Okay, how do I really fix the "Bed Thermal Runaway"
Hi all,
I've had my Prusa MK2 since February and it's been printing both PLA and ABS perfectly fine up until two days ago.
After finishing an ABS print, I started up a new one, only to have it stop after the first layer with a "Bed Thermal Runaway" error on the LCD.
I tried again, and got the same message.
I've been Googling and trying different things ever since to no avail and it doesn't sound like any of the myriad other users who have had this problem actually get any resolution? Did you all just buy new printers?
Here's what I've checked/done:
2) I checked the soldering at the heat bed. I even moved the cable up and down to see if the LED turned off indicating a break in the wire - nope, no break. Solders nice and solid. Also, the LED stays on during preheat and printing. Sometimes it blinks rapidly, sometimes it's solid. Not sure what the difference is.
3) Checked the thermostat below the bed. Nice and tight. And since it prints PLA just fine at a consistent 55 degrees, I think that's okay as well.
4) Ambient room temperature is around 72 degrees, but not sure that would be a problem since it was printing ABS perfectly fine up until a couple of days ago.
5) I recalibrated the entire machine, mesh bed leveling, XYZ calibration, and ran the self tests - everything came out normal.
6) I successfully printed the triceratops skull and Marvin the martian in PLA - zero problems, and bed maintained its temperature throughout.
7) I checked the Slic3er settings as well. Keep fan always on, unchecked. Enable auto cooling, unchecked. Bridges fan speed: 30%, although, when watching the ABS print fail, the fan doesn't come on at all - so I don't think it's that.
I just emailed Prusa, unfortunately I couldn't find a support contact and the live chat seems to have disappeared. I'm hoping it's something simple, and worse case they stand by their product and send me a replacement part.
So, fellow printers. Who of you has dealt with this and successfully fixed it? The last thing I want to do is start tinkering with soldering stuff. And like I said, nothing is melted or appears to be damaged.
One other thing to note, not sure if it has to do with anything however a couple months back I damaged the top of the heat bed (scratched it). I've printed a lot since then which is why I don't think it has to do with anything, but figured I'd put it out there.
Thanks,
AP
Re: Okay, how do I really fix the "Bed Thermal Runaway"
Unwrap the cable bundle and check the full length of the thermistor cable for a break. If you don't find one, use the LCD menu Settings | Temperature to set the bed temperature to 100 and monitor it with the bed stationary. With the bed hot, move the cable bundle around and see if you get either the warning or a loss of temperature, do take care not to touch the hot bed.
If the temperature holds with the bed static but something goes wrong when you move the cables, you have proved a broken cable, and just need to track down the break. If the bed cannot reach temperature, you possibly need to change to a new bed, but the thermistor could be faulty and is much cheaper to replace so try that first.
You can only see the chat on the shop page when you are logged in to your shop account.
As an aside, I am amazed at how many people actually trust google to
a) provide any information
b) provide factual information
Bill
Tagaytay City, Philippines
Founder member of Philippines Prusa Printer Owners FB Group
Sponsor Pillars of God Academy in Bacoor