Thermal runaway
I completed the Mk4/Mk4S upgrade on Monday. All tests passed except the nozzle heating. After reading here, I removed the silicone sock and the test passed. I tried a simple print and after a couple of minutes received a thermal runaway error. I contacted Prusa support and did some testing including swapping out the HF nozzle with my old one. Support got back to me with the usual beginner questions. In the meantime, my testing revealed that the error occurred only after the print cooling fan came on. Support asked for some pictures of the print head and suggested it might be a cooling fan issue. After the print completes the first layer and the fan turns on, the temperature drops (230C -> 220C for example), but doesn't stop. The error occurs when it gets below 200C.
I reinstalled the silcone sock thinking it might provide some insulation. It did and the printer works extremely well now. In the meantime, support has not replied to my repeated emails (last one was early Wednesday). I know I can print with a silicone sock, but I think the printer is supposed to work without it. I'm at a loss as to what the problem might be. Bad heater block, insufficient power (wiring issue)... Any ideas on where I might look or what replacement part I should order?
Or should I try recontacting support with a new ticket? Thanks for any tips or hints you can supply.
RE:
I have had this issue while printing petg. I read somewhere, based Prusa advice the solution was to print another object away from the print. So I too would like to get to the bottom of this issue.
Note: I have an mk3S+
i3 Mk3 [aug 2018] upgrade>>> i3MK3/S+[Dec 2023]
RE: Thermal runaway
You know that on the MK4 there is an option for the silicone sock in the display menu somewhere under hardware setup, right? You must set this option correctly according to the fact if you have the sock installed or not. Setting this option the wrong way could cause problems with the heating control.
RE: Thermal runaway
Yes, I’ve been aware of that setting since I upgraded from my Mk3S to a Mk4 last November. It was set correctly for all my testing.
RE: Thermal runaway
Very interesting thread.
I completed my upgrade from MK4 -> MK4S. All went well, all calibrations spot-on so time for a first print with the new setup. I selected something I have done many times before: a Gridfinity 4x3 base using some PLA Pro I have been trying to use up. I am using Octoprint to control the printer and fired off the print. First two layers went perfect. The new big fan shows a zero pct and the tool temp at 220/220, bed at 60/60. All good.
Then, the third layer starts. Fan jumped to something like 35% and the tool temp starts to fall. And it falls quickly. As the third layer completes the fan kicks up to 75% and this is where the temp runaway happens. The hotend never recovers and the printer shuts down.
I DID NOT have the sock on. Never have had the need for socks, so I left it off. Well I figured the new fan is so powerful it cooled the hotend as well. This is when I added the sock, then went to Settings -> Hardware -> Nextruder Silicon Sock and turned it ON. Ran calibrations and all good again.
Then, I started the same print. This time, no temp deviation. It stayed right on the money between 219-220 and the print completed as expected.
So question: is the sock a 'must have' item now? Or is there some setting I am missing here? That new fan really must blow a strong cooling blast that it is affecting the hotend temp. Prusa folks... Is this normal?
Regarding the 'socks'... I see they are available but darn, placing an order just for genuine Prusa socks is going to be quite expensive to justify the shipping cost to the USA. Anyone recommend a good quality sock? Or it doesn't matter?
Very curious to see what others are doing to solve this issue...
RE: Thermal runaway
Prusa support finally got back to me this morning:
"Could you please provide me with the order number related to your original Prusa MK4 printer?The issue might be in the thermistor or heater, which could have send incorrect data to the printers motherboard to process them."
I'll keep this thread updated with any new information I receive.
RE: Thermal runaway
Regarding the 'socks'... I see they are available but darn, placing an order just for genuine Prusa socks is going to be quite expensive to justify the shipping cost to the USA. Anyone recommend a good quality sock? Or it doesn't matter?
I was going to suggest checking PrintedSolid for nextruder socks, but I was unable to find them there. I did find a US vendor selling Prusa branded socks for the nextruder for about $10USD for a pack of 3. I haven't personally used them as a vendor, so I can't attest for the quality of their products. They claim to ship out of Ohio.
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs
RE: Thermal runaway
My Mk4 (upgraded from a Mk3) is still under warranty, so Prusa sent me a new hotend thermistor and heater which I installed this morning. Reran the heater test (passed) and tried a simple print without a sock. 1st layer temp was 230C, subsequent layers 225C. After the 1st layer, the print cooling fan kicked in and the hotend temp dropped immediately to 215C. It slowly made it back to 220C, but no higher. By the forth layer (printing infill), the temp slowly dropped to 205C and then quit with a thermal runaway error.
Reinstalled the sock and it prints fine again. Since the heater and thermistor seem to work great without the cooling fan running, about the only thing left to try is the heater block. I wrote back to Prusa support and I'll have to wait to see what they say.
RE: Thermal runaway
I just upgraded from MK4 to the plus. I am experiencing the exact problem described here.
I don't believe the MK4S prints as well as the MK4. On my MK4 I found that when printing with PLA ,it did better without the sock. I tried several times to print without the sock on the MK4S to see if the machine would print better. I got the thermal run away every time.
Once I finish my current project, I plan to remove the high flow nozzle, and go back the regular nozzle. And of course, slice with correct nozzle settings.
RE: Thermal runaway
Now I am getting nozzle heater calibration errors!!!
RE: Thermal runaway
Now I am getting nozzle heater calibration errors!!!
Don't forget to change the setting in the printer for sock on/off. I'm not in front of my printer at the moment, but I think it might be under Settings/Hardware/Nextruder, but I could be wrong.
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs
RE: Thermal runaway
Thank you for the reply. Before I upgraded from mk4 to mk4s I preferred to print PETG with the sock, PLA without. I saw less stringing. There for I am familiar with this setting. After upgrading to the 4s, I was not happy with the print quality, therefore I started experimenting with print printing without the sock. I got thermal runaway errors. After reading other post posts about the temp dropping after the second layer, when the new nozzle fan kicks in, I thought the thermal runaway was going down, not up.
At this point I tried to “undo” the upgrade to 4s and tried to print, I got worse results. So then I put the upgrades back on to the nexteuder, I noticed that when I was mounting the nozzle fan that there are slots in the fan housing that the mount slides into. I am pretty sure the first time I had the mount on the outside of the fan housing. The screws fit a lot better. I brought the printer back up and Set it back to a mk4s and ran the calibrations. This was when the nozzle temp calibration failed. I ignored it and I was was able finish printing the project that I had started. It actually printed OK, not great, but it didn’t fail.
But I am pretty sure that I fried 2 nozzle temp sensors. When upgrading to the 4s, in my experience, using the sock is absolutely required!
I ordered a couple more sensors. To be continued…
RE: Thermal runaway
Prusa asked me to remove the fan shroud and take some pictures of it. After I sent them, they got back to me with:
"We have checked your case with our colleagues from testing department and the silicone socks is required for the MK4S printer with a 360 cooling fan, as it can cool down the heatblock much quicker than the previous side fan shroud.From now on, please keep the sock on the heatblock, with the option in menu enabled and the issue shouldn't appear again.I do apologize for tha initial confusion."
So, I guess they're now requiring a silcone sock for the MK4S new cooling fan. I know a lot of people have had the same thermal runaway problem I've encountered, but some must be able to print without a sock. I'll just continue using the sock since it keeps the block clean and doesn't appear to impact printing.
RE: Thermal runaway
I just made the same experience: thermistor error without silicon sock. The bad side: it is not mentioned in the assembly ore user guide, that you need one. It took a couple of trial&error for me to figure it is just the sock and no wiring or sensor issue.
RE: Thermal runaway
Prusa support finally got back to me this morning:
"Could you please provide me with the order number related to your original Prusa MK4 printer?The issue might be in the thermistor or heater, which could have send incorrect data to the printers motherboard to process them."
I'll keep this thread updated with any new information I receive.
This answer from Prusa really grabbed my attention. I've had a thermal runaway problem with my MK4: https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4-hardware-firmware-and-software-help/thermal-runaway-on-some-prints/
I have the 4S upgrade kit, and the MMU3. I'm in for an adventure it seems.