Bearing rattle sound?

Hi folks,
I’m noticing a vibration on my Y (long) axis. I replaced the bearings thinking that would solve it but its still there. I’ve checks everything around for tightness of fasteners. I don’t know for sure but I think the sound is coming from the bearings? Or maybe its the R/P?

I have a link below to a short video. I think you should be able to hear what I’m talking about. Its a lower frequency “rattle” sound you can hear over top of the motor hum. Anyone else come across this?

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Sounds like the belt is climbing off the gears to me. I haven’t quite figured out the belt tensioning part of these myself and have issues like this sometimes because of it. Might be your problem, might not?

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You can test the bearing blocks by backing off the drive pinion and moving the axis by hand. It should not make any noise that way.

I can think of three things that might make that noise:

  1. Belt tension. If the belt is too loose or too tight, it could vibrate at resonance. You should be able to deflect the belt a little by pressing on it, but not much, maybe 1-3mm.

  2. pinion tension. Back off the pinion tensioning bolt and re-tension. Make sure you stop when it first takes out the slack, then turn in three more turns, and make sure the bolt and spring aren’t catching on anything.

  3. Stepper microstepping set to low. At 200 steps/rotation you’d hear a hum from the steppers; at 1600 s/r not so much, etc. I would be very surprised if this were the cause, but I’m including it for completeness.

Bonus 4. If the R&P are worn enough, the pinion teeth would be hitting at their tips instead of their faces.

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Sounds like it may be time to replace the gears and belts. They are a wear part on the AVID.

Thanks for the tips everyone. I tried adjusting the spring tension and it didn’t make a recognizable difference :unamused:

I’m afraid my rack/pinions could be worn. I have been in the camp of not greasing the racks - I think Avid suggests it isn’t necessary. I’ve had this machine for less than a year. It does get alot of use but not like, continuously 8 hrs a day every day. I’d be surprised if they wore out that quickly without there being something wrong? I do understand that grease is good and will grease them moving forward. How often do you all have to replace them?

Don’t grease the racks. It’s just makes losing steps easier and doesn’t improve wear rates.

You can just eyeball the pinion gear and see the wear.

If you are using the machine 8 hours a day 5 days a week then yes, about a year or so to wear through a pinion gear. Take a picture of one of yours from the Y axis and post it.

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There’s the pic. I guess it looks pretty worn?

It is hard to tell from a single view of it. If there are steps cut into the gear teeth then that will introduce backlash. It looks like it should be replaced soon but can also be the way the light is hitting it.

The pinion gear and the bearings are consumables for these machines so this is normal.

You will find they do wear unevenly. This is due to how you assembled the machine, the natural bow and bulges to the 8020, etc.

Small price to pay for a monster sized machine though. The rack and pinion design is superior to the bicycle chain machines in accuracy and speeds but at the cost of those pinion gears wearing out.

Be sure to put that in your spreadsheet when figuring out your hourly cost! You don’t pay for that stuff, your customers do.

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