Tilter/skewed belt? - Hardware, firmware and software help

RE: Tilter/skewed belt?

abmantis — Sat, 27 Dec 2025 22:30:44 +0000

Yeah, maybe it has no impact. But the Core One already suffers from VFAs, so I don't want it to be an extra possible cause.

Yep, support is sending a replacement for the belts. :)

RE: Tilter/skewed belt?

Jürgen — Sat, 27 Dec 2025 22:22:20 +0000

Posted by: @abmantis
I can't say for sure, but it could cause VFAs (or aggravate them) since the belt has an uneven surface.
Prusa's support also mention that it could cause noise issues from resonance.

I wouldn't be too concerned about a quality impact. As it is approaching the idlers or pulleys, the belt will gradually twist back into vertical alignment, I guess. And that torsional vibration mode exists in any belt, even if its position at rest is vertical.

But anyway -- if you have been in touch with Prusa support about this, I hope they will send you replacement belts?

RE: Tilter/skewed belt?

abmantis — Sat, 27 Dec 2025 21:27:26 +0000

I can't say for sure, but it could cause VFAs (or aggravate them) since the belt has an uneven surface.

Prusa's support also mention that it could cause noise issues from resonance.

RE: Tilter/skewed belt?

Jürgen — Sat, 27 Dec 2025 20:35:05 +0000

What would be the impact of a belt with that slight tendency to twist? I am not sure it is detrimental in any way. Do you see or expect an effect on print quality, acoustic noise, wear?

RE: Tilter/skewed belt?

abmantis — Sat, 27 Dec 2025 19:39:12 +0000

After disassembling the print head, I can confirm that the belts are defective. Even when not under tension, it bends at that exact spot. The lower one also has a slight bending, but less pronounced.

RE:

abmantis — Fri, 26 Dec 2025 22:37:23 +0000

I think I may have a bad/faulty pulley. I've moved the print head all the way to the back, and moving it left/right the "tilt" moves along with the belt, so it is not a problem just between the print head and the left idler. In the following two videos it is very clear:

https://storage.googleapis.com/prusa3d-content-prod-14e8-wordpress-forum-prod/2025/12/d63a25db-20251226_220117.mp4

https://storage.googleapis.com/prusa3d-content-prod-14e8-wordpress-forum-prod/2025/12/00f01e67-20251226_220033.mp4

Tilter/skewed belt?

abmantis — Fri, 26 Dec 2025 17:02:46 +0000

When I move the print head to the front right side, the top belt on the left side of the print head tilts forward on the mid section. Both ends of the belt (on the print head and on the pulley) seem straight, but the mid section bends/tilts forward a bit.

Any clue on what it may be? I've checked all pulleys and the belts are not too far up or down on them. The only thing I've not yet checked is the belt assembly on the print head, since that is quite some work to disassembly.

Any other ideas on what may be causing this?

It is hard to show on photos. On the photo with the yellow markings, the belts were a bit looser than normal, since it makes it easier to show the issue.