1.      Background

Bearing Type7017AD/7015C

Bearing ArrangementDBT/DB (<>> / <>)

Rotating Speed5000 RPM

PhenomenonNoise 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.


NoteFTF: 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

3.          Conclusion

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.


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