So after a long print the walls in the print begin to weaken and it appears they might not be printed at all. In the upside down picture you can see the weakness where the two pieces are separated. I'm wondering if perhaps reducing my speed and changing the extrusion size from .35 to .45 which is larger than the extruder itself. Thanks for any help and suggestions!

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  • $\begingroup$ Is this a one-time problem or do you see it regularly at about that height? $\endgroup$ – Carl Witthoft Jul 11 '19 at 15:16

What you refer to as weak walls in fact are under-extruded walls. This can be caused by multiple sources, but, since the print recovers this most probably is caused by filament that is entangled on the spool (this causes more friction for the extruder and as such less flow, so under-extrusion; like as if the filament is being pulled back). Any other source that may induce extra friction is equally valid. E.g. kink in filament when using a Bowden configuration (long time extra friction in tube) or friction on the spool itself (I once had severe under-extrusion as the spindle of the spool caught a plastic bag which got wrapped around).

  • $\begingroup$ It could also be caused by a kink in the filament (more friction on delivery) or a section of undersized filament (proper advancement, but lower volume). $\endgroup$ – Davo Jul 11 '19 at 13:40
  • $\begingroup$ Besides a kink (which is very possible) I dropped a roll once and tried to re-coil it back up. In doing so I ended up accidentally looping the filament under itself. Exact same result of additional friction, but something to keep in mind if you're as clumsy as I occasionally am. $\endgroup$ – Diesel Jul 11 '19 at 22:02
  • $\begingroup$ @Diesel Looping filament under itself is considered entanglement in my opinion. I think we all have had the experience where you forget to secure the end of the filament causing the filament to unwind. :-) E.g. I use a spool of 2.85 mm POM filament, if you let it go (I let it slip once...) virtually the whole spool unwinds considering the high stiffness of the POM in combination with the large diameter. $\endgroup$ – 0scar Jul 12 '19 at 8:35
  • $\begingroup$ @0scar, I'd completely agree with you on that. But, unless you've done it before and identified the problem, you might not necessarily think of it. I just thought it might not hurt to point it out for anyone who hadn't thought of it as it drove me NUTS for a week of printing before I put two and two together and fixed it. $\endgroup$ – Diesel Jul 14 '19 at 21:26

A filament tangle is one possibility, one alternative is that you are seeing a jam in the extruder. The trigger for a jam might be excessive retraction, heat soak or some other issue with the heat-break. Less likely, you might have an electrical problem which is position dependant.

The extrusion-related issues won't necessarily react in an 'obvious' way to any tweaks you make to the parameters (for example, slower might exacerbate heat-soak because the downward filament flow and thus cooling effect is lower).


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