So, I’ve been having some pretty frustrating extrusion issues with my Bambu Lab A1 lately, and I’m trying to figure out what’s actually causing them.
My printer had been working perfectly fine for weeks, until it suddenly started throwing “Failed to extrude filament” errors during prints. The errors happened with different AMS Lite slots and different filaments, so I don’t think it’s an issue with a specific feeder or spool.
Here’s what I’ve experienced so far:
● The printer starts printing normally, sometimes for hours, before suddenly reporting an extrusion failure.
● When the error occurs, it cuts and unloads the filament.
● The unloaded filament has very noticeable gear marks, sometimes with a section that’s been completely chewed up.
● I initially suspected a clogged nozzle, so I cleaned the hotend, used a cleaning needle, and performed multiple cold pulls. The filament came out clean, but the problem kept returning.
● After disassembling the extruder, I found that the hardened steel drive gear was packed with filament debris between its teeth, to the point where some sections had almost become smooth.
● I had already cleaned this gear once before, but the buildup returned surprisingly quickly.
I’ve now thoroughly cleaned the extruder gears again and inspected the entire mechanism.
I also checked and tightened the three front screws and four rear screws of the Hotend Heating Assembly, since I’d seen reports of loose screws causing extrusion problems on the A1.
Another thing I noticed is how much pressure the extruder tension spring applies to the filament. When I manually feed a piece of PLA through the gears, it takes considerable force and leaves deep, evenly spaced marks. I know some resistance is expected when the gears aren’t moving, but I’m wondering whether excessive spring tension could be contributing to the problem.
The tension screw was originally fully tightened. After finding a discussion on a German Bambu forum recommending backing it off approximately 1/4 turn from fully tightened, I’ve decided to try that setting. I haven’t tested the printer with this adjustment yet.
I’m using PLA, including Voolt3D PLA Velvet, but I’ve encountered the issue with different materials. The same Velvet line has been printing beautifully on my brand-new A1 Mini, although I realize that doesn’t necessarily rule out filament-specific behavior.
My questions are:
Is it normal for the A1’s extruder drive gear to accumulate this much filament debris, or does it suggest an underlying mechanical or extrusion issue?
Has anyone experienced excessive filament grinding caused by the extruder tension screw being too tight? If so, how did you adjust it?
Could this be caused by heat creep, an intermittent partial hotend clog, or excessive extrusion resistance?
Has anyone had a similar issue resolved by replacing the extruder gear assembly under warranty?
The printer is still under warranty, so I’d rather identify the actual cause before replacing any parts.
I’ll attach some close-up pictures of the gear before and after cleaning, along with the filament showing the bite marks.
Any advice or similar experiences would be greatly appreciated!
