Source
r/3Dprinting•
RandomUsername55

Thermal Runaway Error Prusa MK2

Discussion

Hi guys and gals, I've been battling a thermal runaway error for about a week now and I'm all out of ideas.

Basically, I'm able to print the first layer without issue, but as soon as I start the second layer, the nozzle temperature begins dropping. I've looked for shorts in the thermosistor and heating elements at both the nozzle and inside the electrical box, but found nothing. If I heat the nozzle and let it sit for an hour, the nozzle has no problem staying at temperature. The PID has been recalibrated, the heatbed heats just fine, temperature calibration has been run successfully, and out of curiosity, I re-sliced the program (using Slic3r) various ways, all to no avail.

What else should I be looking at? I'm open to any ideas at this point.

Thanks!

Posted Apr 29, 2018, 8:54 PM UTC

09
zombieprimeCL-260•

Have you ran PIDTUNE with the part cooling fans on?

2
RandomUsername55OP•

I've run the PID tune with the cooling fans running at the same nozzle temp and fan speed as during my print.

The first layer of my print takes approximately 35min, so I would assume if the fans were an issue, I would have a problem prior to my second layer.

Additionally, I've tried running other prints with shorter cycle times, but again, the second layer is when I lose temp.

1
zombieprimeCL-260•

I had that problem a few days ago. I would thermal runway right after the second layer, instead now my part cooling fans turn on after the 3rd layer, no more thermal runway errors

pretty much the fan blew too much air, hitting the bed and blowing back at the nozzle

3
RandomUsername55OP•

I'll take a stab at turning the fans on later in the print and report back. Thanks!

1
careless__•

i've found that depending on duct design, a strong 50mm fan has the power to trip thermal safeties no matter what PID tuning you do. obviously, those ducts can have their design improved- but if you want to get around it, I've found that ramping up the fan speed over the first 5 layers from 0 to 100% seemed to solve the issues and give the nozzle enough time to recover from the fan air blowing gradually rather than so abruptly.

2
zombieprimeCL-260•

no problem!

1
Hey_Allen•

Like zombieprime suggested, try running the time with your fan on at the speed that it would be when printing, or a little higher if you don't normally run them at 100%.

I did the same thing, the first time I tuned my pid settings, and scratched my head about it until realizing that the pid tune was expecting a static load condition, rather than the dynamic condition that the heater experiences while the fan is running and filament is flowing through it.

Edit: auto-"correct"

2