Precision Bearings Application Case Study (2)
Bearing Arrangement：DBT/DB (<>> / <>)
Rotating Speed：5000 RPM
Phenomenon：Noise was found at 4000RPM during running-in test.
2. Investigation and Research
From FFT diagram at 4000RPM, vibration was mainly come from 2 times, 3 times and 4 times frequencies, which lead to the noise occurrence. As shown in Fig. 1 and 2.
Note：FTF: Fundamental Train Frequency, BSF: Ball Spin Frequency, BPFO: Ball Pass Frequency Outer, BPFI: Ball Pass Frequency Inner.
Fig. 1 7017AD side FFT diagram
Fig. 2 7015C side FFT diagram
Amplitude at 2 times, 3 times and 4 times frequencies was obviously lowered and so did the noise level. As shown in Fig. 3 and 4.
Fig. 3 7017AD side FFT diagram
Fig. 4 7015C side FFT diagram
From FFT diagram, the vibration and noise were caused by 2 times, 3 times and 4 times frequencies, which might be related to bearing looseness. After investigation, bearing inner ring and the spindle shaft has no interference was found out. Hence, a new spindle was selected for appropriate interference and the vibration and noise were obviously reduced.