Constant extrusion failures

The initial month or two, the prints have been fantastic with no extra effort to get them working. However, over the last week I haven’t been able to get a successful print. This print failure seems to be because the primary extruder fails to feed.

I observed this during one of the early layers on a really long print where the extruded nGen filament began to “sputter” instead of printing a solid line. So while it was still printing I released the filament from the extruder and pulled out the filament. A portion of the filament appeared to be carved out. After trimming the damage portion, I re-inserted it into the extruder assembly and it was printing fine. This morning it looks like a similar problem had happened.

I’m printing nGen with the standard settings with the nozzle at 230C bed at 85C which has always worked before.

Under the Cool heading in the Advanced settings the fan is configured as the following:
Fan full on height 6mm
Fan speed min 40%
Fan speed max 60%
Min speed 10 mm/s

Since it’s colder outside, should I be running the filament at 5C or 10C hotter than normal?

System: Taz 6
Extruder: Dual v2.1

Something that helps me in 3D printing and in all problem solving generally is to ask “WHY?” 5 times

I had a similar issue start happening recently and here is how it went for me:

Filament is grinding out. WHY?
Filament is not being pressed against the hobbed bolt hard enough. WHY?
Idler roller mounting feels wobbly but adjustment screws are in usual location. WHY?
Idler Roller Bracket has a crack in it by the bolt thus relieving pressure on the hobbed bolt.

Of course there may be dead ends but at each step just think of other causes for the step above. and always check obvious things first–don’t get exotic…the proverbial “is it plugged in” is a good one for electronics…

Of course there are other potential things like binding of filament that causes the hobbed bolt/motor to work too hard, appearance of purging the nozzle–is heat/heater/thermistor working all the time? etc.


Switching to the single extruder that came with the instrument causes the printer to work as intended, so there must be something odd going on with the extruder assembly.

I cleaned it out as much as I could without dismantling it. Maybe I need to take it all the way apart and clean it out. However, I can reload the filament and use the console to extrude filament just fine.

Is there a detailed assembly guide for the dual extruder that I’m missing?

After switching back to the cleaned dual extruder, same issue occurs. After a couple good layers the nGen extruder seems to lock up.

Could potentially be the nGen material hardening in the extruder assembly while the PVA is printing. Is there a way around this? Run the fans slower, nGen extruder hotter?

I don’t have much experience with nGen. In general, a few degrees hotter should be fine as long as you’re within the manufacturer’s recommended temp range. A few turns of the idler screws to tighten further can help also… 8mm seems to be the optimal spacing, jigs are available on thingiverse.

Just to update, I think I found the culprit.

After cleaning the dual extruder thoroughly, and testing the temperature settings with the single extruder successfully, I switched back to the dual and tried it again.

Unfortunately, now the primary extruder on the dual is completely fused and will require replacing the hot-end.

What seems to have happened is that the mounting point for the hot-end cooling fan was under-designed and was no longer cooling that portion of the hot-end properly. Which in turn caused the extruder to fail. The cooling setup on the single looks like a substantially better design than the dual. At the very least, this connection between the fan and the extruder assembly should be metal and not printed. The fan should also have been supported better so that the alignment of the fan isn’t completely reliant on how tight that screw is.

Yeah… the heatsink fan mounts on the dual extruder v2 are fragile and leave much to desire. I’ve broken one mount as well… can’t remember what I did to reinforce, but its holding. To LB’s defense, there’s not much room in there and the blowers only have one screw for mounting.

I primarily print ABS, so I’ve never had the heat creep issue. There is a modification to replace the blowers with 20mm box fans… I’ll look for the thread…

EDIT: Here’s the mod thread: