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Tilter/skewed belt?  

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abmantis
(@abmantis)
Active Member
Tilter/skewed belt?

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.

 

 

Posted : 26/12/2025 5:02 pm
abmantis
(@abmantis)
Active Member
Topic starter answered:
RE:

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

 

Posted : 26/12/2025 10:37 pm
abmantis
(@abmantis)
Active Member
Topic starter answered:
RE: Tilter/skewed belt?

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.

Posted : 27/12/2025 7:39 pm
Jürgen
(@jurgen-7)
Noble Member
RE: Tilter/skewed belt?

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? 

Posted : 27/12/2025 8:35 pm
abmantis
(@abmantis)
Active Member
Topic starter answered:
RE: Tilter/skewed belt?

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. 

Posted : 27/12/2025 9:27 pm
1 people liked
Jürgen
(@jurgen-7)
Noble Member
RE: Tilter/skewed belt?
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?

Posted : 27/12/2025 10:22 pm
abmantis
(@abmantis)
Active Member
Topic starter answered:
RE: Tilter/skewed belt?

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. 🙂

Posted : 27/12/2025 10:30 pm
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