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
I appreciate any help:
I bought a Bambu Lab P1S, and I set it up, I ran a calibration, and used the provided PLA basic filament that came with the printer to do the Benchy print, and I printed the stock Benchy file that comes with the printer. However, the printer sounds very loud, and its movements sound very erratic. There’s no squeaking, but it does sound pretty loud. And when the Benchy gets to around the 18 millimeter mark, it’s happened twice now, or three times now, where it stops printing right. it’s as if the print shifts. It continues printing, but after layer 18,or after the 18 millimeter mark, whatever, it starts printing like it’s shifted back and into the bed more. So it goes further to the back of the printer and to the right. And it’s as if it’s like shifted the print location. It’s happened twice now at the exact layer where it moves, it’s as if it just shifted right. It moves, it continues printing the boat, but it prints it too far toward the back of the print bed and too far to the right. So it shifts it back and to the right. I’ve tried recalibrating it… i tried retensioning the belt and even cleaning carbon fibre rods with IPA and microfibre. no luck so far.. its a new printer literally bought it today. Again, I appreciate any help
Sounds clearly like a defective unit. When the shift is diagonal , probably one motor has lost steps for some reason.
File a ticket with support. Easiest way in my opinion is the mobile app. It will append the log file automatically so that support can analyse what went wrong. They typically want to see a picture or video, so you can shorten the process when you directly append one to the ticket.
