H2C purge problem

Bambu Lab H2 Series
1

Hello To H2C owners

My H2C printer isn’t priming properly when I start a print with the left extruder (external spool). It’s not priming Line properly and the filament isn’t feeding correctly. However, with the right extruder, there are no problems the priming line is correct.

Have you also experienced this problem?

Cordially

2

Did you get any resolution to this? I’m also having a similar problem where the purge line doesnt come out, just a couple of blobs and then the first line of the print is under extruded. Its completely find after that so it doesnt seem like a clog. This seems to be happening on every print.

3

I’m also having this issue. Any updates on fixing this? @JordanKendrew @Flolly_Factory

4

I too am now having this issue seemingly out of the blue. Everything has been fine for weeks, but now my left nozzle isn’t printing the purge line (even though it tries) and filament doesn’t seem to come out until about ~5 seconds into the print.

5

Do you all have the problem with external spool? If so try to reroute the PTFE tube to the external opening without the buffer and feed from there.

6

I am having exactly the same issue lately. Have you found a solution ? I have checked the extruder gear and everything, but nothing it jammed. And the PTFE tube of the left nozzle is the shortest of both, so I don’t think this is the issue.

7

Same issue when I feed PA6-CF/PPA-CF to the left nozzle via external spool. I have to enable a 2 or 3 loop skirt to make sure I have filament when the print starts.

8

Same problem here.

But it sounds like the cause or solution has kot been found?

I already opened the extruder, cleaned the gears (even while they were definitely not that dirty), and cold pulled all my nozzles. Nothing helped.

9

Did anyone ever figure out a workaround for this? I’m running into the exact same issue on a brand new H2C. Whenever I start a print with the left nozzle, it tries to lay down a purge line, but no filament comes out for the first 5 seconds or so.

10

Just wanted to follow up here since I got it sorted out. I ended up adding a conditional check in the machine start G code to bump up the prime distance specifically for the left nozzle.

Because the left side uses that separate lifting mechanism, it seems to need a bit more extrusion at the very start to build pressure compared to the right side. Bumping up the initial prime values right in the slicer fixed the blank start completely.

You want to find this original section in your Machine Start G-code (under the nozzle load line part):

G1 E5 F{filament_max_volumetric_speed[initial_no_support_filament_id]/2.4053*60}
    G1 X290 E10 F{filament_max_volumetric_speed[initial_no_support_filament_id]/2.4053*60}

And replace it with this conditional block:

{if initial_nozzle_id == 0}
    ; --- LEFT NOZZLE: Increased prime to fix startup delay ---
    G1 E12 F{filament_max_volumetric_speed[initial_no_support_filament_id]/2.4053*60}
    G1 X290 E14 F{filament_max_volumetric_speed[initial_no_support_filament_id]/2.4053*60}
{else}
    ; --- RIGHT NOZZLE: Default behavior ---
    G1 E5 F{filament_max_volumetric_speed[initial_no_support_filament_id]/2.4053*60}
    G1 X290 E10 F{filament_max_volumetric_speed[initial_no_support_filament_id]/2.4053*60}
{endif}

Might be worth a shot to solve the issue with gapping when starting a print with the left nozzle.