Fire proof enclosure? (Page 1 of 2)

You would likely need to contain the spool of filament within the enclosure as well.  Otherwise, if the filament catches fire inside the printer its just going to travel right outside the box.

I think an easy option would just be rigging up an automatic fire extinguisher inside the case. Although you probably still need a way to interrupt the power in the event of a fire.

I would second Elmoret's suggestion of keeping a fire extinguisher and smoke detector near the printer and also have one outside the door of the printer room, this is how I have my metal casting room set up since I am continuously dealing with temps from 600F to over 1800F it just common sense to have several means of dealing with fire at quick and handy locations to access because with fire you don't have much time to play with it... you either get it out in the first minute or it's toast.

Here's a crazy idea:  how about filling the enclosure with an inert gas, so even if temperatures got out of hand a fire couldn't propagate?

I'm picturing a sealed dome (box with open button) enclosure that drops down over the entire printer and spool.  You could then fill it with helium if you needed to print a long print, or hook up a small tank (or a large balloon) some sort of heat sensitive valve so that if the a fire did start inside the compartment, it would fill with gas that would snuff it out.

Although, I guess at that point it would probably be easier to just put an automatic halon fire extinguisher next to the printer:

http://www.ebay.com/itm/Halon-SS-30-Fir … 4897.l4275

I think that's what I'm going to do.

Dunndunndunnnnn dun dun dun....

Thanks for that link, Teal.
Should ease my paranoia significantly.

This is a crowd funding thing that I'm running: http://www.gofundme.com/bvi140 It's for pretty selfish reasons

There are more sources of fire than just inside the build area. I have smoked an electronics board once. And I have heard of others having power supply failures. If your going to build an anti-fire system, then you should contain the entire machine with spool.

In Skyminer's topic it was discussed one of the potential cause of catastrophic failure could be extruder temperature going to the roof, or electric short that ignited the plastic.
How can this happen and how to avoid this proactively?
1- complete controller freeze. the extruder (and bed) temperature are actively controlled by the firmware, if firmware locks up the extruder mosfet could be left permanently on.
Solution: passive hardware solution like a thermal fuse that breaks power if temperature reaches an abormal temperature.
I found these inexpensive and small devices that could be bolted on the extruder or its proximity.
http://www.thermodisc.com/en-US/Product … lletin.pdf
http://www.atcsemitec.co.uk/pdfdocs/PEP … l_fuse.pdf

Any suggestion on how to implement them? Should it break just extruder power or printer power? I don't think it would be a good idea to run AC wires along with other extruder wires. A relay connected to power supply?

2- thermistor dislodgement and/or inaccurate reading. If thermistor is shorted it would trigger max_temp. If disconnected it would trigger min_temp. But if it is simply dislodged and stays near the extruder? or if it is producing a false reading? Is this possible?
Possible solutions: additional thermistor? thermal fuse? firmware protection (maybe in the PID routine)? A combination of all three?

3- Electrical short circuit: in this example extruder wires got tangled into the extruder. Could it ever happen to the Solidoodle?
http://forums.reprap.org/read.php?1,294850,page=1
Anyway the controller could fail for any reason and it is not protected at all.
Solution: metal box for controller? Fuse? Keep filament spool far from the electronics? Default setup is very close.

4- Power supply failure: if positioned directly underneath filament spool it could ignite it. But where to locate it?
Solution: switch to an all-metal quality desktop computer PSU?

5- stepper motor failure: if stepper motor stops working (jam, belt failure, driver failure) I suppose the printer will keep going. If extruder jams and sits on the printer part could it be ignited?

I don't think smoke detectors are useful except to ring an alarm. As said if there is smoke there is already a fire. Automatic Fire extinguisher for engine bays would be clever as they don't depend on electrical devices.

Any other thoughts?

You're right Elmoret, all thermal cut offs I've found sustains 200°C continuous use, I wonder if there is a technical limitation of the pellet substance or just lack of demand. I might write to the manufacturers to understand.

Could it be placed near the extruder where normal operating temperature is right below 200°C?

As you have definitely more experience with the hardware involved compared to me, will an always-on extruder reach flash point and/or auto-ignition temperature of ABS, which are 390-420°C the former and 460-510°C the latter?
What about limiting maxium extruder power? This will lengthen warm-up time but it is an acceptable trade-off.

You're right, MOSFET could fail. Here's an interesting document http://www.4qd.co.uk/serv/MOSFETfail.html
But what can cause an hazard from a MOSFET failure? The exploding MOSFET itself? In this case a metal enclosure for the controller itself should be enough. And if shorted the thermal cut off will take care of shutting down the printer.

If we use a relay to shut down printer we have to consider also relay failure. But I think we should concentrate on the hazard with the highest chance of occurrence.

you can use this.. put the head jut above your printer... automatic extinguisher

http://www.amazon.com/Fire-Fight-Produc … tinguisher

or this :

http://www.amazon.com/Fire-Fight-Produc … tinguisher

or even this :

http://www.amazon.com/BLAZECUT-Automati … tinguisher

that you can put just around your printer or above..

all are set of eletrical and common fire. (A,B,C)

and this one that is a lot cheaper:

http://www.amazon.com/Sun-Systems-Flame … tinguisher

edit : i removed the picture and join it to the message because they are too big

IMHO, an environment with an inert (or relatively inert) gas (like nitrogen or helium) would be far easier to maintain and less likely to adversely affect the heating and cooling behavior of your printer.  I imagine the main board, extruder, and motors would all fry very quickly without any air or gas to cool them or create the necessary thermal gradients for proper operation.  On the good side, however, a heated bed would finally heat up quickly!

Don't suppose you've got a link to the supplier this magical material?

This is a crowd funding thing that I'm running: http://www.gofundme.com/bvi140 It's for pretty selfish reasons

^ Clear / transparent Polycarbonate can be found on McMaster.. Also they'll sell it at the following:

professionalplastics (.com)
tapplastics (.com)
portplastics (.com)

A lot of polymers are flame retardant and self extinguishing.. Many will be UL 94 V0 compatible, which is the way to go.