LulzBot TAZ Tool Head v2 skips filament


Recently I upgraded my Taz4 to the new Toolhead v2.
With my timelapse camera I discovered some strange behavior for the first and sometimes second layer.
I uploaded a video to youtube:

On the right upper corner you see the filament spool turning. But suddenly it stops turning but the print head is still printing. So no filament is now printed just air. But then after a few moments the tool head started to feed again the filament.
What might cause this? Do you have an idea?

PS: Filament is normal PLA


Check the extrude idler tension and the small gear setscrew. Also ensure that the bed isn’t too high on that side. You may also have a motor cable short at full extension or retraction on x? But usually that is persistent. The video makes it almost impossible to see what is going on. A real time first layer clip with much higher resolution would be much more useful.

thx for the help.
I think that the tension on the idler tension is already quite firm…
Or is maybe the bed too warm (60°C) and then the whole head gets to hot and the filament to flexible etc…

The short can’t be the problem since the motor was still turning but somehow didn’t push the filament through the nozzle…
And also the temperature was always at 205°C.


If the problem is reproducible, try aiming a small fan at the printer during the print to see if that corrects the problem. I have had an issue with the hotend fan on a couple printers where they are spinning but not at 100% so, on longer prints or prints with a lot of retraction, heat creep related filament swell will cause some sticking in the cold section of the hot end. That sticking results in intermittent stoppages and print failures.

It might be a intermittent open on the motor wires is causing the motor to stop feeding on the right side of the bed.

Currently it is not reproducible however I will try this with the fan. I will switch the main Fan already on for the first layer and not just for the 2nd and higher.


You are printing with PLA and I notice that you have the little blower cooling the heat sink on the hotend.
You are running into what is called “heat creep” in the PLA filament. Basically, the filament is softening too early in the extruder.

The new Taz 6 has gone away from the tiny blower and uses a big 40 mm muffin fan with a duct on the heat sink. (I think that is a bit overkill, but it does cure the problem.) Before they came out with that, I designed a duct and a 25mm fan for the heat sink similar to the ED3 design which pretty much cures the “heat creep” problem that you are having.

Here is a link to my duct design:

Bill D.

The filament cooling fan you can control won’t have any effect if you have a heat creep problem. It is the small squirrel cage fan that can become weak and cause heat creep.

I have the v2 Toolhead this has the fan you describe or is it just too weak?


Sooo it just happend again… The print was 1/4 finished and suddenly it stopped feeding filament…
This time at a different position so it can’t be the motor wire.