I have a centrifugal basket machine spindle bearing that was rebuilt in March 2019. Upon doing a quality check after the rebuild, it was noticed that there was a high 4x peak on the spindle. The machine was inspected and it was noted that there was nothing out of the ordinary. Short of pulling the spindle again, there was nothing more to do besides monitor the condition of it.
Several months later (now), the spectrum has become distorted around this and other surrounding frequencies. I am writing a work order for this spindle to be rebuilt based on the change in the spectrum, but I am trying to figure out what is actually going on here.
My initial thought was resonance, but I was unsure why this would occur after the spindle bearing rebuild. We have several other machines like this and I have never seen this before.
My current thought is some sort of rubbing or clearance issue in the bearing that has become a looseness problem based on the raised noise floor around the initial high amplitude frequency.
I appreciate your thoughts and time!