Heated Thermal Runaway
Hi,
I've been printing happily with the MK2S/MM and I've had few real problems up until now...
I've been printing ABS for the last couple of weeks and everything's been working fine, but for the last four prints I've had the same error message "Heatbed Thermal Runaway" and the printer stops mid-print.
I have done a search on the forms:
http://shop.prusa3d.com/forum/search.php?keywords=bed+thermal+runaway
I have followed most of the checks:
1) the probe is still fastened securely underneath the heatbed.
2) the connectors inside the Rambo enclosure are fine for both the probe and the heatbed power
3) checked under the heatbed termination cover and the cable doesn't appear to be broken through fatigue.
4) updated to latest firmware (from RC1 to 3.0.12)
I haven't done the following two suggestions yet:
5) PID calibration on heatbed
6) upped the output power from the driver to ~12.5V
I haven't done those two yet because I've given up on it for today as I have other more important things to do (work.) Also, I don't see why a printer that's been fine for weeks suddenly needs it's voltage tweaking! I also need to borrow a multimeter since I don't have one.
I did sit and watch it print the last item with the USB lead connected to the computer so I could monitor the temps more accurately (that graph's so small it's pointless.) The bed temp obviously reached 100°C before starting the print, then I watched the temp drop to 96°C for most of the rest of the print before dropping slowly to 92.6°C. Strangely the temp increased to ~96°C moments before it decided to fail with the "Heatbed thermal runaway" message. All this took about 10 minutes.
I notice a few people have seen this message on the forums, and they've managed to fix it, so I'm hopeful, but I'm fed up with it for today. My observation of the temperatures makes me think that the heatbed doesn't have the power to maintain temperature, but how come for the last couple of weeks its printed several dozen ABS parts just fine???
Any suggestions or new info that I've missed would be most welcome.
Carl
Re: Heatbed Thermal Runaway
PID calibration was surprisingly easy:
http://shop.prusa3d.com/forum/original-prusa-i3-mk2-f23/firmware-3-0-10-just-released--t3343-s10.html
Afterwards the temperatures for both the nozzle & heatbed were keeping really constant -- for a bit anyway. Watching it print, the temperature for the heatbed would just steadily drop ~0.2°C per minute until it dropped to 94.6°C then (and I wasn't watching at this point) it triggered the "Heatbed Thermal Runaway" again. 🙁
It's as if it doesn't have the power to keep the heatbed at 100°C on top of powering the nozzle and motors too. Therefore, I'll try the voltage mod when I get a multimeter.
Carl
Re: Heated Thermal Runaway
I had the same problem, I upgraded to the latest firmware, still had the issue.
I upped the voltage a bit and that helped some, pid tuning also helped abit, adding some silicone baking sheet https://www.amazon.com/Artisan-Silicone-Baking-Half-Size-Cookie/dp/B00629K4YK under the printbed to isolated further improved the situation.
But when the psu gets hot and is under load the voltage drops to low to maintian 100C.
So no i set the bed temp to around 90C after the first layers
Re: Heated Thermal Runaway
The voltage mod seems to have fixed things and it's now running at a nice constant 100°C. So I'm pleased about that. 😀
What I'm not too pleased about is having to potentially void the warranty to make it do something it is claimed it should do unmodified - i.e., print ABS. 😥