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For some reason on my Raise 3D N2 plus with a Bondtech-Extruder I am sometimes seeing filament jams and sometimes it prints without any issues. I am using PLA at 215 °C.

When the filament is jammed I have to pull it out, remove the tip, and then I can load again and everything works perfectly fine again. I have attached a picture of what I pull out of the extruder each time. It looks like the bottom part is some kind of skin of the filament.

It's hard to see but the tip of the filament is a little thicker, so it's possible that this can't be pushed into the extruder, but why would it build up there? I am using 3 mm retract, could that be the issue? Or is my extruder not hot enough?

Filament pulled out of the extruder

Thicker part of the filament

Greenonline
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DerDrucker
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1 Answers1

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  1. Heat creep can cause the filament to jam. The thicker end on a Bowden tube extruder matches heat creep. However, since lowering the extrusion temperature didn't help, it does not look like heat creep.

  2. Retracting too far can cause the filament to jam trying to go forward again. Have you tried less retraction?

  3. PETG can jam if you print too fast. I'm unaware of this problem with PLA. However, this problem gets worse with lower extrusion temperature.

  4. What is missing in the images for a direct drive extruder is any sign of the drive gear engaging the filament. There are no teeth marks where the gear pushes the filament and no notch in the filament where the gear turns but doesn't move the filament. Is your filament drive gear too loose against the filament to keep pushing it through the nozzle?

Perry Webb
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  • I tried less retracting, (1mm now) aswell as a lower temperature and while the part that caused jamming before printed successfully and now on the next part I started having issues on the second layer, the behavior is exactly the same as before and the pulled out filament looks exactly the same as before (also same length). It seems to be stuck right unter the heatsink in the metal throat tube (that's this one https://www.raise3d.com/products/throat-tube-v2-n-series-printer-only/), that's where the thin, non-theaded area is. The 1mm retraction shouldn't cause a jam there, right? – DerDrucker Jun 16 '21 at 15:50
  • 1 mm retraction shouldn't be a problem. The problem is when you retract the filament past a seam, then it catches on the seam going forward. Does the filament buckle anywhere? – Perry Webb Jun 16 '21 at 16:52
  • Not entirely sure if I understand what you mean with your question. I can't see the filament after the extruder motor, so no idea what happens there. When I pull it out I can see that at the tip the filament is thicker. Obviously that is the problem (or at least part of the problem), but I can't figure out what causes it. Even at low temperatures it doesn't work any better. Is 80mm/s print speed maybe too fast? – DerDrucker Jun 16 '21 at 17:06
  • It appears you aren't seeing bent filament when you remove it, such as the pictures at https://3dprinting.stackexchange.com/questions/15629/what-are-ways-to-avoid-heat-creep – Perry Webb Jun 16 '21 at 18:34
  • PLA should work at 80mm/s. That would be too fast for PESTG, which likes 50mm/s or less. – Perry Webb Jun 16 '21 at 18:37
  • My filament does not look like that, it's perfectly straight and even that thicker tip is straight, it's just too think to go through that throat tube. I think the throat tube might be damaged, I'll remove it tomorrow and check as on the tube that I have on my desk it can be pushed through. Maybe it is bent or something is stuck in there or whatever..... – DerDrucker Jun 16 '21 at 20:59
  • This wouldn't let me rest ;) So i disassembled the throat tube and checked it: All fine, no damages and nothing is stuck. I also added more detailed pictures of the thicker tips, and as you can see it's basically always the same that's happening. – DerDrucker Jun 16 '21 at 22:23
  • Another possibility is defective filament. Does the filament have thick spots on it? – Perry Webb Jun 16 '21 at 22:26
  • I looked at the filament, took about 10m from the spool, put it on the floor and then carefully looked at it and used a caliper and pulled the filament through it. I didn't see anything unusual and the caliper didn't get stuck. Then I double-checked with one of the pieces that I pulled out of the extruder, tried to pull it through the caliper and it got stuck. So now I know, that the next 10m of Filament are not too thick. My print only needs 2m of Filament, so this should mean at least 5 trouble-free prints if the filament is to blame. – DerDrucker Jun 16 '21 at 22:55
  • Also what surprises me: When I pull out the filament, apparently I only pull out the upper part and the lower part stays in there. I think retraction might be to blame here (I inspected the G-Code and it printed fine the first layers without retract), let me try a print with retraction completely disabled. When that succeeds I might have to ask questions about oozing, but I'll think about that when I get that far ;) – DerDrucker Jun 16 '21 at 23:00
  • It looks so much like heat creep in a Bowden tube. Is there any chance the hotend is staying too long at extrusion temperature without moving? – Perry Webb Jun 16 '21 at 23:20
  • No, the hotend is constantly moving and extruding during the print. Also my extruder is direct drive and not a bowden extruder. Since I discovered the retracts in this G-Code I am pretty sure it's retract related. That would also explain why it seems to happen pretty consistently at the same point on the same model but slicing it with different options has different effects. So far the new print runs nicely, I'll check in the morning to see how it came out (printing at 205 °C now, retractions disabled). – DerDrucker Jun 17 '21 at 00:24
  • See 4. added to answer – Perry Webb Jun 17 '21 at 11:19
  • There are marks on the filament and where the gear is grinding the filament is where I break it off to load the new filament in. This no-retract print succeed, but with some oozing/strings that shouldn't be there. I'm not really sure what to do now, either retract and risk messing up the print, or don't retract and have strings all over the print. I think setting the retraction distance below 1mm doesn't really make sense? – DerDrucker Jun 17 '21 at 13:55
  • Lowering the extrusion temperature reduces the oozing. However, lowering it too low reduces layer adhesion. – Perry Webb Jun 17 '21 at 14:27
  • If you need a higher extrusion temperature to stick to the bed, you can use a different temperature for the first layer. – Perry Webb Jun 17 '21 at 14:29
  • Just had a jam again on a part that I printed 2 times successfully before that. I didn't even re-slice it. Maybe heat-creep is indeed the issue and the printer had enough time to cool down? I'm surprised there aren't more reports about this then, and there are fans cooling the heatsink, the temperature there should be sufficiently cool – DerDrucker Jun 17 '21 at 21:53