When asking for help, please provide as much information as possible about your inquiry.
This will help everyone to better understand your problem, and provide you with the best solution.
- Detailed description of the problem
- Printer model used
- Slicer settings used
- Type of filament used
- Photos that clearly show the problem
- .3mf file (if the file can be shared)
- Any potentially useful information that is related to the problem
Hi everyone,
I’m trying to diagnose a surface quality issue on my A1 Mini and I’m running out of ideas, so I wanted to ask if anyone has experienced something similar. The printer is brand new, I ran every single calibration test twice and the issue persists.
Problem description
When printing flat pieces, the printer leaves small spikes or sharp bumps on the surface. They are sharp enough that you can feel them when touching the print, they even hurt your finger a little.
Observations:
-
The spikes appear when the nozzle lifts and starts a new line.
-
Long straight lines print perfectly.
-
The spikes appear at the start of new segments / direction changes.
-
During the final top layers the nozzle partially melts them, but the surface still ends up textured and spiky.
It looks like a small blob of plastic is deposited when extrusion restarts.
Printer / settings
Printer: Bambu Lab A1 Mini
Slicer: Bambu Studio
Material: PLA
I tested with multiple PLA filaments and the behavior is the same.
Temperature tests:
Cooling:
Layer options tested:
Retraction tests:
Flow tests:
- Flow ratio adjusted (0.96 → 0.94)
Speed tests:
- Reduced outer wall speed and top layer speed
Other checks:
-
Nozzle inspected and cleaned
-
Silicone sock correctly installed
-
Different filament spools tested
Important observation
The spikes appear exactly when the nozzle lifts and then touches the print again to start a new segment.
They do not appear during continuous straight extrusion.
This makes me suspect something related to:
Has anyone seen this behavior on the A1 Mini or found a setting that fixes it?
Any ideas would be greatly appreciated 
1 Like
I am afraid I only ever see such heavy stringing with PLA with soaked filament. Blobs and flow dynamics issues fit with that.
After weeks at sea, all filament must be considered moist as the bags still allow moisture through.
Best to make it a habit to dry new filament before looking at settings. Even if it is just to rule it out.
& 
I will do that, I will set the filament to dry overnight now and try again tomorrow morning. I will update the results. I’ve tried at least 5 different spools, and 3 different colors so far and still got the same result. I tried those filaments on my other printers, I have a CR6-Se and an Ender V3 Ke and they worked fine. This is my first BambuLab, is it possible for the filament to work fine on the others but still have moisture issues with the Bambu? To have that in mind for future prints too
1 Like
+1 for dry
A simple test is to heat the nozzle to 210 and extrude. The moment When the gears stops, cut off the molten strand. If your filament keeps happily coming out of the nozzle, more than say, a millimeter or two, then she is wet and needs dry. Bonus points of you see steam. This test won’t always catch mild issues but it will always catch extreme moisture issues.
1 Like
I’ll have that in mind too, thank you! Now that you mentioned it, one of the spools I used on my KE steamed a little when I tried it. The print came out fine, but that means it was wet for sure. I set a yellow 3N3 PLA filament (the brand I usually use) to dry and will try the same model and settings tomorrow, I’ll keep you guys posted, thanks!
1 Like
Yes, especially when compared to slower printers. Amongst other effects, moisture changes the flow and cooling behavior of the filament so faster deposition and lower layer times run into moisture induced increases in oozing and cooling times pretty quickly.
&
Hello! I just finished printing the same file, same settings as before but with the dried filament. I switched to yellow for a change, dried it for 8hs and still the result is the same 
When I did the calibration for the flow the little rectangles looked just fine, no peaks or bumps at all, any ideas on what it could be or suggestions on what to look for?
Well, the next step would be to revert all settings back to either generic defaults or manufacturer specifications (please post if you have them) to have a clear reference and only change key parameters for a very good reason. (Note: From your first post we know that you changed a lot but not what your settings were for the yellow sword)
And of course do the Flow Dynamics (!) calibration rather than the flow calibration.
On a small print like this, I’d print several at the same time to avoid minimum layer time issues, use Arachne and adaptive layers down to 0.08 or even 0.04mm.
A concentric pattern for top surfaces may aid a cleaner appearance as well.
&
I just reverted all the settings to the default profiles both for filament and printing settings. here I attach some pictures. I changed to concentric pattern to try, but got the same results. I also lowered the filament temp from 220 which was the default to 200
The supports are turned off. Here are the settings for the filament
I tried printing a small cube, just to try something different and it came out super nice, no peaks no lines or bumps, using these same settings. I also tried scaling the model to 150% and it still looked exactly the same. I will try the arachne and adaptative layers and check how it goes.
Look! It improved a little bit! The peaks are mostly at the tip of the blade now and the center is a little smoother. I checked the nozzle again just in case but I see nothing strange, no filament stuck and no weird looking tip. Any advice on which other setting to check? I’m so happy that it’s finally improving, thank you!
1 Like
If you’re able to, sharing the 3mf would be nice so we could slice it and inspect the preview.
Or send a screenshot of the slicer’s “Line Type” preview showcasing this same area. Everything so far that you’ve shown looks within normal, aside from unknown flow dynamics [k factor, pressure advance, all of these are the same thing diff name]
2 Likes
Sure! Here is the 3mf
Needle.3mf (966.5 KB)
This is how it’s looking when I slice it. Can you please tell me a little more about the flow dynamics? I calibrated it once, but as I’ve been touching everything so much I’m not sure anymore
Excellent 
Glad you are getting some success. 
I myself try to change fundamentals like nozzle temp or cooling as little as possible and as late in troublehooting as possible as I have made the experience that they frequently open Pandora’s box by the law-of-unintended-consequences. For example viscosity changes from low temps…
Did you do the Flow Dynamics calibration? That usually takes care of line start and stop issues. In some cases, enabling “wipe on retract” can be a life saver but I’d keep z-hop disabled.
And of course, afaptive layer lines will have a big impact on quality
&
I did it once, maybe I should do it again since I’ve been touching things here and there?
1 Like
The top surface of the needle is really uneven and making the extruder do lots of small actions, so not exactly an ideal model - it’s gonna look a little uneven and “turbulent” from all those small paths.
That being said, the machine should be able to do it. I think you should redo flow dynamics / k factor.
1 Like
Sure. Flow dynamics is pretty important as the moment the extruder starts (or stops) pushing material is not the same moment the pressure in the nozzle builds (or ceases). There is always some lag in the response. Therefore, if this is calibrated, this lag can be taken into account in the slice.
But the wiki does a much better job of explaining it 
Flow Dynamics Calibration | Bambu Lab Wiki
&
How do I post a new topic here - I can’t see any new post button anywhere
Bambu Silk+ (which shows defects pretty well and is more prone to stringing) on my H2C, auto-calibration, Arachne, concentric top and bottom, rectilinear infill
I did cheat on the adaptive layer height though. In the Machine Settings (hover the mouse over the top left printer icon), tab Extruder, I set a minimum layer height of 0.04mm with the .4mm nozzle used.
&
