Kobra S1 Max + ACE 2 Pro — 11511/11512 during filament changes, cutter not fully cutting?
Posted in some other similar communities but trying to get more visibility.
I’m troubleshooting repeated 11511 and 11512 errors during automatic filament changes on my Anycubic Kobra S1 Max Combo with ACE 2 Pro.
The issue appears specifically during the cut/retract portion of the filament change, rather than normal feeding.
What I’m seeing
ACE 2 Pro can feed filament all the way toward the extruder.
Filament can also retract through the PTFE path.
During an automatic filament change, the printhead moves to the front cutter position.
It appears that the filament is not being completely cut before the ACE begins retracting it.
Instead, the ACE seems to pull against filament that is still partially connected at the hotend/extruder.
This creates significantly more resistance than a normal retraction.
I’ve subsequently gotten both:
11511 — abnormal feeding
11512 — abnormal retraction
I’ve also seen the filament buckle/accordion inside the return detection/buffer area/4&8 channel port, which initially made me think the return detection module itself was the problem.
I have already:
Cleared the affected filament channels.
Inspected/straightened the PTFE routing.
Made sure the ACE 2 Pro is level and the tubing isn’t entering the system at severe angles.
Cut fresh filament tips and reloaded them.
Confirmed the ACE can physically move filament forward and backward.
Confirmed filament can reach the PTFE tubing immediately above the extruder.
This happened a few times initially but chalked it up to being a noobie and stuck to single colors for a while. But would still happen if I completed one print and then tried to do another after.
Then I really dug into it during a multicolor Gridfinity print. The first material printed normally, but when the printer attempted the planned color change, the problems started.
Also tried to do a pyramid 4 color print to check. It got through all of it but when it returned to first/initial spool I was able to reproduce the issue. Although, I’m getting tired of having to do a full disassembly every time I complete a print and mitigating by never returning to the same spool.
Current suspicion
I came across reports suggesting that on some S1/S1 Max machines the printhead may not be traveling far enough into the cutter-actuation position, resulting in only a partial cut.
That would explain my symptoms:
partial cut → ACE retracts → filament is still attached → excessive retraction force → filament buckles or fails to clear the return sensor → 11512/11511
I’m now trying to determine whether the cutter is actually receiving its full mechanical stroke when the printhead moves into the cutting position.
Questions for other S1 Max owners
Has anyone experienced this specifically on the Kobra S1 Max Combo?
If so and apologies for being a bit of a novice here but:
Did you confirm that the printhead wasn’t moving far enough to fully actuate the cutter?
What X/Y position does your machine reach during the cut?
Is there a safe way to adjust the cutter/impact position on the stock firmware?
Is the cutter position controlled by firmware, machine configuration, or Slicer Next?
Did this begin after a firmware update?
Has anyone solved it without installing custom firmware?
Is there a good test procedure for confirming a complete cut before letting the ACE retract?
I don’t want to arbitrarily increase the X position and potentially slam the carriage into its physical limit, so before changing anything or with my luck and frustration breaking anything — looking for some guidance from my fellow redditors. Again — I’m a bit of a novice but my day job is based in the sciences so with a little helpful nudge I’m hoping I can resolve this once and for all and simply enjoy printing nonsense. Lol thanks everyone!