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3D Printer Fire protection

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paulca:
Hi,

tldr; could I use an IR sensor and smoke sensor to provide a "last man standing" fail safe against unattended 3D Printer fires?

So it turns out the 3D printer I bought does not have "thermal runaway" protection or the manufacturer disabled it in the firmware.  This isn't a big deal I can reflash with firmware that enables it.

3D printer thermal run away occurs when the "hot end" heater for the nozzle and it's thermistor become detached somehow.  Either the heater or thermistor falls out.  The software see the temperature is low so it powers the heater and eventually the heater becomes hot enough to ignite plastic parts, tape or wire insulation etc.  You have a fire.

The same can occur with the heated bed heater, possibly.

The only 100% solution is to never leave the printer unattended.  However it is not uncommon to find larger prints which can take well more than 16 hours to print, so either you need a buddy and take printer sitting in shifts or you have to leave it unattended at some point to sleep.

The solutions for thermal runaway and ensuring the PSU is sane as well as looking for tear down reviews by experienced electronics folks confirming the electronics are rated for the amps they will be pulling etc.... are all very well, but there can be causes of fire which are simply component failures.

First I intend to update the firmware to include said thermal runaway protection.  I also intend to move the printer to the garage, this is more due to the noise of the thing.  The printer will then be monitored by web cam remotely.  If it did go on fire in my garage, as it's just concrete floors, bare stone walls it would need to get pretty intense to get to the next combustible thing, the bare 2x4" wooden roof beams.

However I was considering mounting either (or both) an IR heat detector and smoke detector directly above the printer which would, if hitting thresholds pull all power to the printer.

I know IR detectors exist for kitchen flame detectors and I'm sure hunting for one that would trigger at a temperature of say, 350*C (well higher than the operating temp, but below the ignition temp of plastics) is plausible.  I also know you can get RF 433Mhz smoke alarms, from which you could remove the sounder (or just leave it) and trigger the shutdown off the RF signal. 

Plausible?  Worth doing?

bd139:
Mine is arriving tomorrow and I worry about this. I am going to not leave it unattended. I can squeeze some prints in during the day fine and long ones can wait until the weekend

Siwastaja:
Classical single-time-blow thermal cutoff device (thermal fuse) in series. Very commonly used in all thermostat-controlled heaters, because the problem isn't new at all. It's beyond me why it's not employed by default, it's a total no-brainer.

https://www.digikey.com/products/en/circuit-protection/thermal-cutoffs-thermal-fuses/146

Of course, it needs to be mounted properly to the heater element. No iffy kludges.

Monkeh:

--- Quote from: Siwastaja on September 30, 2019, 01:21:18 pm ---Classical single-time-blow thermal cutoff device (thermal fuse) in series. Very commonly used in all thermostat-controlled heaters, because the problem isn't new at all. It's beyond me why it's not employed by default, it's a total no-brainer.

https://www.digikey.com/products/en/circuit-protection/thermal-cutoffs-thermal-fuses/146

Of course, it needs to be mounted properly to the heater element. No iffy kludges.

--- End quote ---

The highest rated holding temperature there is 220C. I regularly print at 235C - irregularly at 260C. So, brainer required.

Siwastaja:

--- Quote from: Monkeh on September 30, 2019, 01:30:53 pm ---
--- Quote from: Siwastaja on September 30, 2019, 01:21:18 pm ---Classical single-time-blow thermal cutoff device (thermal fuse) in series. Very commonly used in all thermostat-controlled heaters, because the problem isn't new at all. It's beyond me why it's not employed by default, it's a total no-brainer.

https://www.digikey.com/products/en/circuit-protection/thermal-cutoffs-thermal-fuses/146

Of course, it needs to be mounted properly to the heater element. No iffy kludges.

--- End quote ---

The highest rated holding temperature there is 220C. I regularly print at 235C - irregularly at 260C. So, brainer required.

--- End quote ---

You just need to look somewhere else. The world is literally full of thermostat controlled systems at that temperature range, and many certainly do have thermal fuses for safety. They must exist.

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