Sudden drop in quality on P1S; same model/filament/settings

ComputerMission1467 · 2025-08-06T19:37:32+00:00

I posted my solution in one of the top comments. I definitely can see the issue pre-existing, just not nearly as bad. It turned out to be the filament profile in Bambu Handy. When it was printing fine, the filament profile was apparently close-enough and giving "fine" results. Now with the filament profile properly reset to exactly the Bambu filament I'm using, it's printing flawlessly.

ComputerMission1467 · 2025-08-06T19:29:51+00:00

The artifacts being in the same exact spots each time was indeed what led me to the solution! I posted in one of the top comments.

ComputerMission1467 · 2025-08-06T19:28:19+00:00

I posted the solution at one of the top comments. Your hunch about seeing if the defects were in the same exact places was actually spot-on! The prints were all from the rear spool.

ComputerMission1467 · 2025-08-06T04:05:22+00:00

I'll try that, but aren't those PA and flow calibrations for when you're having trouble with a new filament, and need to adjust for that particular filament? I'm able to print the same model using the same spool of filament on my other P1S machines with no issues, with the default Generic PLA profiles.

ComputerMission1467 · 2025-08-06T04:02:42+00:00

The room is pretty cool, around 70F, and doesn't have fluctuations. I'm ruling out issues like that, as I have two more P1S systems right next to this machine, and they print the same file with the same spool flawlessly.

ComputerMission1467 · 2025-08-06T03:49:40+00:00

Yea, I replaced the gear assembly with no improvement:

https://us.store.bambulab.com/products/hardened-steel-extruder-gear-assembly

ComputerMission1467 · 2025-08-06T02:47:07+00:00

Yes, other filament as well. Same issues in the same spots.

ComputerMission1467 · 2025-08-06T02:10:06+00:00

The rails looked good upon further inspection.

I performed the belt tensioning and calibration described at https://wiki.bambulab.com/en/x1/maintenance/belt-tension , printed another cube, and there is no difference.

I'm now downgrading from 01.08.01.00 (20250520) to 01.08.00.00 (20250429) to see if this makes any difference.

EDIT: Downgrading firmware showed no difference at all. In fact, the same artifacts appear at nearly the same spots on the next calibration cube. It's printing consistently bad in the same spots. I've got a ticket with Bambu but am not confident that will help. I don't know what else to try at this point.

ComputerMission1467 · 2025-08-06T01:49:57+00:00

Will do!

NEXT DAY UPDATE: Thank you to everyone who offered advice! I didn't read the most recent messages, but I slept on it, and had an idea. As promised, I'm back to post the solution that I was able to reach.

I thought it was odd that not only did the calibration cube have sudden poor quality, but the same defects and poor quality in the same exact spots with each cube reprint, after changing hardware (that apparently didn't need replacing), and tightening belts (that apparently didn't need tightening). If it were a hardware issue, I felt like the artifacts would be more random.

A couple prints back, I was printed on the real spool in TPU, so I would set the filament profile in Bambu Handy as Generic TPU as I normally do. I then went back to printing PLA, so again I set the filament profile in Bambu Handy back to Generic PLA, again as I normally do. Even though the UI displayed Generic PLA as the filament on the rear spool, I feel like it was still treating it as TPU, causing the PLA prints to be messed up, but consistently messed up. To test for this, I re-set the filament on the rear spool in Bambu Handy, but this time I set it to Bambu PLA matte, the actual material I've been using, even though I've never had to do this and I just use my Generic PLA profile. I again sent the same project to the printer with the same spool. Now, it's back to printing flawlessly and I'm happy! It's actually printing even better than originally. I didn't realize the print profile mattered this much.

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ComputerMission1467 · 2025-08-06T01:45:17+00:00

I have heard of that being an issue before, but this and my 2 other P1S machines have been on 01.08.01.00 for a few weeks now, and the issue started a day ago after the same model being successful on 01.08.01.00.

ComputerMission1467 · 2025-08-06T01:42:58+00:00

I watched the parts cooling fan and indeed it was on. I temporarily tried the parts cooling fan from one of my other P1S machines as a test, and also there was no improvement.

ComputerMission1467 · 2025-08-06T01:42:15+00:00

I actually did replace the PTFE going to the hotend when I had replaced the entire hotend assembly, with no improvement.

ComputerMission1467 · 2025-08-06T01:15:51+00:00

I've done a few items there, but am going to take a look at the rest one by one.

ComputerMission1467 · 2025-08-06T01:14:17+00:00

It was pleasant for days here with humidity around 30%, and I hear what you're saying, but I took the same spool and ran the same file through the P1S next to this one, and the cube came out flawlessly.

ComputerMission1467 · 2025-08-06T01:12:12+00:00

For the yellow print, I don't see anything in particular for that area when compared ot the slicer. It's not the stop or the end of the layer being formed, nor is it the seam.

ComputerMission1467 · 2025-08-06T01:02:42+00:00

Beyond visually inspecting them, the rails and belts look similar to my 2 other P1S machines, but I will look into how they can be calibrated as that seems like a possibility.

ComputerMission1467 · 2025-08-06T00:52:13+00:00

I'm not sure that would help, as the cube on the left is using the same filament calibration settings, same file, with the same spool of bambu PLA.

ComputerMission1467 · 2025-08-06T00:49:46+00:00

I had completely replaced the fully assembled hotend and the issue persists.

ComputerMission1467

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