Linear bearing block loose?

[andrew]

I was hearing some pretty loud/noticeable vibration type buzzing the last couple times I've ran my machine.  It started faintly but seemed to increase each time.  It only really makes the noise on certain movements of the machine, so it's not constant but maybe 25% of the time things are running.  I decommissioned my machine for a bit to install the laser, wait for and install the electronics upgrade, and try and isolate where the buzzing is coming from. I thought maybe the router mount was loose or something but it wasn't.

I think I've narrowed it down to one (maybe more) of the linear bearing blocks.  Not the block itself being loose on the Z axis plate, but the bearing hole where the steel rod goes through.  I can wiggle the z axis plate and see/hear a slight but noticeable movement of the rod in the hole..  particularly the upper left block.

I guess my questions are:  Is this normal?  Do those loosen up over time?  Anyone else ever have this issue?  How can I fix it?
Thanks for any insight or suggestions...

You can hear the buzzing in the beginning and intermittently throughout the attached video..

[Derek the Admin]

Could possibly be that the rod is a little on the low side of tolerance and the bearing is a little on the high side. My first suggestion would be to see if we can get some preload against that rod by taking that upper left row support and adjusting it a little left or right. If that doesn't get ya where you need I can send ya another bearing. I think the adjusting the rod support will get it, but if not let me know.

[andrew]

Thanks for the suggestion, that makes sense. I'll try that this afternoon and see if it tightens up!