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Selection and Judgment of Vibration Levels Z1/Z2/Z3 for Deep Groove Ball Bearings

 Vibration level not only determines the noise performance of the bearing during operation, but also indirectly reflects the raceway machining accuracy, assembly quality, and internal defect control level.

How to Measure Vibration: Two Physical Quantities with Different Emphases

 

The quantification of bearing vibration mainly relies on two physical quantities:

* Vibration Acceleration Level (dB): Sensitive to high-frequency impact signals, capable of detecting early defects such as minute spalling and pitting on the raceway surface, suitable for quality grading of precision bearings.

* Vibration Velocity (μm/s): Closer to the low-frequency vibration range perceptible to the human ear, suitable for evaluating the overall operational smoothness and noise level of the bearing.

 

These two are not substitutes, but complements each other. The acceleration method focuses on "discovering hidden problems," while the velocity method focuses on "evaluating the experience."

 

What do Z1, Z2, and Z3 represent?

 

According to the JB/T 7047-2006 standard, the vibration limits for deep groove ball bearings are divided into three levels: Z1, Z2, and Z3. The higher the level, the stricter the vibration limit, and the quieter and smoother the bearing operation.

 

Z1: General industrial transmission, ordinary motors, cost-priority, optional when no quiet operation is required.

 

Z2: Mainstream choice for conventional working conditions, recommended for most equipment.

 

Z3: Precision machine tool spindles, high-end motors, medical equipment, selected when strict requirements for noise and vibration are in place.

 

For most conventional working conditions, level Z2 is sufficient and offers the best cost-performance ratio.

 

Comparison of Vibration Limits for Different Inner Diameter and Diameter Series

 

Taking deep groove ball bearings with nominal inner diameters of 20~120mm and 0-group clearance as an example, the limits for different diameter series differ under different vibration levels. The larger the inner diameter and the wider the diameter series, the more relaxed the permissible vibration limits. Purchasing and quality control personnel can quickly determine whether a bearing meets standards by matching the specific model number.

 

Measurement Methods and Key Process Requirements

 

Bearing vibration measurement follows two industry standards: JB/T 5314: Acceleration Method, applicable to high-frequency defect detection; JB/T 5313: Velocity Method, applicable to overall vibration assessment.