Agreed w/ @Lukas_Mathis … cheap Chinese junk running lots of amps through non-flex-rated flex wiring without any software safeties is a hazard to life and limb.
I bought a Prusa i3 MK2S as my first printer. The thermal runaway feature was a must have for me. Now im looking into assembling the hypercube evolution but im scared because i dont want it to fail at catching a thermal runaway failure lol
check the connection at the bed. i got a short there. easy to fix
@Stephanie_A you are of course, correct, about bed maxtemp; my bad, including not emphasizing the overall fire hazard. Bed, head, doesn’t matter; any fire can leave you dead. I’m a paramedic, been on calls where people died in fires.
Relying on firmware only tests is false security. Failed on MOSFETS, shorted supply wiring, bed, hotend, even a seriously overheating stepper, it really won’t matter if you’ve got MAX/MIN/Runaway temperature sensing if the firmware can’t shut off the power. Thermal fuses, like those in coffee pots, or fused DC are very rare in 3D printers. Has your printer passed UL or CSA testing? What would your insurance company say if it burned down your house? Not covered? You never want to be in a situation where one catches fire and you don’t notice. Worse, be asleep in a burning building.
If you’re going to leave a print going overnight you need to think about what’ll happen if something starts on fire. What’s around it? What if it falls off on the floor? Where will the smoke go, it’s potentially just as bad as the flames. Will you hear the smoke detector, and would you trust it with your life? Where’s the nearest fire extinguisher? I’ve left my printer running and watched TV or had dinner in a different room, but the thought of sleeping while it’s going is scary.
Sorry to be soapboxy. Fires bring up bad memories.
An experience I had years ago was I started my 3d printer and then went to take a nap. I woke up to the smell of fire. I run over and look at my printer, whose frame is wood, and see one side of it on fire.
The connector for the bed was underrated. It melted and got red hot. Eventually it caught fire and melted the already hot wires, which were also underrated. This caught the frame on fire. I was lucky that I was still home and that I woke up. A couple of minutes later and I might not be alive to warn others.
You are right that firmware alone isn’t enough. A mosfet can be stuck in an “on” state, which can only be corrected by removing power. A thermistor can fall or detach. So many things can go wrong.
Was that a Printrbot?
What you need is a thermistor fuse like the one found on a clothes iron. When goes above a certain temp is goes open circuit. You are in no danger right now. Continue the print but insulate the bare wire. I am building a DBOT have been ordering and waiting for parts since Feb. Last of it arriving next week hopefully. I will post pics of the heating safety hardware.
@JERRY_NAIDOO when it goes open circuit is it permanent or temporary?