Extruder/hotend stuck with glow filaments - possible workaround

Some filaments, especially the glow ones though are a total pain to use.
You start a big print and all seems to work fine, you go to bed and the next morning you find a failed print.
Not only did the printer fail to realise there is nothing coming out of the nozzle - often the extruder is blocked.
Easy fix - IF the thing would be designed user friendly.
With the filament stuck you take those drive wheels out, can’t remove the filament without getting creative.

If it is not the extruder that ends with a thickened piece of filament then after a filament change or completed print the glow filament more or fuses to the heatsink.
No teflon liner means we have a problem.
You can fix the lot in under 30 minutes with the right tools but it does not fix the issue causing it.

I wasted quite a bit of time and filament in order to work out what it is exactly that causes the extruder blocks.
Heat creep of course but who would have though the filament softens all the way to the extruder ?
Well, it does at times…
Unless you want to spend a small fortune on a much better hotend this little workaround might be worth trying:

Heat creep is one thing, smashing the filament another.
But that’s what Bambu does by default…

Try this for glow PLA:
Copy the speed acceleration and percentage setting from the 0.12mm high quality profile into your standard 0.2mm profile.
Find the best print temperature!
Somewhere on the lower end between just enough layer adhesion and stringing starting.
Last but not least go into the override setting for the filament and reduce the retraction speed to 18 or lower.
Do a test print to check how low you can go here without getting too many quality issues.
With this you have WORKING start where you play with the speeds in order to reduce the print time.
The retraction is what causes the extruder to block and ongoing slow extrusions allow for the heat creep to creep up.
Prefer an overall lower print speed over trying to go fast and having to slow down for overhangs and fine details - it cooks the filament and the heat creeps up fast.

Keep the filament properties in mind when selecting models for it…
Glow in the dark can be fun but it is not an easy to deal with filament.
Those beads inside hold a lot of heat and that for a long time.
A good flow rate and optimised retractions can avoid almost all extruder blocks…
Just make sure to keep the nozzle temp as low as possible - hence the slower speeds to start the tuning with.

1 Like

The hotend and heatsink are a different story…
On my old printer I had it easy here…
Heat up the nozzle to 260 or so, stick a wire through the nozzle and keep poking.
Then push the filament until the goo and gunk is out.
No such luck with Bambu as you can’t feed directly into the hotend and can’t free the extruder for manual feeding either.
Means we have to try to AVOID that the filament gets stuck here.
Unless your temp is way too low those beads should never be able to accumulate enough to cause a block.
But how exactly does the filament unloading work? :wink:

Right…
First push out a bit of filament - at the highest possible temp of course.
Then cut right on top of the the heatsink and pull the filament back…
Too bad if the filament was still too hot and expanded in the heatsink…
It WOULD pull out there easy if it would not goo all the way to the nozzle…
And while the glow filament goes soft when you don’t want it to - it usually won’t cooperate, not even if you crank the temp to 300 degrees and see smoke coming from the nozzle…
Only way out is going back…
Heat the wire, push it in, heat the hotened and keep pulling until it eventually pops out…

Whenever glow filament is used it is good the flush it out after a print rather than just cutting the filament and leaving the rest in the hotend.
No need for excessive flushing, you only need to clear the glow filament from the heatsink part.

Sure you can. Just disconnect the PTFE tube on top of the hot end and feed it there. You can use the console to step filament through. It’s a good idea to check the tube at that location anyway. It can get chewed up from all the pushing and pulling through normal use. It’s THE hot spot for failure to feed errors.

It’s also about the only way you can do a cold pull and/or clean out TPU.

1 Like

You SHOULD be able to do as you say…
But did you ever try to get this tube off when you also have the filament stuck inside the extruder ?
Most filaments you can hard enough from the AMS to give you just enough filament to get the tube out and to cut the filament, or break it off.
Glow filament does push very well…
No filament loaded, no problem to heat the nozzle in order to try to push filament through by hand …

I am already looking at a double push connector to put in the line going into the printer.
This way I can just screw one out to get the required wiggle room.
Don’t know why but I just dislike using brute force on printers…