Hey all, just read a post about a fire from a hotend mishap. Here is a mini detector with a built in relay. Everyone should check this or something similar for safety sake.
[www.aliexpress.com]

I too have just had a fire on my Prusa i3 and ordered the same unit from ebay!
Thinking of adding an SSD to kill the 12 lines in a fire but working out the battery backup is literally giving me a headache (or its the alcohol i'm drinking!)

[henrysbench.capnfatz.com]

Edited 1 time(s). Last edit at 07/18/2015 02:47PM by GRAYWOLF.

I saw that too. Would a thermal fuse on the power for the heated bed and hot end be just as good?

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Newbie with Folgertech 2020 i3.

I'll be interested in hearing whether the smoke from the normal operation of the hot-end triggers that thing.

I'm still trying to figure out how you'd use it to kill power to the printer.

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msaeger
I saw that too. Would a thermal fuse on the power for the heated bed and hot end be just as good?

I use firmware and hardware watchdogs to prevent the hot end overheating, and I have smoke alarms in the rooms where the printers are. I never leave the house when the printers are on. However, IMO a thermal fuse on the hot end would be good, if you can find one small enough. For the heated bed, it should be possible to choose the right power so that it doesn't get dangerously hot even when left running at full power.

Edited 2 time(s). Last edit at 07/19/2015 01:22PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

As I mentioned in another thread, I have installed a smoke detector that cuts the power to the printer. It has been in use for about a year. It is based on an Aico Ei141 ionisation type smoke alarm with an integral Ei128R base unit that houses a switching relay. Other manufacturers should make them with an integral relay. Because it is momentary contact, an external latching relay is required for the circuitry and I housed this in a separate box. I have looked for a thermal fuse but can't find one suitable.

I don't leave the house when I am doing a print or print overnight. Instead I have tried to get the speed up on my printer to shorten the print times as much as possible.

I also like the idea of a webcam. You can view the print from an android phone if you are in a different part of the house.

I also invested in a large CO2 extinguisher, if all else fails.

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dave3d
As I mentioned in another thread, I have installed a smoke detector that cuts the power to the printer. It has been in use for about a year. It is based on an Aico Ei141 ionisation type smoke alarm with an integral Ei128R base unit that houses a switching relay. Other manufacturers should make them with an integral relay. Because it is momentary contact, an external latching relay is required for the circuitry and I housed this in a separate box. I have looked for a thermal fuse but can't find one suitable.

I don't leave the house when I am doing a print or print overnight. Instead I have tried to get the speed up on my printer to shorten the print times as much as possible.

I also like the idea of a webcam. You can view the print from an android phone if you are in a different part of the house.

I also invested in a large CO2 extinguisher, if all else fails.

I'm quite surprised that you don't get false alarms with the ionisation device and foreign body's on the hotend getting burned off can trigger them.

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Graywolf wrote:
I'm quite surprised that you don't get false alarms with the ionisation device and foreign body's on the hotend getting burned off can trigger them.

I have got the detector head on top of a bookcase immediately behind my printer. I have just measured the distance and it is about 70 cm away from the hotend. I don't get any false alarms with normal printing. I have tested it with a lighted match but it hasn't been used in anger yet.
What prompted me to install it was an incident when I first started that filled my living room with smoke. A print became detached and it dragged the thermocouple out. A ball of molten plastic was being dragged round and round with the hotend temp going out of sight. No flames but thick smoke. I am sure such an incident again would trip the power early on.

Isn't there a line of code that can set limits on hotend and heatbed temps? 20% over limit cut power?

That only works if the thermistor is in place and intact, and is already present - it's the MAXTEMP limit in Marlin. If the thermistor falls out, there is another line of protection that is supposed to engage after things hit temp, that if it can't hold temp (or thinks it can't - IE thermistor is now reading room air) that it will cut power . . . . but even that won't help if a MOSFET fails.

- Tim

Edited 1 time(s). Last edit at 07/20/2015 07:10PM by tadawson.

I switched from Marlin to Repetier firmware. It is much better and easier to configure using the online web page.

[www.repetier.com]

There are a lot more safety features. There are settings to catch a thermistor being upcoupled using min temp rise for example.