Bed Thermal Runaway

Well, nice to know the systems are working. Now the question is repair or replace? A print stopped halfway through with a bed runaway error and it won’t heat up now. (Error attached). The screen is showing the indoor temp on the bed and nozzle.

Where does a guy start with this one? Do finally get a new bed? ;)[attachment file=94469]

Could be a few things. If it is below 5C it will not work (you get that error, unless you edit the firmware), if it is really cold your bed might not be able to keep up and a Mains SSR version might be a better choice.

I agree with Ryan. It could also be a loose wire. The board may have turned the heater on but if the wires are not connecting to the heated bed then nothing will happen. after a short time of the heater being turned “on” and the temperature not rising this error will pop up.

So did the heated bed go cold? will it heat at all? Is it just not keeping up?

The wires get moved a lot during a print. Something could have just come loose.

Right you are. The positive that goes to the bed (at the bed) wore loose or wore and broke. I’ll tear it apart this evening and see how I’m going to fix it (I’m assuming it fixable). I had poked on the wiring but that’s a tight bend on my printer and it wasn’t until I pulled and poked that it was apparent.

I’m assuming that if this broke mid-print (which it did) and the board was trying to send voltage to add more heat to the bed but it wasn’t registering any effect it triggered the thermal runaway? Is that right?

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Yes if any heater is not within a few degrees plus or minus of where it should be it shuts down.

What do you all think re-tin the wire and hope for a good solder connection? I think I have the skills…it doesn’t look or smell burned up - most certainly looks like it was just a wiggle wear out. I see one protruding screw that might touch it just enough as it passes by on Y axis moves.[attachment file=94540]
[attachment file=94541]

Yeah. That should be easy to solder/re-tin.

Then you will want to find a way to support the wires so this doesn’t happen again. On my old i3 Migbot (Similar to the MP3DP) I rotated the heated bed 90 degrees so the wires were connected to the side (instead of the back). Then I used kapton tape to secure the wires to the edge of the bed the rest of the length of the bed so the wires would still stick out the back. There are more elegant solutions but it worked for me for a while.

Other people probably have some amazing solutions with cable chains and stuff.

Um…is that like special high temp solder or something? I can’t even get a cold weld out of it…and I’m using a nice high/low power iron…

Going to borrow a friends butane torch tomorrow. Best all my Googling came up with. Any idea how I can protect the LED right beside the solder pad?

No no no, don’t do that!

No blowtorch on a heating bed, you’ll destroy the bed and ruin everything, plus the solder will just burn.

Get a proper soldering iron and use soldering flux

I think my soldering station is “proper”, just not strong enough (40w on high setting). Maybe I’ll try heating it through with the Ender bed and then see if I can get the solder to melt.

Yeah a preheat before your next attempt should go a long way. It takes a lot of juice to solder that large of a pad to an aluminum plate, it sucks the heat out instantly.

Okay I got it. I set the under bed to 88 (don’t ask where I got that number from…just didn’t want to go over 100 and risk the magnetic issues I’ve read about). It looked promising but still little underpowered in the soldering iron department so I used a MAP torch to super heat the soldering iron tip and that did the trick. Quite well in fact. the bead looks nice 0 pretty confident it’s not a cold weld. I’ll update success or lack thereof when I get it back together.

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Interesting development. Usually my 40w iron is enough but not always. If I lived closer I would let you borrow my 100w soldering gun. I have only ever used it to remove solder from some boards and to repair the connection to the thermalcouple on my water heater.

Ok, here are some other creative ideas. Not sure if they are good just creative:

  • Use a sharp chizel or something to scratch the solder off. This could result in ripping the pad off the board.
  • Borrow the blowtorch but don't use directly on the solder. Try using it to heat your soldering iron a little more.
  • Use a grinder, dremel, hack saw etc..
As long as you remove enough of the old to allow yourself to get a good new connection you will be ok. You should be ok just using your normal solder/tin when you connect your wire again. My old i3 Migbot used a MK2 heated bed as well. I used normal solder/tin on it and was able to get the bed up to 95 C consistently. it held fine.


EDIT: you beat me to it. Nice work.

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So far so good. I guess we won’t know until it’s run for a while but the wires are all well secured to the speed plate again and no obstruction at all. I cut back the offending extra length screw.

[attachment file=94635]

Hey Kelly, I found this posting, good thing your printer has thermal run away.

you could have texted me I have a 140w soldering gun you could have used.

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But that would have been too easy now, wouldn’t it have been? Haha

Duly noted. Can I borrow three eggs?

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Lol ya probably would have been too easy, who wants easy anyways.

Lol 3 eggs sure no problem. I can have my wife get them out for you, just let me know so I can tell her. Just a heads up they take longer to cook on the heat bed then on the stove.

Hahahahaha…I might have just spit tea all over the place…

It’s really amazing how many people don’t use those holes at the back of the plate to mount the wires… :slight_smile:

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