Bambu A1 with AMS Lite: Poor overhang quality compared to standalone A1

Bambu Lab A Series Bambu Lab A1 mini
1

Hi everyone,

I’m running into an overhang issue specifically on one of my Bambu Lab A1 printers—the only one paired with an AMS Lite.

Using identical slicer settings, filament, and print profiles across all my A1 machines:

  • The standalone A1s print overhangs cleanly with zero issues.

  • The A1 with AMS Lite consistently produces poor, sloppy overhangs on the exact same model.

What I’ve already tested/ruled out:

  • Extrusion / Dynamics: Re-calibrated Pressure Advance / K-factor (no noticeable change).

  • PTFE routing: The AMS Lite is wall-mounted to ensure smooth tube curvature and minimize drag.

Since the slicer parameters are identical, I’m trying to isolate what the AMS Lite setup might be introducing—extra toolhead drag, partial feeding resistance, or something mechanical.

Has anyone encountered this specific discrepancy with the AMS Lite, or have ideas on what to inspect next?

Thanks in advance!

2

The AMS lite only pushes filament to the extruder during a load sequence - after that it’s the extruder gear doing all the pulling.

I’d suggest trying your AMS Lite on your other A1 machine just to verify that it’s actually the AMS and not something with the machine itself.

3

I made a test without the AMS, connecting directly the filament and it worked just perfect. I think the issue is related to the AMS Lite. As I said, I tried to calibrate the K factor but the result is not giving me better prints.

4

Ok, does the issue happen across all four spindles?

Are you using Bambu spools are something else?

How long have you been running the AMS, and when was the PTFE tubing last replaced?

Is the PTFE tubing actual Bambu-supplied tubing or something else?

5

Ey, thank you for the reply.

Yes, all the tubes have the same issue. That’s why I decided to put the AMS on the wall but the result is the same.

I’m using Esun spools.

I don’t use too much this machine in particular so the AMS Lite is practically new. Original PTFE tubes.

Maybe I could try to re calibrate the K factor. I noticed that with the new position for the AMS Lite, the value changed from 0.025 to 0.035.

6

Messing with K factor is only ever going to be a bandaid, not a solution. Do whatever you want, but at best you’re masking a problem.

Which adapters are you using for your eSun spools?

Have you tested any Bambu filaments on the AMS Lite to see if the issue remains?

7

There is one possible cause, but it’s about as rare as being struck by lightning. Still, in very specific situations - especially when the AMS is mounted on a wall - it can happen.

Filament always contains a tiny bit of moisture, even when it feels completely dry. When it melts, that moisture turns into water vapor. Normally, the amount is so small that it doesn’t affect 99.99% of users, because the vapor simply disperses through the tubes without causing any trouble.

However, if the AMS is positioned in a very unfavorable way, the water vapor can collect instead of dissipating. In that case, the tube system might unintentionally act like a funnel, directing the moisture, or, to be precise, that accumulated cold water, toward the printers nozzle.

As I said, this is extremely rare - it practically almost never happens. But if your AMS Lite is mounted higher than the printer, it at least becomes a possibility. This only applies to the AMS Lite, though. The other AMS models have a heating function that evaporates moisture before it can accumulate.