Solved Wobbling Along Y Axis

Picture attached. The X and Z axes look great, but Y is inconsistent. What steps can I take to improve it?

This printer came with a broken Y tension which I fixed which meant re-attaching that belt myself. It's notably tighter than the X belt. Would that be causing it, or is over-tightening not really an issue?

 

I found the big bolts/nuts were loose at the bottom and tightened them, and I loosened the y belt... but based on this latest print, I’m more confused than ever about what the real culprit is.



You can see that, for the most part, the shift in layers directly correlates with a change in the layer components. You can see that the whole print jerks to the left (Y+) when the window at the back of the benchy starts - then as it builds up, it drifts right right toward Y- as the window is created - then it jerks back to the Y+ again when it finishes. It seems like every jerk is associated with a significant change in layer shape compared to the one prior.

Again, it seems to only affect the Y axis; the X axis is imperfect but far more acceptable.



I have the threaded rods (lead screws are on order) but can’t believe that that would be the explanation for this given it’s limit to just affecting one axis.

 

So other than tightening the bolts/nuts and re-tightening the Y belt, which I did, what should I mess with?


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The big ones on either side of the motor that the belt rubs along? Yes - they were both a bit loose, so I tightened them as much as I could. It might have helped a little bit but it obviously still needs improvement.


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I did notice that it had insane acceleration compared to my other printer. I’ll try lowering that - I feel like I tried that in the past with no luck, but I’ll give it another go tomorrow.

If it’s relevant, I’m slicing with Cura for Robo (Cura 2.5) and printing via Octoprint.


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What numbers do you recommend for acceleration and jerk adjustments?


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So overnight I ran a Z-wobble test print with nearly identical settings to the benchy print. Minor ribbing aside (and the zits, a separate issue I’ll inquire about elsewhere) I think it looks substantially better than the benchy. Does this have any effect on your opinion of what adjustments I should be making?

There IS a tilt at the bottom for a few millimeters but it seems to go away.

So confused.




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One thing I just remembered is that when I got this printer a couple years ago (it gathered dust for a while), it had a broken Y tensioner which I Krazy Glued back together. I'm not sure if that's related, but i'm printing some new tensioners right now and will see if switching to that helps.

 

Replaced the tensioners and redid the belt, that did no good.

Changing the acceleration made a huge difference though: I changed the default X/Y to 600 and the max to 800, and this is the difference (left is after belt change, right is after acc change).



I’m still not happy with the overall quality yet, but at least I’m not completely maddened by it. Y is still definitely worse than X too, though less prominently.

I noticed that there’s an inconsistent amount of friction felt when I move the bed by hand. I’m not sure if that’s common when the motor is off or if that indicates some other hardware issue to look at.


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Man, I sure wish I'd been this persistent two years ago instead of shelving the printer back then - then maybe I could have used some warranty support

I'll order some bearings to arrive early next week and try those. There are some on the Z rods too, correct? I may order a dozen just to make sure I have enough for the future.