Crazy fan causing THERMAL RUNAWAY
Hi all!
So I recently bought a second hand mk2(upgraded to S) with an odd issue.
After a few layers the cooling fan starts blowing way too hard and cools so much that it causes a thermal runaway.
Now if I stay with the printer and keep turning the fan speed back down then everything is OK. But if I leave it she'll just keep going up into the 250's. The highest I've caught it at is 259. Also, it will keep blowing at this speed even after the print has finished.
So my question is, how is it that I slice a model with lets say max fan speed at 100% but once printing starts she shoots up to 250%???? What could be causing this and does anyone have an idea how to fix it?
Thanks! 😉
Re: Crazy fan causing THERMAL RUNAWAY
Does it do this on pre-sliced files from PRUSA, or only on the ones you slice?
What version of the firmware are you running? Did you do the PID calibration?
What slicer are you using? (including version number)
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Re: Crazy fan causing THERMAL RUNAWAY
So my question is, how is it that I slice a model with lets say max fan speed at 100% but once printing starts she shoots up to 250%???? What could be causing this and does anyone have an idea how to fix it?
The speed you are seeing in the display is not %. The fan speeds are from 0-255 so, 100%=255, 50%=127, etc.
Re: Crazy fan causing THERMAL RUNAWAY
The speed you are seeing in the display is not %. The fan speeds are from 0-255 so, 100%=255, 50%=127, etc.
Yes! I came to this conclusion myself a couple hours ago while trying some ABS. Slic3r PE ABS settings have the fan at 30% for bridges so I checked what the fan was at during a bridge and then just did the math.
The problem does seem to be on the Prusa end due to their PLA print settings as detailed at the bottom of this page:
http://help.prusa3d.com/mk2-electronics/thermal-runaway-and-temperature-drops
The problem also occurred when I tried to slice my own benchy in the latest version of Slic3r PE so I guess they just forgot to fix those values. Which means anyone trying to print PLA with the default settings will experience the exact same problem.
Well at least that's that mystery solved. Next up I have to investigate a non-working heatbed LED 🙄
Re: Crazy fan causing THERMAL RUNAWAY
When I'm printing with PETG, if it is a small part then the fan itself is turned off. Otherwise with the fan on, it will drop the bed temperature too much. For most pieces I never use the fan with PETG. In some cases the fan is set to not turn on until at least the 20th layer and only at 30% but I usually have it off. I had no more issues after that.