My printer stops extruding randomly, what am I missing?

[infiniteloop]

@re_tour

So whatever happens, it happens below the ptfe tube.
I already changed the nozzle and saw no sign of residual pla

Between these two parts, the heat break should do its miraculous work. But, as you state:

I can only guess there’s clogging...

Exactly. Usually, a hotend simply works. If it doesn’t, we can only hypothesise what goes wrong. Some time ago, I spent weeks figuring out that the chemistry of a certain PETG filament slowly built up unflamable debris in the hotend - I couldn’t even torch it (and believe me: I had enough petrol and cigarette lighters at hand). So: strange things happen.

That’s not to say your case is similar. You just encounter a similar mess. So, hopefully, you can resolve the issue with an exchange of the hotend. Anyway, the ultimate way is follow one hypothesis after the next, to take one step at a time. At the end, we know better.

[deckingman]

@infiniteloop said in My printer stops extruding randomly, what am I missing?:

............... Some time ago, I spent weeks figuring out that the chemistry of a certain PETG filament slowly built up unflamable debris in the hotend - I couldn’t even torch it (and believe me: I had enough petrol and cigarette lighters at hand). So: strange things happen..........

Someone much more knowledgeable than me about chemistry, once told me that if you over heat PET-G, it will "carbonise" and that the only way remove said carbonised filament is by drilling it out (or use explosives) . So perhaps lowering the temperature of your problematic filament might prevent a recurrence.

[infiniteloop]

@deckingman

So perhaps lowering the temperature of your problematic filament might prevent a recurrence.

Thx for the explanation: that's gold standard, deckingman style - appreciate it. Well, I tended to apply explosives: new nozzles and tubing, the filament is on my eternal blacklist.

[oliof]

@re_tour said in My printer stops extruding randomly, what am I missing?:

The cooling fan is a noctua 10x10 fan with a step down converter, which I don't think is an issue(but I've been wrong before sooo...)

I would not rely on a Noctua 40x10 for hotend cooling. A 40x20 may work if there is free airflow "behind" the hotend. Its quiet because it has almost no air pressure.

[re_tour]

@oliof That noctua has been there for almost half a year and there were no issues with it.

@infiniteloop So...today I got back to troubleshooting after leaving my printer alone for a few days so that my frustration would go away somewhat. I also picked up the phaetus dragonfly bms hotend today and put it in my printer.

I set it up and everything, bought a new generic ptfe tube (no fancy capricorn stuff) and after I put everything together I started the print...and yet again...the issue was the same...I couldn't believe my eyes...I was in utter disbelief...how, what, why...I have changed everything, there can't be any issues...I even pulled the ptfe tube out and put the filament in directly to check if there was any clogging, but there wasn't. And then...when I clicked on extrude on the duet surface, I heard the extruder stepper moving, but the gear didn't turn...then it hit me: I have upgraded the extruder part with a metal kit, which included a new gear for the extruder, but instead of the factory pressure fitted one I now had one with two miniature screws...which I didn't tighten strong enough, which (sometimes!!) led to the gear slipping...not always, just randomly.

So, turns out that I have been very negligent when putting the printer together the last time, it could've been one mistake or multiple failures at once which caused the print failures.

At long last, I can finally present a fully printed test cube! I really hope that this is where this story ends and that – at least for a while – I can print my creations in peace again.

Thank you @infiniteloop ,@oliof , @Exerqtor ,@jay_s_uk and @deckingman for the help and keeping the spirits up!

[Exerqtor]

@re_tour
Glad to see you finally got it sorted out! It's easy to loose track of where and what might be the issue if more than one mod/rebuild/new part is being introduced without testing between each step, I've done it myself more than once lol.

[infiniteloop]

@re_tour Nice little cube - reminds me a bit of the first iMac… sorry, last century

Sure I’m glad you found the culprit. In my eyes, the most valuable achievement after this tour de force is that you now have profound knowledge of how each and every component of the filament path works - you’ve really touched every single aspect. Congratulations, truly

[re_tour]

@infiniteloop I cheered too soon...

Now that I started printing a part that I made, I started having problems.

It seems like I've got some heat creep going on, however, I can't reproduce the issue manually. I already set like 0,5mm retraction, I have the same result.

I tried pushing the ptfe tube as far as I can down the hotend but it won't go any further...

[infiniteloop]

@re_tour

It seems like I've got some heat creep going on, however, I can't reproduce the issue manually.

A heat creep develops over time, sometimes, it needs an hour to show up. So you’re right: it’s hard to reproduce in tests.

Maybe it’s a good idea to take a break and to summarise your current configuration: I understand that you have a working extruder, a dragonfly hotend and fresh PTFE tubing? Now, what kind of filament did you use, at which speed, which temperature?

Assuming all of this is fine, we are left with a topic @oliof brought up: is the cooling of the hotend sufficient? Can you publish some images so that we get an idea of the air duct and the air flow before and behind the hotend?

[re_tour]

@infiniteloop Yet again, I must say that I did something really stupid, which I just came to realize....

So...the thing is, that to make my life easier during wiring, I put the part cooling fans and the hotend fans on the same step down module...which means that unless I manually turn the part cooling fans on, the hotend fan won't be on until like the second-third layer or so...which I guess is plenty enough time for a clogging to happen, but correct me if I'm wrong.

But anyway, yes. Extruder stepper motor is working, motor gear fixed in place, marked with a sharpie to know if its slipping. Ptfe tube check, hotend is good, coupling is good. I've tried different PLA-s, Gembird, 3D Jake eco PLA and filamentum. Hotend was set to 220°C with the filamentum one and 210 with the gembird and 3DJake.

[infiniteloop]

@re_tour

the hotend fan won't be on until like the second-third layer or so...which I guess is plenty enough time for a clogging to happen …

The hotend fan should be triggered at 45°C - you'll have to add the time until the hotend reaches printing temperature to the time for the two layers. Let's see what happens after you've rewired the fan …

[re_tour]

@infiniteloop I've wired the hotend fan to the board fan, which also turns on at 45°C.

Seems like the biggest failure in this rebuild was me. Never mind, at least now I'm (almost) completely aware of how and why my 3D printer functions and hopefully I can troubleshoot almost anything that happens which is extrusion related. Thanks again!

[infiniteloop]

@re_tour

I've wired the hotend fan to the board fan, which also turns on at 45°C.

That's unwise: The board fan refers to the temperature of the MCU, whereas the tool fan should be coupled to the thermistor on the hotend. The MCU not even tells the truth about the (potentially) hottest components on the board - usually the stepper drivers. However, it can be used as an indicator when active cooling of the board would be desireable.

When the hotend is activated, it's readings go rapidly in excess of 45°C - the MCU stays cool, in other words, the two temperature values are absolutely unrelated. The tool fan must step-in as soon as the hotend becomes hot, else, the cold part of the hotend is heated up, too - which is something you would like to avoid.

If you think it's too much wiring effort to reconfigure your hotend fan, simply set it to "always on".

[oliof]

@infiniteloop some people turn the board fan on based on the hotend temp taking it as a proxy for "machine will get load". So thats not necesarily wrong.

[infiniteloop]

@oliof

some people turn the board fan on based on the hotend temp taking it as a proxy for "machine will get load".

Interesting approach. I could not find hints to this in the config of the OP, but at least for the tool fan, this would be good news

[re_tour]

@infiniteloop I'm back after some rest and I can gladly say that this saga ends here.

I realized that wiring it straight up to the board fan wasn't a great idea, so I configured two separate fans: one of them is the part cooling fan and one of them is the hotend+board fan. The latter turns on when the hotend reaches 30°C, which means both the hotend and the board gets cooling whenever there's job to be done. The part cooling fan works as intended, I just separated it from the hotend fan.

I dare to post these results after 4 test prints, all of which were successful with no issues whatsoever.

I thank all of you, especially @infiniteloop and @oliof. Because of you guys I now have an insight which I didn't before and now can troubleshoot much more stuff on my printer as before. There's always something new under the sun I guess.