally softer than iron-based materials and have the characteristic of conforming easily to the shaft surface. This can alleviate localized contact and minute vibrations, potentially leading to a reduction in sliding noise. However, using copper-based materials does not solve all abnormal noise issues. It is necessary to comprehensively evaluate factors such as load, rotational speed, operating temperature, and shaft surface roughness.

Material Selection Points When Prioritizing Quietness

1. Conformity to the shaft

The more easily the bearing material conforms to the shaft surface, the easier it is to suppress localized contact and vibration. Especially in small motors, even slight vibrations can be transmitted as sound to the outside of the product, making initial conformity an important evaluation item.

2. Characteristics of impregnated oil

In oil-impregnated bearings, oil impregnated into the pores within the sintered material is supplied to the sliding surface. If the oil's viscosity or temperature characteristics do not match the operating conditions, a sufficient oil film may not form, potentially increasing friction and abnormal noise.

3. Bearing and shaft clearance

If the clearance is too small, friction and heat generation increase; if too large, vibration and rattling are more likely to occur. When press-fitting a bearing into a housing, the inner diameter may contract, so design must consider dimensions after press-fitting.

4. Shaft surface roughness

If the shaft surface is too rough, it may damage the bearing surface or hinder oil film formation. It is necessary to check not only the material but also the shaft's hardness, surface treatment, and surface roughness.

5. Load and rotational speed

If soft materials are selected solely based on quietness, wear and deformation may occur depending on load conditions. In actual selection, the balance between quietness and load capacity is important.Applications Suitable for Copper-Based Oil-Impregnated BearingsCopper-based oil-impregnated bearing materials are a strong option under the following conditions:

• Want to suppress motor operating noise
• Want to enhance product quietness
• Want to prioritize initial conformity with the shaft
• Want to suppress rust generation
• Want to use in small, light-load motors
• Want to maintain stable rotation over a long period

On the other hand, for high-load applications or applications prioritizing material cost, iron-based or iron-copper-based materials may be more suitable.

"No.1-H" Suitable for Quiet Applications

Peace-Lon's "No.1-H" is a general-purpose copper-based oil-impregnated bearing material equivalent to JIS P4013Z. With copper and tin as main components, it excels in conformity to the shaft and quietness, making it suitable for applications where operating noise affects product quality, such as small motors, audio equipment, OA equipment, and FAN motors. However, when considering material replacement, it is necessary to check not only the material of the currently used bearing but also factors such as load, rotational speed, dimensions, shaft material, and lubrication conditions.

Do Not Judge Abnormal Noise Countermeasures Based on Material Alone

While abnormal motor noise can sometimes be improved by changing the bearing material, if the cause of the noise lies in assembly precision or shaft shape, changing the material alone may not yield sufficient results. Therefore, it is important to consider the following sequence:

1. Check the conditions under which abnormal noise occurs.
2. Check the dimensions of the bearing, shaft, and housing.
3. Check the wear and contact conditions.
4. Check the type and oil content of the lubricating oil.
5. Evaluate the effect of changing bearing material through prototyping.

Material Selection Support by Peace-Lon Vietnam

Peace-Lon Vietnam supports material selection for sintered oil-impregnated bearings and sintered mechanical parts according to application and operating conditions. We organize requirements such as quietness, wear resistance, load capacity, corrosion resistance, and cost, and provide consistent support from material selection to prototyping, evaluation, and mass production. If you are experiencing issues with abnormal motor noise, by providing your current bearing material and operating conditions, we can propose more appropriate improvement methods.