Can I save a print from "Bed Thermal Runaway"?  

Re: Can I save a print from "Bed Thermal Runaway"?

Hi Ben,

does the display show what Z height the problem occurred at?

if it does, make a note of the height,

if the model is still bonded to the build plate, you can
a, consider editing the gcode to delete the gcode that has been completed and try continueing from there (Assuming that the printer still works.)
b , cut the model at that height in Slic3r, print the remainder, and glue the parts together afterwards

regards Joan

Re: Can I save a print from "Bed Thermal Runaway"?

the big question, is what caused the Thermal runaway...

the thermister may have come adrift...

(never had that happen to me)

the connectors may have come adrift, and or melted... (again never happened to me)

the output mosfet may have gone faulty (Nope, never happened to me)

it could be that the cabling is failing with constant flexing...

this has happened to me, a number of times....
Once on my Mk1 printer (Mk2a Heatbed)
Once on my Mk2 Printer (Mk42 heatbed)
Once on My Mk3 Printer (Mk52 Heatbed)

Each time I replaced the cable with Flexible Silicone insulated wires,

The original Prusa cable had about 27 conductors / strands of copper \
the replacement had about 250 Conductors / strands of copper wire of a much finer gauge making it inherently much more flexible.

when I upgraded the Mk2, to mk2.3 (not the full mk2.5) I put silicone flexible cable on from day one, to reduce the chances of breakage

regards Joan

Re: Can I save a print from "Bed Thermal Runaway"?

Joan,
I ran into this flex fatigue failure problem with the efector whip on my delta about 4 years ago and I too went with the same Silicone high flex wires.... On reflection I should have done the smart thing and replaced all wiring subject to flex with the same stuff as I built my kit. It is available from 8 awg to 28 awg and I have a stock of it on hand from 14 awg to 24 awg. The call of the all the nice wiring all pre made up with connectors was too much for me and it pushed the memory of those flex fatigue failures into the dim past it was left forgotten in the rush to finish my new toy tool.

Given those 300+ printers beavering away in Prusa's printer farm 24-7 one must assume either he is also seeing these flex fatigue failures or he is proactively building his farm printers with high flex wiring. Either way he knows about it and yet he is not including this wiring into new production. Why?

I think it is that market research has shown that the vast majority of printer users print less than a kilo a month and so are unlikely to see this flex fatigue failure in the lifetime of their printer. Enthusiasts as seen here in these forums and on youtube and the facebook groups make up such a small percentage of the total user group (and that they tend to rebuild and upgrade their printers as a major part of the enjoyment the get from the hobby) that they will just incorporate things like high flex wiring into one of their upgrade rebuilds all on their own expense.

Re: Can I save a print from "Bed Thermal Runaway"?

Joan, thank you for your thorough responses.

The positive wire on the rear of the heatbed broke; it would seem that the strain relief wasn't very relieving. And after re-soldering the wires (I stripped and re-did the ground as well as it appeared somewhat weakened as well) and buttoning everything back up, I wouldn't be very surprised if it were to happen again.

As for rescuing the print, the Z height was displayed, but I'm unsure if that was the last height it was extruding at, or the position it took after retracting. We shall soon see...