slinky mode

Well, if you found the jam inside the bowden tube, there’s no reason to keep second-guessing, it’s jammed.

If it always happen at the same point, I’d look at what the printer does differently there. For example, I know that if I set the cooling fan on my printer to more than 10%, it almost immediately jams (due to a design problem). But since it’s all the way into the tube, I’d suspect some absurdly large retraction.

Or, maybe, look for another heat source near the failure point. It doesn’t take a lot to bulge PLA, any electronics touching it may be enough.

(But just to add, yeah, jamming either looks like that or the extruder eats up the filament and loses contact. The better designed your extruder is, the more likely that it will look like that.)

That is a very odd failure so not 100% sure. If I had to take a punt I would say the nozzle jammed from the mentioned heat creap issue, eventually the silk pla broke in the extruder as it’s very brittle, combined with retractions. It then was then able to work its way out and make some noodles for you to enjoy.

What retraction settings do you use?

I have seen something similar to this while printing tpu but never with pla

I have heard of silk pla filament jamming but this looks like more of a retraction problem to me

If it’s a jam check to make sure that your nozzle is clear of any debris

If it’s retraction

Either too many retractions happening too quickly breaking the fillament at your extruder

Or

Retraction distance is too far

A lot of that slinky filament looks grounded or marked by the extruder gear. If it only happens on longer prints, ambient temperature might simply rise too much over time. Even the best extruder cooling fan can’t help much if the ambient air is too hot.

I need to vent my enclosure when doing super long prints or when printing hotter stuff like PETG.

That looks like Capricorn tubing. It’s got a 1.8mm, not 2mm, inner diameter.

I used to regularly run into cheap filament that varied up close to 1.8mm in diameter that would get jammed in the tubing.

When I did, tossing the roll was my only option.

Capricorn is great for reducing filament backlash and printing flex, but requires very consistent filament.

Thanks for all the comments and suggestions! I’ve cleaned the whole thing up and I changed the PrusaSlicer retraction length from 6mm to 2mm. Let’s see if this changes the result.

This printer is mostly stock Ender 5 Plus. I upgraded to an all metal extruder (original one broke) and capricorn bowden tube a while back. Usually the defaults have been OK and I print often.

My extruder gear leaves quite a track mark on the side of this filament and I wonder if this is contributing. I’m in a very hot and humid region and this spool is about a year old. I did have it in my filament dryer for about half a day right before this print, so it was more malleable than usual.

Oh, and this print is a print-in-place retractable cosplay katana, so there is a ton of intricate details which seems to result in a lot more retractions and tiny movements than usual.

Without more information it is hard to say. What hotend do you have? What fan (manufacturer, model number) is cooling the hotend? Did this happen to you before or was it printing fine? Did you change anything?