MK2.5s Upgrade and Thermal Runaway - with my personal solution
So, I had a problem with this for over a week. After a lot of reading and reflection I finally figured it out. Posting here for anyone else that might find themselves in the same predicament that I had.
I upgraded both my MK2.5 and MK3 to the new "s" upgrade. On both printers I was also switching to the new tilted print fan for the first time. Both upgrades went well, but when printing the benchy and another model, my MK2.5S would always error out with a thermal runaway somewhere along the way. Particularly when a model reached a large flat point well above the heat bed. The MK3S acted somewhat similarly, but not quite as bad. I could not get a full model out without a thermal runaway error. WHAT??? Never happened before. What gives?
Tried this, tried, that no luck. Then I began to wonder... Both printers had problems in the past (one tumor, one broken heat break) that eventually led me to replace the entire hot end in both printers many months ago. Living in the US and not wanting to wait on Prusa, I bought genuine E3E v6 hotends from Amazon. Both came with a heater that had blue wires rather than the red ones that were original the the printer. Figured so what, blue wires, schmoo wires. Both printers did just fine with the new hot ends for months, so nothing to worry about.
After trying everything else, I did more research online and discovered that the "genuine E3D v6" hot ends are configured with 30 watt heaters now. The blue wires meant that I had 30 watt heaters in my replacement hot ends. The Prusa machines are sent with 40 watt heaters. I just swapped out the 30 watt heaters for 40 watt heaters and all of my problems are solved.
So, if you are getting thermal runaway errors because the heater cannot keep up with the print fan cooling, make sure you have 40 watt heaters. Even though the 30 watts heaters did just fine in both printers before the upgrade, they do not do so well with the improved cooling of the new design.
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
Just a comment. I have replaced the heater because of the same, the replacement came directly from Prusa and the wires are also blue. So the colour is not the identifier. Also the problem was not 100% solved with this. It was better, yes, but depending on printed objects, the thermal runaway appears from time to time again. What solved it completely was the silicon sock, Unfortunately the hontend is not delivered with the sock from Prusa.
Milos
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
Well, I guess all of our experiences are different. Main reason I posted was the fact that I saw no one else with the same issue I had.
I forgot to mention that when figuring my problem above, both MK2.5s and MK3s experienced thermal runaway after the upgrades. When I added a silicone sock, the MK3 did okay and had no further issues. The MK2.5s not so much. I would give a runaway error and just about every print. I replaced both heaters to the proper 40 watt to ensure factory spec. Of note, I did not put the silicone socks back on and now with 40 watt heaters, both are running just fine with no silicone sock.
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
I solved this problem (which showed only when printing PETG on a MK2S) by lowering the bed temperature after the third layer usign custom G-code in the Slic3r PE settings. After that I never saw it again. It reduces the sensitivity to temperature fluctuations since a lower temperature is easier to keep constant as it needs less power. I kept the code regardless of the filament and I experienced no problems so far.
In printer settings: "Custom G-code" - "After layer changed G-code"
;AFTER_LAYER_CHANGE
{if layer_z > 3}M140 S65{endif}
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
I would just like to add my findings too to thermal runaway.
After upgrading from MK2.5 to MK2.5S I noticed that I was getting heat error/thermal runaway, but not with petg, only with PLA. This never happened before my upgrade.
Whilst watching the printer print in PLA, I noticed that once the first layer was complete, and the printers part cooling fan increased to 100%, the extruder heater was unable to maintain the correct temp due to the more effective cooling.
After changing the fan speed to 60%, as is in PETG, this was no longer a problem. So too much cooling on the hotend.
I've read that other users suggest a silicon sock. I will put one of these on and retest with the fan at 100%.
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
I did not read the whole thing in details, however I wanted to suggest that
;AFTER_LAYER_CHANGE
{if layer_z > 3}M140 S65{endif}
would cause the commands to run on each and every layer after the third....
it might be better to use:
;AFTER_LAYER_CHANGE
{if layer_z = 4}M140 S65{endif}
Eyal
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
I started with an equality condition and it didn't work. The printer failed to act on it regardless of the slic3rPE version, all the while printing from the SD.
I tried a number of times after the initial tests and it just doesn't happen. In the end I kept the inequality since the temperature doesn't actually change and the command doesn't cause any extra wear or wait time.
On a side note, editing G-code in those edit boxes is almost impossible (slic3rPE). After a key is pressed the text in the window scrolls to the top while the caret remains at the editing point. Doesn't seem to happen in Prusa Slicer v2.0.0 though.
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
These entirely false THERMAL RUNAWAY alarms is IMHO really due to the code detecting thermal runaway too naïve, not understanding the effect of the filament cooling fan. I have made a fix that I believe repairs the problem, so you get rid of the problem for good. I have only tested on my Mk2, but I see no reason why it should not work on the other variants too. https://forum.prusa3d.com/forum/original-prusa-i3-mk2-s-general-discussion-announcements-and-releases/fix-for-thermal-runaway-problem/
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
As I have said several times and still use it successfully, Kapton adhesive tape helps.
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
I also had the thermal runaway issue, when printing PLA and the fan kicks on when starting on the 2nd layer, after upgrading my printer from MK2s to MK2.5S. Adding the silicone E3D Socks as suggested above fixed the problem for me.
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
@jeraymond
Yep, same here. Simple and effective.
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
Thanks for all suggestions from above. Just started having the same thermal runaway issues here. Has been fine ever since the upgrade from MK2 to MK2.5s a month or so ago. But weather has been really hot here, so was working with room temp about 33- 35 deg. Has now cooled to 28, and had 3 runaways in a row, always on the second layer. Will try setting the extruder fan speed lower, thats easy.
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
Sorry, I meant to say model fan speed, not extruder. And yes, running the fan at 60% of max speed seems to work fine for PLA and a room temp of 28 deg.
You can evidently adjust this even during a run, using the manual Tune facility, if you start to see the nozzle temp drop below the set temp. Be aware though that it may revert to the preset speed after a layer change. Note that the Tune facility sets the speed in the range 0-255 units, corresponding to a percentage range of 0-100%.
In fact there are several settings in the Prusa slicer you can use to auto adjust the fan speed, depending on the number of layers, print speed, etc.
It also occurred to me that the shroud around the fan nozzle could probably be improved. At the moment it seems to direct most of the air over the hot end, rather than the model, which is where its really needed.
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
I'm having the same issues with my newly upgraded Mk2.5S. I've even lowered min/max fan speed to 20%/30% and I still get thermal runaway crashes. I've ordered an E3D sock, so I'll report back if that makes a difference (which it seems to, based on what I read here). I hope Prusa makes some design changes either to the fan shroud or the firmware, or both.
My firmware is 3.8.1-2869. I'm slicing on PrusaSlicer 2.2.0+win64.
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
@george-b2
I just did the same thing as you, "upgraded" to the spare blue lead heater cartridge I had lying round while upgrading to mk2.5s and thermal runaway on 2nd layer. Its 30W it says on the cartridge and the E3D site. Put the old 40W one back in and boom problem solved. Thanks heaps for posting this, saved me hours!
RE: MK2.5s Upgrade and Thermal Runaway - with my personal solution
UPDATE: I put the blue silicone E3D Socks on in April and have not had any trouble with thermal runaways since. I'm still on my first (with a little over 400 hours of printing), though there is a small tear on the bottom. The package I ordered had 3 socks, so I'm set for the foreseeable future. Would still like Prusa to update the fan shroud design, but I consider the E3D socks to be the working solution to this issue.