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Random Thermal runaway errors  

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brent.p
(@brent-p)
Eminent Member
Random Thermal runaway errors

I have been fighting this problem for over a few weeks now. Thought it was related to the temperature in my room being different to the rest of the house. That was proven wrong by keeping the door closed.

Sometimes the prints will have zero fluctuation in temperature and other times it will go all the way down to 185 and back up to 220. This doesn't happen on everything I try to print. My guess is the thermistor is bad, but honestly I have no clue. I have tried all the quick things like checking for pinched wires, made sure it's not loose, reseated it, wires not touching etc. Extruder and temperature have been calibrated already.

Has anyone experienced this or can point me in the right direction? I am at a complete stop as it's just too unpredictable to risk printing something for hours only to have the temperature fluctuate and give me a thermal runaway error.
The printer is an MK2S that I have only had for just over a month.

Posted : 07/05/2017 11:21 pm
brad.b3
(@brad-b3)
New Member
Re: Random Thermal runaway errors

are you printing in quiet mode? If so try printing it in the normal mode, not quiet.

Posted : 07/05/2017 11:38 pm
brent.p
(@brent-p)
Eminent Member
Topic starter answered:
Re: Random Thermal runaway errors

No I don't print in quiet mode.

I just turned my printer on and now it says Mintemp whatever that means.
Nozzle is at 11
Bed 25

Maybe this is related to all my temperature issues.

Posted : 08/05/2017 12:00 am
maxx78
(@maxx78)
Estimable Member
Re: Random Thermal runaway errors

Check the cable of thermistor. Mine broke on the plug between the thermistor and the cable to the Rambo Board.

Posted : 08/05/2017 11:12 am
brent.p
(@brent-p)
Eminent Member
Topic starter answered:
Re: Random Thermal runaway errors

More bad news. I was able to get the thermistor out finally. Not without breaking off both wires to it. The thermistor was completely stuck inside the block. Upon removal I discovered a large indent on the thermistor where someone screwed in the screw too tight.
Honestly I am very disappointed with the printer. The printer has only been in my possession a little over a month and it's been one thing after another.

Dead fan, damaged thermistor, ptfe tubing not installed correctly. All in the matter of a month. Granted I am brand new to 3d printing, but I would have expected the quality to be a little better.

I think support has heard enough of me and I don't feel like bothering them all the time over every little thing I find.

The quality of prints is very good when it is working.

Posted : 08/05/2017 11:24 pm
dapug
(@dapug)
Eminent Member
Re: Random Thermal runaway errors

I too am having Thermal Runaway issues and I cannot identify why. I've had my Prusa i3 MK2S for about a week.

I can print PLA just fine, no issues, works great!
I cannot print ABS! Thermal Runaway every time.

Thermistor is fine so far as I can tell. PLA would not print if there was a physical/wiring problem. Is it possible that the room temp drops too much? Walking past the machine might cause a wee breeze, but is it really that sensitive? Do I need an enclosure?

I did notice that the bed has a VERY hard time getting to 100, but I assume only the nozzle temp is factored for Thermal Runaway issues. The nozzle appears to maintain 255 just fine as expected. I even see Thermal Runaway when the nozzle hasn't shown a drop in temp. VERY CONFUSED.

What is the deal with Thermal Runaway on the Prusa?

Posted : 09/05/2017 5:59 pm
Print McPrinty
(@print-mcprinty)
Active Member
Re: Random Thermal runaway errors

Same here, I can print PLA just fine but I get the error when printing with hotter ABS.

Posted : 09/05/2017 7:53 pm
JuanCholo
(@juancholo)
Reputable Member
Re: Random Thermal runaway errors

lower cooling fan speed. the extruder cannot keep up with the cooling you want.
drop in 5% increments until the thermal runaways stop.

you can see this on the display you are trying to hold 255 and the display says 240/255 that is a 15 degree difference and will trip the thermal runaway safety.

you could also drop the extruder temp 5C that gives you more capacity to hold.

“One does not simply use a picture as signature on Prusa forums”

Posted : 09/05/2017 8:39 pm
dapug
(@dapug)
Eminent Member
Re: Random Thermal runaway errors

Plagued with Thermal Runaway still, even after the latest firmware (3.0.11). Specifically it is the Heat Bed that has the issue, not the nozzle.

  • Start a print with ABS (100c bed temp)

  • Starts out ok, bed reaches 100c fine (painfully slowly, but it gets there)

  • I watch the graph as it prints, steady for a while, but then see a slow taper down to about 85c

  • BOOM - Thermal Runaway
  • Why??? I've even done the mod on the power supply for 12.6v. If I run a preheat right after this failure, it reaches 100 again fine, so it's not like it is incapable, and clearly not an issue like a bad connection, etc. GRRRRR

    Posted : 27/05/2017 7:15 pm
    GertL
    (@gertl)
    Reputable Member
    Re: Random Thermal runaway errors

    My thermistor did go loose.
    The first thing i noticed that it took about 20 minutes to get to 80C.

    ---
    Gert

    Posted : 27/05/2017 7:26 pm
    dapug
    (@dapug)
    Eminent Member
    Re: Random Thermal runaway errors

    I thought the thermistor for the bed is built in. I'n not seeing what can go loose here. This isn't a user serviceable connection on the bed, the only part we mess with besides the actual connection into the RAMBO is the tie wrap on the bed wiring, everything is secure.

    Posted : 27/05/2017 9:40 pm
    GertL
    (@gertl)
    Reputable Member
    Re: Random Thermal runaway errors

    Have a look here:
    http://shop.prusa3d.com/forum/original-prusa-i3-mk2-f23/thermistor-came-loose--t4387.html#p32607

    ---
    Gert

    Posted : 28/05/2017 9:31 am
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