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TonyTDMD
(@tonytdmd)
New Member
Thermal runaway (low temp extruder)

Finished my mk3 2 weeks ago and the prints have been perfect, until now. After a 60 hour print, the next prints have all had thermal runaways (low temp on the extruder), generally after the first layer as soon as the part cooling fan comes on, temp drops and it can’t seem to compensate. Checked connections and did PID calibration. The temp swings in octoprint seem more extreme than they were at first too. Bad thermistor or heating cartridge? Thanks

Posted : 21/07/2019 9:45 pm
Dave Avery
(@dave-avery)
Honorable Member
RE: Thermal runaway (low temp extruder)

or changing room temp

Posted : 21/07/2019 11:43 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Thermal runaway (low temp extruder)

you should not combine high temperature with fan full speed. After a lot of tests on my printer i found following results:

255 (fanspeed) 100% (fanspeed) 232⁰C (temperature)
230 90% 236⁰C
204 80% 238⁰C
179 70% 258⁰C
153 60% 277⁰C
128 50% 298⁰C
102 40% 305⁰C
77 30% 305⁰C
51 20% 305⁰C
26 10% 305⁰C
0 0% 305⁰C

that means: with fan full speed (255 or 100%) my extruder reaches a max. temperature about 232 degree celsius and when i reduce to 40% extruder reaches full temp (295-305 degree celsius). if you exceed these limits you will get: "Thermal Runaway".

Try to find a rational combination between fanspeed and nozzle temp.

with best regards

Karl

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 22/07/2019 8:48 am
bobstro liked
RH_Dreambox
(@rh_dreambox)
Prominent Member
RE: Thermal runaway (low temp extruder)

You can also apply a Silocone Sock to the hot end.
It eliminates temperature drops and reduces the risk of filament blobs.

 

Bear MK3 with Bondtech extruder...
Posted : 22/07/2019 12:18 pm
Crypto liked
TonyTDMD
(@tonytdmd)
New Member
Topic starter answered:
RE: Thermal runaway (low temp extruder)

i Can’t figure out why it worked perfectly for weeks, and now this problem, it’s driving me nuts! Last night I sent the printer a job with maximum 30% fan. Failed after an hour or so. 

Posted : 22/07/2019 3:26 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Thermal runaway (low temp extruder)

in most cases it's a hardware-problem. You could check the thermistor, heater. You should also check the hotend for blockages, rests of filament scraps....

After that make a pidtuning (bed and nozzle calibrate). I wrote a shell script, which you can use to set the right parameters for bed- and nozzle temperatures. To run the script you need Octoprint, otherwise it will not work.

 

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 23/07/2019 11:52 am
TonyTDMD liked
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Thermal runaway (low temp extruder)

pidtuning

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 23/07/2019 12:00 pm
TonyTDMD liked
TonyTDMD
(@tonytdmd)
New Member
Topic starter answered:
RE: Thermal runaway (low temp extruder)

OK, tried new thermistor, same problem. Tried new Heating element, same problem. Prints either fail as soon as fan kicks on, or about an hour into print, with it acting like the heating element suddenly has no power. also tried silicone sock. Im out of ideas and patience.

Posted : 26/07/2019 12:16 pm
TonyTDMD
(@tonytdmd)
New Member
Topic starter answered:
RE: Thermal runaway (low temp extruder)

Heres where I just happened to catch it Crashing

 

Video-1

Posted : 26/07/2019 1:31 pm
RH_Dreambox
(@rh_dreambox)
Prominent Member
RE: Thermal runaway (low temp extruder)

On the video, it looks like the heating element is switched off and the temperature is dropping rapidly because of it.
If you have changed the heating element and the cables are intact then you should probably look for the problem in Octoprint.
But if you print from a SD card, everything should work as normal.

Bear MK3 with Bondtech extruder...
Posted : 26/07/2019 2:25 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Thermal runaway (low temp extruder)

could you post the gcode and the P.I.D. values (report with M503) from bed and nozzle?

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 26/07/2019 5:15 pm
swizzler121
(@swizzler121)
Active Member
RE: Thermal runaway (low temp extruder)

Did you ever find a solution to this? my unit is doing the same exact thing, printing from SD. Just posted a topic on it as I wasn't finding any similar issues until I found this post.

 

 

Posted : 03/08/2019 8:56 pm
Crypto
(@crypto)
New Member
RE: Thermal runaway (low temp extruder)

I've been getting the same thing on and off especially when doing large areas on the second layer where it's extruding really quickly. My theory is that the filament is heat sinking the heat away and when you couple that with the fan coming on for the second layer it just can't keep up.

I've now been dropping my nozzle temps from 215 deg to 205 and it seem to be working. Got a sock on order though 😀 

Posted : 15/08/2019 11:17 pm
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(@)
Illustrious Member
RE: Thermal runaway (low temp extruder)

This FAN ON thermal runaway is a fairly simple problem to solve. As stated above, add the silicon sock the the heater block.  This prevents the blast of cold air slowing the heating process.  But at the same time it is important to perform a PID calibration that the temperature you plan to print at the most.   This allows the controller to figure out the power and temp rise characteristics of the hot end and allows for much better control; and a better estimate of when the applied power isn't heating "enough" to flag a thermal runaway.

Posted : 16/08/2019 8:20 am
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