Early issues with new K2 Plus Combo - CFS condition and filament jams

[Zap_05]

Hi all,

I’ve just received my new K2 Plus Combo in the last 2 days and wanted to post about some issues I’m seeing — hoping to get some input.

First up — the CFS unit:
The CFS that shipped with my printer looks like it may have been used. It has visible scuff marks on the outer case, and there’s filament dust or ground-up filament visible inside the clear plastic section underneath where the PTFE tube exits.

I assume these units undergo testing, but this one looks like it might have chewed some filament at some point.

Fortunately, I had ordered 2 CFS units — the one that shipped separately looks brand new (no marks or dust), so I’ve connected that one to the printer for now.

Print results so far:

• My first print (2 hours) went off without a hitch.
• Second print had adhesion issues — that was on me (model had a very small footprint).
• Third print jammed at 3% due to a clogged extruder. I opened it up to find the filament bulged between the extruder gears.

I cleared the jam and restarted. It jammed again at 49%. Cleared it again and managed to finish the print.

Extruder question:
I noticed that my extruder doesn’t seem to have a tension adjustment screw. There is a threaded insert where I believe one should be. Is this normal on the K2 Plus Combo extruder?

Summary:
I’m a bit disappointed to be having 2 jams this early with a brand-new machine. I’ve been a long-time Creality owner (Ender 3 Pro, Pro V2, Ender 3 SE and KE) — my KE is an absolute workhorse with no issues (touch wood! ).

So — a couple of questions:

1. Is there meant to be a tensioner bolt on this extruder?
2. Does it sound like my CFS unit might be used / refurbished?
3. Is there a reliable fix for filament bulging out between the extruder gears? From what I’ve researched, the likely cause is heat creep up the nozzle — is this accurate?

Would appreciate any advice — thanks in advance!

[Lu_Zhang]

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[rdtsc]

@Zap_05

Is there a reliable fix for filament bulging out between the extruder gears? From what I’ve researched, the likely cause is heat creep up the nozzle — is this accurate?

Possibly. Others have noticed that the extruder motor is always at 100% power (never idles) so gets hot. After a few prints it is hot enough to conduct that heat into the filament through the pinch roller(s). Chance is greater with chamber heating. One user plumbed an air line to the extruder motor and says that forced-air cooling helps. I noticed that if the “Motors Off” button is pressed, this also powers off the extruder motor, allowing it to cool. We now always press “Motors Off” after every print, and (knock on wood) have not seen this since.

[JBechthold]

I Had the same extruder jamming issue using PETG, with the bed temp at 70c and filament at 240c you get heat creep and if your filament is not VERY dry you will clog your nozzle and that will cause the filament to get jammed on the extruder. Keep your model fan and case fans at 100% after the first layer to help dissipate some heat, I also tried leaving the top glass about 1 inch open, not very convenient as my CFS is on the top of the K2, but it appears that and the fans have solved the extruder gear jamming issue, at least for now

[Zap_05]

What do we think about the chances I got a refurbished unit? I’ve attached some photos down below.