[Risolto] Extruder clicking - Extrusion stops mid-print (Heat Creep)  

General sense...

PLA and PETG should not generally need to be printed in any form of enclosure.  Doing so can create the symptoms you describe.

Open that door.

Try to lower the ambient heat around your print - bed temps mainly, especially w/PLA.  That should make the amount of hot air being recirculated through the hot end.

It's a couple of years old - when's the last time you cleaned the fins on the hot end?  Clean the cobwebs out of the fans?  

Common hotend or extruder problem summary

I've compiled a list of common hotend and extruder problems with solutions here. These are based on issues we've seen here over the years. It might be worth running through it just to eliminate the most common causes. If you discover something else, please let me know and I'll add it to the list.

Extruder clicking - Extrusion stops mid-print (Heat Creep)

Thank you @Dan Rogers for your reply!

The thing I don't understand is that these problems occur even outside the enclosure. I have been printing outside the enclosure for the last few weeks to test the impact.

I understand that at higher ambient temperature these problems occur, but I don't understand why it happens to me at 25 °C.About 4 weeks ago I disassembled the hotend, blowing off the heatsink with compressed air and scrubbing it with a toothbrush. I also removed the spider webs with tweezers.

I have already tested the tip with the lower bed temperature, but so far I have not ventured lower than 55 °C with PLA.

Maybe one more piece of information about the enclosure. I installed a vent this week in hopes of being able to print PLA with the door closed (for noise reduction).With the vent and the door closed, I manage an stable enclosure temperature of about 25 °C at 21 °C room temperature. Before the ventilation, the temperature was about 35 °C.

@bobstro Thank you for your response and your work!
I have already found your post, read it and also mentioned it in my initial post. It helped me a lot in understanding. Thank you very much for your work! Since I still could not find a solution, I decided to write here in the forum.

It worked at one point, so what physically changed?

Title is how I am thinking about what you are experiencing.  Good job on the enclosure vent.  I've got one that evacs at a set temp ... works great.  Your printer has worked at some point, that's my starting assumption.  Heat creep is not a normal factor - the printer does not come with that problem.  That's why I asked about the spider webs and cleaning the fins.  If the heat-input-system has not changed, I'm working on a train of thought that focuses on "why did the cooling capacity diminish".  Clogged/blocked air paths, therefore the first thing to check - which you have done.  Next up in the "keep checking the basics" checklist for me would be - did someone twiddle with the advanced tab on your slicer files?  While it may not be obvious, if the gcode is instructing the printer to NOT cool the hot end enough during the print, it will happily under-cool the print.  Get that check out of the way (not doing it now would mean we hold the obvious stuff to the very end - a waste of a lot of effort). 

After that - same train of thought - have your fans gone bad?  The fan to the left side of the MK3S extruder is not an infinite thing - they eventually wear out.  Something to think about, releatively cheap to eliminate as a possible cause.

Once you exhaust the "how come cooling capacity has diminshed" the only path left is "how come the heat-it-up system is over heating" - but that is for later.  It would be unusual for a heating element to grow hotter as it approaches it's failure point.  At least for more than a few prints.

Just out of curiosity, are you allowing the fan to cool the heat sync below 50C before you power the machine off when your done printing?

Regards

Swiss_Cheese

RE: Extruder clicking - Extrusion stops mid-print (Heat Creep)

Hey @dan-rogers I like your systematic approach and am very grateful that you are sharing with me about this issue and trying to help me.

The beginning of the problem
For me it's hard to pinpoint a time when the problem started to occur. Firstly because the problem only occurs with longer prints and lower layer heights and secondly because most of the parts I print are rather "short" prints with a layer height of 0.3 mm with a 0.4 mm nozzle. This combination is the best possible to avoid heat creep.

At the beginning of the year, I increasingly printed longer prints - also on lower layer heights of 0.2 mm and 0.15 mm. For the first time since I've owned the printer, prints broke off in the middle of the print.

Changes to the printer
After that, I started reading up and, based on my research results, I first exchanged the Prusa Heatbreak for a "normal" one without the 2.2 mm thickening. In my case it was a titanium one from Turmberg3D. Because of the fact some prints still broke off I exchanged the hotend fan for a Sunon MF40100V1-1000C-G99 LDO to have more cooling power. So I don't think the fan would need to be replaced yet. These two changes were in March this year.

Otherwise, I converted the MK3 to the MK3S and then to the MMU2S, but that was last year. I have not made any other modifications except maybe to switch to a Nozzle X.

Temperature of the extruder motor
One point I have also not looked at until now is the temperature of the extruder motor. I couldn't imagine until now that the extruder motor temperature could have a particularly large effect on it. I have seen solutions where cooling fins or even active cooling were installed but was not sure if it really makes a difference.
Reducing the motor currents could also be a solution, whereby the quality preset already has a reduced motor current. The last failed print was in the 0.15 mm quality preset. Even lower motor currents will certainly lead to too little torque at some point. But I have not tested that yet.

Prusa Slicer Settings and Fans
All settings in PrusaSlicer are otherwise at the default values. The part cooling fan is at 100% after the first 4 layers of my PLA prints and is not switched off afterwards. The hotend fan runs as far as I understand temperature controlled and is displayed with 7000 RPM during printing until the heatblock temperature is below 50 °C.

@swiss_cheese I let the printer cool down to below 50 °C in 95% of the cases before I disconnect it from the power. Since I have a MMU2S the filament is automatically unloaded after each print.

Maybe a workarround?
I have now ordered a Copperhead Heatbreak in the hope to realize a sharper tempreature transition to be able to print PLA better. After watching this video by Thomas Sanladerer I hope for similar results maybe even a 10 °C reduction in heatsink temperature. Unfortunately I don't have the right equipment to measure the temperature at the heatsink, but as long as no more prints fail I'm happy. Since the MK3S should actually print PLA at these temperatures without problems, the problem is surely somewhere else. Therefore it is more a workaround solution approach.

As soon as the heatbreak is here and I have made test prints, I will get back to you. Furthermore, I am very grateful for any advice on what I could still check.

You've covered the basics, a few other thoughts...

Posted by: @nivrix

[...] I understand that at higher ambient temperature these problems occur, but I don't understand why it happens to me at 25 °C. About 4 weeks ago I disassembled the hotend, blowing off the heatsink with compressed air and scrubbing it with a toothbrush. I also removed the spider webs with tweezers.

You've gone through the basics and your speeds shouldn't be a problem. I find it is sometimes enlightening to open the extruder, remove the nozzle, and run a 1.5mm rod with polished ends (I used brass rod from the hobby shop, anything 150mm/6in long will do) down through the open extruder, into the PTFE, down into the hotend and out the heater block. I encountered some internal machining defects on bi-metal heatbreaks I was experimenting with.

25C ambient temps should be fine, provided there is ample cool airflow for the heatsink cooling fan. Are you noticing any clicks or other mechanical noise in the lead-up to a jam? If this only happens with PLA, that certainly point to a heat problem. It prints well for hours, so a basic clog or plug is unlikely. Immediately after this happens, try heating the nozzle to the same print temperature, open the extruder, and manually push the same filament through. Does it feed and extrude smoothly? If so, "something" in the extruder may be contributing to your problems.

Grasping at straws:

• You mentioned thermal paste applied to the replacement titanium heatbreak. Only at the TOP where the heatbreak screws into the heatsink, correct?
• Are you using quality nozzles (E3D, P3-D, TriangleLab)?
• Is your extruder motor hot to the touch when this happens? I recently had an X motor failure, so it can happen over time.

REALLY grasping at straws here but...

In the old days when all-metal hotends were first produced, feed problems were common due to increased friction. It was common to "season" the hotend with oil. You shouldn't need to do this with an E3D with the short PTFE at the top, but... I admit to putting on a few drops on my Artillery Sidewinder when some of the clone parts caused problems. It's been smooth ever since. It might be worth replacing your hotend PTFE tubing while you're at it. If the internal surfaces are deformed or roughened, it might be that "just enough" added friction to cause problems with soft PLA. Feed a LOT of filament through and KEEP IT OFF YOUR PEI BED if you try this.

Uhm... here's a thought

Posted by: @nivrix

[...] What I have tried so far:

• E3D V6 Socks (have been in use for years)
• Hotend fan replaced with MF40100V1-1000C-G99 LDO (higher speed 7000 RPM, more airflow)

This is a bit of a long shot, but... is it possible you are OVER cooling? The sock should insulate the block and thermistor, but if some of that cooling is blowing on the nozzle or heater block, it can cause problems. You could try reducing cooling when the clicking starts. I'd expect to notice temperature variations (are you graphic with OctoPrint perhaps) if this happens, but it might escape notice.

And maybe...

A thermistor replacement might be worth a try. Sorry, keep encountering memory joggers throughout the day. I deal with these problems a lot on my other printers.

RE: Extruder clicking - Extrusion stops mid-print (Heat Creep)

@bobstro

I find it is sometimes enlightening to open the extruder, remove the nozzle, and run a 1.5mm rod with polished ends (I used brass rod from the hobby shop, anything 150mm/6in long will do) down through the open extruder, into the PTFE, down into the hotend and out the heater block. I encountered some internal machining defects on bi-metal heatbreaks I was experimenting with.

I will try that.

Are you noticing any clicks or other mechanical noise in the lead-up to a jam?

No, the clogging was not announced by noises and I'm pretty sure of that. During the last print I waited very attentively near the printer for the clicks. As soon as I could perceive a first clicking, I immediately initiated a filament change, after which it was possible to continue printing for a few minutes or hours. I loaded exactly the same roll of filament through the MMU again. So despite the problems I was able to complete my last 20h print with about 8 filament changes and minimal cosmetic errors.

If this only happens with PLA, that certainly point to a heat problem. It prints well for hours, so a basic clog or plug is unlikely. Immediately after this happens, try heating the nozzle to the same print temperature, open the extruder, and manually push the same filament through. Does it feed and extrude smoothly? If so, "something" in the extruder may be contributing to your problems.

It only happens with PLA. PETG and ASA working without problems. I tried extruding filament by hand after a clog and found that it works, but requires a bit more force at first. Apparently so much force that the motor does not manage to apply it.

You mentioned thermal paste applied to the replacement titanium heatbreak. Only at the TOP where the heatbreak screws into the heatsink, correct?

Yes only to the heatsink side.

Are you using quality nozzles (E3D, P3-D, TriangleLab)?

Only E3D never used a different brand. 0.4 mm Nozzle X is my main nozzle right now. I tested a brand new E3D brass nozzle with a problematic print because I suspected the Nozzle X. But it made no difference and the filamentment flow on all nozzles is in a straight line.

Is your extruder motor hot to the touch when this happens? I recently had an X motor failure, so it can happen over time.

Yes I would say the motor is already quite warm but I can not say how warm because I have not measured it. It is in any case colder than a heatbead at 60 ° C. But that the motor could be defective I have not yet considered. Do you think it might be worth trying to replace it? I guess a defective motor might be get hotter or has less torque or both.

In the old days when all-metal hotends were first produced, feed problems were common due to increased friction. It was common to "season" the hotend with oil. You shouldn't need to do this with an E3D with the short PTFE at the top, but... I admit to putting on a few drops on my Artillery Sidewinder when some of the clone parts caused problems. It's been smooth ever since. It might be worth replacing your hotend PTFE tubing while you're at it. If the internal surfaces are deformed or roughened, it might be that "just enough" added friction to cause problems with soft PLA. Feed a LOT of filament through and KEEP IT OFF YOUR PEI BED if you try this.

Thank you for the tip. I never used oil with the hotend. A few weeks ago I had disassembled the hotend and had there also the PTFE tube in hand. It still looked like new, but since I still have a new one here I will just replace it preventively. You mean feed a lot filament through after using oil?

I have a few things to look up and try. I will get back to you as soon as there is news. Thanks!

Posted by: @nivrix

[...] I never used oil with the hotend. A few weeks ago I had disassembled the hotend and had there also the PTFE tube in hand. It still looked like new, but since I still have a new one here I will just replace it preventively. You mean feed a lot filament through after using oil?

Do a quick Internet search. Vegetable oil is commonly used. This is not normally something that's needed with the E3D V6 hotend, but it might be worth one last try.

Definitely run enough filament through to pull out any oil lest it foul your carefully maintained PEI sheet!

So far so good - Heatbreak change

Thank you @bobstro for all the tips and hints!

This is a bit of a long shot, but... is it possible you are OVER cooling? The sock should insulate the block and thermistor, but if some of that cooling is blowing on the nozzle or heater block, it can cause problems. You could try reducing cooling when the clicking starts. I'd expect to notice temperature variations (are you graphic with OctoPrint perhaps) if this happens, but it might escape notice.

I have already thought about overcooling only I have ruled it out because the problem occurs after several hours and after the 4th layer nothing changes in the cooling. I've been using Octoprint since I got the printer, and I haven't seen any temperature fluctuations above ± 0.5 °C after the problem occurred.

Heatbreak Change - Maybe it works now

In the meantime my Copperhead Heatbreak arrived, I installed it and was able to complete the first problematic print. I think I need to complete a few more prints to be able to judge, but so far it makes me very happy.

I'll report back after a few more hours of printing.

RE: Extruder clicking - Extrusion stops mid-print (Heat Creep)

I too have your problem and I am going to try the Copperhead Heat Break. Can you tell me if you still went with the PTEF tube that comes with the MK3s that has the beveled edge or did you use one with a straight 90 deg cut?
Thanks

RE: Extruder clicking - Extrusion stops mid-print (Heat Creep)

@Padawg
I guess I have the default MK3S PTFE tube installed: https://www.prusa3d.com/de/produkt/hotend-ptfe-tube-mk2-5s-mk3s-mmu2s/

I first bought an MK3 and then upgraded it to MK3S, replacing the PTFE tube with the one mentioned above. I never did the upgrade to the MK3S+ or changed the PTFE tube seperately.

For self chamfering of PFTE tubes I found this tool here very helpful: https://www.thingiverse.com/thing:3773450

I hope the new heatbreak will solve your problem. Feel free to let me know if it worked!

RE: Extruder clicking - Extrusion stops mid-print (Heat Creep)

Thanks for the quick response.  I was more concerned with the other end which are tapered.  Its funny they only show the chamfered ones in the prusa store.  Tho I was able to do some more research and either the straight cut will work or the new tapered ones.  

I'll let you know.. again Thank You