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Badly stuck filament

Posted by feistylemur 
Badly stuck filament
October 21, 2016 04:41PM
Well I almost had my new printer ready to try a first print, but I have a problem I haven't encountered before.

I successfully had done a test extrude the day before. So today I was going to double check the steps per mm on the extruder before starting, so I heated up to 190 which previously extruded, retracted and it starts skipping.

So I've tried everything and I cannot get the filament to budge. The nozzle isn't clogged, the filament is sitting about 2mm up in the heat break. I had the nozzle off and checked. I can't budge it even at 250 degrees, I can't even remove the bowden tube with the opposite end removed from the extruder motor. Can't move it by hand. I have no idea what to do next.

This is an e3d v6 with a bowden setup. The filament jammed in it is black PLA which was extruding at 190 in a test extrude yesterday.
Re: Badly stuck filament
October 21, 2016 06:26PM
When you retracted you probably pulled the soft, hot filament up into the throat of the hot-end where it got stuck. You have to limit retraction length and will have to experiment to find what works. Disconnect the cooling fan and heat the block up. The heat will creep up the heatbreak and you'll be able to get the filament moving again.

Or take it apart and run a drill bit inside it to clean out the filament.

If your extruder has chewed a divot into the filament it will be unable to grip and push the filament. A divot in the filament indicates that the pinch roller is not pushing the filament hard enough against the drive gear. Your motor should stall before it ever chews up the filament. Increase the pinch roller pressure using the adjusting screw(s).

Son of MegaMax 3D printer: [www.instructables.com]
Re: Badly stuck filament
October 21, 2016 09:50PM
I managed to get it apart and separate the heat break from the cold end after managing to break the filament off right at the edge of the heat break. I heated it with the stove burner and punched out the filament clog with an allen key.

I did retract it about 2mm before shutting down. But I'm just thinking about it and I also think I may have shut down main power with the hot end still hot. Is it possible that allowed heat to spread with the fan off and melt and clog it?
Re: Badly stuck filament
October 22, 2016 07:16AM
Is the hot-end cooling fan connected to the power supply, or wired in parallel with the heater? It should go to the power supply and continue running even when you reach the end of a print and turn off the heater. I don't know if there's enough heat in the block to cause enough heat creep to jam filament if you just kill the power. In my printer (E3D v6 hot end and bulldog XL extruder) I can kill power and never have it jam, but my extruder has 5:1 gearing and can push VERY hard. It's possible that if your extruder can't provide a lot of downward force the filament could get jammed simply by killing power while the hot end is hot.

Son of MegaMax 3D printer: [www.instructables.com]
Re: Badly stuck filament
October 22, 2016 08:00AM
It's wired to always on and using the stock e3d fan. I may have flipped the power off without letting it cool down though after testing it.

The extruder is geared and quite strong. In any case it hasn't happened to me again. I've printed a few test objects now and initial testing seems to be going ok.
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