Hey everyone,
I wanted to share an experience I recently had with my Bambu Lab P1S – maybe it helps someone or sparks a good discussion.
I was having minor print quality issues for a while – nothing dramatic, but just subtle inconsistencies in surface quality and layer alignment. After checking the usual suspects, I started looking at the belt system, especially the XY belts.
Like most people, I had both belts tensioned evenly and pretty tight, as generally recommended. But then I noticed that the gantry wasn’t sitting perfectly square on the Y-axis rails. Some forum posts suggest that slight differences in belt length or routing could cause this, especially in CoreXY systems.
So I manually squared the gantry using a right-angle tool, and interestingly – after doing so, the belt tension was no longer equal. I decided not to re-tension them evenly, and instead kept the gantry perfectly aligned.
And guess what?
Print quality improved noticeably.
Even at higher speeds (up to 250 mm/s), the results were cleaner and more consistent. I suspect that having both belts too tight – and equally tight – may have introduced mechanical strain or slight misalignment that impacted accuracy.
So here’s my question to you all:
Has anyone else had a similar experience?
Do you think it’s better to prioritize gantry alignment over perfect belt symmetry in a CoreXY setup like this – even if that means the belts have slightly different tensions?
Thanks for getting back to me! Just to clarify – I’m only talking about the XY belt system, not the Z-axis or anything else.
I’ve been experimenting a bit with belt tension and trying to dial in the ideal balance. What I found is that when I align the gantry square to the Y-axis, the belts don’t have exactly the same tension – probably because the belt lengths aren’t identical. Strangely enough, when I avoid over-tightening and instead let the gantry stay square with slightly different tensions, my print quality improves.
Most forum posts I’ve seen always recommend tighter belts as the solution to quality issues, but in my case that seemed to make things worse. So now I’m testing softer tension with a straight gantry to see how it behaves.
I’m wondering if others have tried this and what their experience is. Also, could there be anything else that affects print quality in this setup that I might be missing?
Maybe when the tool head movement is in that direction, one belt has more tension than necessary, like, stretching the belt a little bit every time each tooth bites on the idler.
I just don’t like how the teeth rub against smooth idler. It screams out trouble for what I see
