I fixed my clogged nozzle!


When I get some time, I’ll try to cull a few posts from here and put together a PDF with some pictures.

Maybe I can submit it to the FLUX Team for review, would rather it come from them, or at least have them look it over too.


From time to time, I replaced the nozzle since filament won’t pass for some reason (unknown). But lately I got a raft that came loose from the print bed and stuck to the nozzle - which in return didn’t stop oozing out PLA.

Now I can gladly tune in here since I also experienced a clogged nozzle 8-O … the picture does not show the whole mess - most of the PLA chunk is inside the extruder housing, where it neatly engulfed the heater and its cabling. Sigh.

Finally, the rods came loose and presented what had happened overnight:



Took me hours to dismantle the extruder and carefully cut the mess to tiny pieces …


@pfeerick, go ahead and issue him the merit badge, that’s a pretty good one :laughing:


@BoozeKashi I wish I could :wink: That indeed was a good example of what goes wrong when the print detaches and follows the head around… Maybe someone needs to come up with a ‘Oh c$#p, the print’s attached to me’ detector for 3D printer print heads! (As well as a “wtf? where’s the print gone?” one for when the printer shoves it randomly off the print bed!) :laughing:

I have seen a photo from the forum for my other printer where it was located on top of of a filing cabinet, and PLA plastic is all over the front of the cabinet and on the floor, as the print shot off the front of the bed… and the printer just kept on goin’ … :laughing:


Hmm, those aren’t half-bad ideas actually. Perhaps with some creative use of optical sensors that could be done.

The print getting knocked off the bed would be easier, just set up optical gateways (like the “bing-bong” pass through detectors in convenience stores) around the sides of the bed. After a print starts, if anything trips that, PAUSE!

The print attached to the head would be a little trickier to do since there are so many ways a piece of gum can get stuck to something :slight_smile: I wonder though, that’s got to somehow change the resistance or heating capacity of the nozzle somewhat. I’m just not sure if there’s enough capability in firmware to measure that. I know Marlin firmware is getting really good at detecting thermal runaway, but that’s a much more pronounced effect. A slowly building wad of filament is much more subtle.

Interesting ideas though. Would’t mind hearing thoughts from some Jim’s on this. @proclaim @Jimustanguitar


lol… indeed optics would do that nicely. Could perhaps do the ‘PLA attached to the print head’ via optics as well with a slight-resign to the head… addition of optic beams that are blocked by the filament if it builds up.


I’ve wondered about an “endstop ring” or some sort of mechanical switch down around the nozzle before. I think I’t’d be difficult to detect a thermal difference without causing a lot of false positives, but I’m not sure.

What about looking for unusual triggers with the FSRs and hotend accelerometer? The print head knocking a part off the bed seems like it would cause an ‘event’ recognizable by the sensors on both devices.


I don’t know if the FSRs are sensitive enough to actually detect the weight of average prints.

I was actually thinking more for all printers in general, not just FLUX specific, which is why I was thinking just a setting up a simple optical gate type setup on any open side of the printer. Could be done with fairly small bubble housings to hold the sensors, any trigger would trip a simple gcode dwell command. A few different ways to skin that cat.

The print stuck to the head, you are right, that’s why I tagged you in, the thermal detection I think would be too difficult, there just isn’t enough sensor information to detect it that way. An end stop ring type switch, I think I get what you are saying, and that might actually work. Offset it 4mm or so from the nozzle, so about an 8mm ring on a pivot switch. Enough leeway that it shouldn’t accidentally trigger, but close enough to shut things down before it wads up a hot-end too badly… Nice!

BTW, this counts as prior mention, so Open Source :wink:


Disgustingly I now get clogged nozzles pretty often, with PLA agglutinated to the outside of it only one of several issues.

Note that in some cases the nozzle wasn’t tight enough so PLA oozed out through the thread (another issue).
I always put a copper washer under the nozzle now and take care to clean the adjacent surfaces.

For reasons I don’t know yet every once in a while extrusion becomes far too sparse, which ruins hours of printing and makes disassembling at least the nozzle, if not the entire toolhead a recurring necessity. When this happens, the print did not go well beforehand - it is quite brittle because of insufficient cohesion of layers (even with the print temperature already increased to 210-215°C):

A closer look also reveals that there are several brownish “mice poo” clumps woven into the part, mainly the support where the toolhead travels fast. Apparently, degraded PLA that was stuck inside the toolhead for quite a while … what else could it be eventually?

Some time ago a “Commands/Set Toolhead Temperature” function was invented in FLUX Studio which comes pretty handy when taking apart the print head without much torque applied on the nozzle against hardened PLA residue.

But last time I did this the temperature ran away for reasons I don’t know either … first I noticed a strange smell from the toolhead, then fume rising from its underside - emergency! Time to pull the DC plug immediately. Has the sensor gone wrong eventually? How do I find out? Are there spares available? Second source? Or did beta Software trick me?

Anyway, I now got second grade burns on the toolhead plastic…


I don’t know what the reason for the thermal runaway was… entering a value into the “set temperature” field didn’t always work, but doing it via the up/down buttons with the mouse then did. Maybe some non-initialized value … 999°C or the likes.
Yep, my fault, since I used the beta version of FLUX Studio.

But I guess I found what caused the frequent nozzle clogging: The PTFE tube inside the extruder heat sink was extremely worn, when I pushed out the filament residue with a cut bicycle spoke it popped out with it:

Obviously the filament got more or less stuck within the PTFE tube - even the new (updated) version of the filament transport mechanism couldn’t cope with the additional friction. Sometimes a bit of the smolder got through the nozzle, causing the brownish tags and “mice poo” in my print.


Almost identical pics on the FB group of what happened to mine. The internal PTFE tube finally ‘cooked’.

I would skip that copper washer though, the way the hotend is designed, the heatbreak threads about halfway into the block and the nozzle should meet it flush. If you are putting a copper washer in there, you are introducing a gap between the two, which can create a gap or pocket inside the melt area.

To prevent some of the thread leakage, you can wrap plumbers PTFE tape or even better, use thermal paste on the nozzle when you install it.


Lately I get clogged nozzles and stuck filament quite often, ruining most prints, especially the larger ones.
Even after I changed the little PTFE hose things went bad.

Now I found a clue that besides the nozzle, other parts through which the filament runs become far too hot:

As one can clearly see, the plastic got deformed early at the entrance into the print head!
That of course was too much for the little filament grinder above … once again, stuck.

Btw., how many of the fans in the print head are supposed to be running? All of them, I guess… but only one is. Or are the fans blowing air to the nozzle only driven when needed? A fan failure would eventually explain overheating.

The Trophy Room: Show us your best prints!

I’m not sure… but I suspect it’s one running continuously once the head warms up, and then the other two start up after the first few layers. If not, then its 2 continuous, 1 after first layers? :wink:


Yep, you’re right: The fans start only a few layers above the platform. After I took the print head apart (again), no sign of overheating any more - but I found that the filament part below the deformation (see picture of pulled filament residue above) hardly fits into the PTFE hose… why it softened right there in the first place is beyond me.

Still, I’m getting a brittle print structure (filament transport mechanism clicking, print becomes transparent and fragile and does not properly stick) after a few centimeters of printing! Replacing the nozzle immediately fixes that, so if I notice the clicking early enough I may save the print through frequent nozzle changes. Or even pausing to cool down the print head.

One can clearly see where I replaced the nozzle during print.

All this did not happen when my Flux Delta printer was new … I’m suprised to see that it has worked some 800 hours already. This morning it got clogged nozzle no. 16. So far, I narrowed the problem down to the filament getting softened and stuck within the PTFE tube above the nozzle, which must not happen if this part is properly cooled.


After the last meltdown accident I massively cut free the hot end of the print head from its surrounding plastic … then reassembled, omitting the top cover. Switched back to the original Flux filament instead of esun3d and - fingers crossed - things get better!

I even managed to print a fine metric thread :slight_smile: … perfect fit with a brass nut:


One fan (with red/black wires) runs continuously, that is the fan that cools the hotend to control the melt zone.

The other two turn off and on as controlled by software, they are centrifugal (aka squirrel cage) fans attached to the little vent pipes. They are the part cooling fans. Those are the ones you can control in software like S3D by layer and fan speed %.

Just remember there should be one (on the front right if your print head is installed correctly) that should be always on as long as the print head is hot. If you ever notice it is not, then something very, very bad is about to happen.


By the way @edefault just by looking at your pics, you are likely going to need to replace the PTFE tube inside that toolhead soon. It gets cooked and that leads to frequent clogs/jams.


Yes, I know … I got some very good prints lately with a new PTFE tube (and a new nozzle of course), but only a few days of 24 hour printing later the filament refused to unload - stuck again:

It was a bit tricky to get the threaded (steel) part loose from the circular-finned heat sink. Luckily some standard filament tube from eBay also fits.

With the print head finally reassembled, fumes rose from beneath a transistor on the PCB 8-O … maybe I finally and irrevocably toasted the print head electronics of my precious Flux Delta.

Print heads are on the Flux’ web shop site, but - sold out for a long time.


I’ve been having lots of trouble with my extruder clicking lately. It looks like the PTFE tube inside the heat break is clogged. Is the best solution to replace the entire heat break or to just dig out the PTFE & replace it?

Anyone have a good source for a heat brake that fits?

What about replacement nozzles? What’s the current favorite? (Micro Swiss MK8 0.4mm wear resistant nozzle & the Amazon multi-pack are listed above.)


EDIT: I ordered a couple new nozzles and a piece of Teflon tube from the FLUX store. My filament sensor’s bad too, so I ordered one of those. I’m still curious about replacement heat breaks though.


That thermal paste / PTFE tape tip sounds good! Could you explain better? I’m having some leaks from nozzle thread, and maybe from another source too. Did you apply the paste before inserting the nozzle, on the screw? Does it protect the possible spaces, avoiding PLA leakages? I thought thermal paste would keep itself semi soft, and woudn’t be able to hold down the plastic.
I’ll try out a plumbers PTFE tape first, hope it works!