Y Lead Screw Vibrations

Alright guys and gals. I need some assistance here. I have noticed a heavy vibration while the router is moving rapidly through the middle third of the Y lead screws (front to back and back to front). I don’t notice it during cutting but then again it doesn’t usually move as rapidly or the other noises drown it out. There is no vibration as the carriage moves near either end of the Y rails. Is this possibly an issue with the backlash nuts being too loose or tight? Or maybe the couplers for some reason. I would really like to get this solved because I cringe each time I hear it. I haven’t tried adjusting the backlash nuts yet and the couplers are tight. Any help or thoughts appreciated.

When the Longmill is running, watch the leadscrews and see if they wobble while in motion. When the machine is doing rapid movements, the leadscrews can “whip” which can cause intense vibration. Make sure the leadscrews are placed under tension by snugging up the ACME locking nuts and confirm that the v-wheels are adjusted to hold firmly but can still be rotated by hand.

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Thanks Scott. I will double check the lead screws and acme nuts and couplers (again) to make sure all is tight, snug and tensioned. As for the V wheels I have had an ongoing issue with them being too tight. I can adjust to being able to turn them but when I tighten down the M5 screw they get too tight again. I’m thinking about pulling the adjustable ones and eccentric nuts and cleaning out the paint in the Y carriage holes. The eccentric nuts were pretty tight when I assembled the cnc so that may be an adjusting issue. Should have done that putting it together.

I had the same issue - did take some fiddling with the concentric nuts to reach that point of “tight but not too tight”.


I had the same issue to the extreme. It bound the Y axis on the right side and misaligned the X-axis gantry. I fiddled with the concentric nuts and backlash then Andy suggested to loosen off the screws holding the backlash nuts , run the gantry up and down in the Y axis, then snug them down.
The wobble was gone and there was no more binding.
Seems to have helped.

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