Bent rods!?

[destroyer2012 0]

So I've had my UM for about a month now and I've been printing stuff for about 2 hr almost every day, but recently I've noticed a ticking sound while the UM is working, almost like a wood settling noise. I thought nothing of it, oiled my rods etc, but now I noticed that the left Y axis block (the moving block attached to belts which holds the cross bar that the head is mounted to, on the left side) is actually moving up and down as i move the head back and forth along the y axis by hand.

SO just to clarify what I'm doing, I am moving the head parallel to the cross bar that I'm accusing of moving up and down. As I move the head by hand I can see the axis block which is not moving sideways (stationary axis) move up and down as if the rod it's on is wobbling up and down, about half a millimeter total travel. This corresponds with the ticking noises I mentioned; must be some wooden part is shifting as the cross bar is being bent out of shape by the wobbling rod.

As far as I can tell it's because my rod is slightly bowed. I haven't taken my UM apart yet to ascertain if that is the case for sure but it's the only explanation that makes sense. The question I want to ask is, has anyone else experienced this? What could cause those rods to become bent? I didn't realize I could pull the belts tight enough to bend the rods, maybe that happened? If that is the case, UM you guys better get on this belt tensioning thing! It sucks, and could cause severe damage to the printer if done wrong!

[Daid 306]

I don't think you could have bent the rods. Is there a chance that it was bent to begin with but you only notice now?

[destroyer2012 0]

I don't think you could have bent the rods. Is there a chance that it was bent to begin with but you only notice now?

It is possible it was bent to begin with, however, I do not remember what it was like to begin with so I am left with potentially bent rods NOW.

I really hope I didn't bend the rods.. I am struggling to see why else that axis block would move like that though. Perhaps my bearings are asymmetric somehow, or the belt pulleys are torquing the rod? I tried loosening all four of the belt pulleys for the y axis and the up and down motion was still there. The rods were still turning with pulleys loosened though, so it is still consistant with bent rods.

When I get home I'll take it apart and see. Maybe it doesn't matter but I can only see this problem getting worse over time. Not to mention this might be the reason why my axes don't move as smoothly as they should.

[technicality 0]

Check if the holes in the pulleys are truly centered too, they could account for varying belt tension (meaning varying friction) and maybe even some kind of wobble?

[destroyer2012 0]

The rod is definitely bent. Whether I bent it or it was bent to begin with I don't know but it seems to be bowed out in the middle by about 0.2 mm. That means the axis block goes up and down by 0.4 mm as the head travels to the +X. The head probably moves up and down a lot less by lever action, but potentially a non-negligible amount when doing really thin layers.

I'm probably just going to disregard it for now because printing at 0.2mm works with no problem. But just a heads up guys: Check if your rods are bent. It could be responsible for why your axes are so hard to move.

I loosened the belts just a bit and applied some foosball table lubricant to allow my axes to move better. Also re-squared everything again. The wobble is still there but I think it is affecting my travel speed much less now.