Beware your 3D printer (They can cause fires) (Page 6 of 8)

Soldering is the right answer here.

didn't know it had a special name, but after googling 'western union splice', that is exactly the type of splice I have used for years (both with and without solder)

When I splice a pair of wires like that, each wire is soldered, then heat shrink put over, then another heat shrink over the pair  as well.  It's cleans it up an adds strength to the splice.

That kind of fire would burn out to quick and not be of a sufficient temperature to ignite anything in the printer itself. The vapors burn off with in seconds and worse it might do is blow your enclosure door open.

The reason hairspray is "flamable" is the aerosol that propels it. This evaporates almost immediately, so unless you're spraying hairspray across an already burning fire, hairspray won't cause fires nor will it accelerate a fire that starts later on. Hairspray is only dangerous while it is being sprayed; dried hairspray is not dangerous.

- Firefighter

What if the E3D cooling fan shuts off; will enough heat go up the cooling fins to melt the PLA mount?

I have all fans powered via a separate power supply. Like a numskull, yesterday I began a print without turning the fans on.
The printed fan shroud warped to the point of falling off and flopping around mid print. It caused a solid clog which caused the Hobb Goblin to completely chew through the filament, severing it just about the PTFE. The extruder warped enough to change from a tight fit to a wobbling mess.
That all happened in the 5 minutes I went out for a smoke.

Unless you use high temp PLA you do not want to use any mechanical parts in PLA. My ABS parts warped after 5 minutes, so image PLA in that time. No bueno.

Reiterating that thermal fuses aren't really available in high enough temperatures to be useful on an extruder (240C is the max rating
I've found, and this is approximately what most people print ABS at - you'd want something a bit higher ideally!).

Indirect methods you should probably test at least once - e.g. a lower-rated thermal fuse on the heatsink. You'd have to be confident that in a typical over-heat scenario this fuse did actually trip before the nozzle started to smoke...

Az could fix his error by interlocking his fan power and heater power - probably the easiest way to do that would be to have them on the same supply.

Most of the fire danger depends on the printers construction. The newer mostly metal printers will present very little fire danger and I would have no worries about running my CTC all metal Dual over night or while at work. These printers that have a lot of plastic in their construction are going to be the one to worry about.

On modern PCB's the parts are all made to self extinguish so the chance of the controller being a fire source is very low. The heaters as long as they are mounted to/on metal surfaces should not pose much of a fire risk either. Honestly unless you just own a Frankenprinter that is built of plastic and/or wood and has wires all over the place  I would not be really concerned. I have been printing for over 8 years and have owned 6 different printers.

I have had 24 hour prints run on all of them and never had an issue. I am just going to keep taking my chances and trust in the construction of my current units Which are nearly 75+% all metal. And 100% metal in all the areas a fire could be generated.

I am not saying a fire is not possible but I feel it is about as possible with a modern printer as it is with a computer or TV or other electric/electronic appliance.

This is a design issue and hotend designers should consider this. My hotends on my CTC use thermocouples. Those are actually bolted to the side of the hotend and the wires are jacketed in a stainless steel braid. They will not get pulled out or off by any force that the steppers could put on them. As for thermistor based systems why is the thermistor not mounted from the top of the hotend?

I feel most if not all of these printer fires can be attributed to one or both of two things. Rushed mods and poor wire handling.

Rushed mods include such things as upgraded beds that exceed the capacity of the switching MOSFETS. Upgraded hotends that again maybe not knowing went from a 25 to 40 watt heater and again exceeding the MOSFETS capacity.

Poor wire handling can include bad or unprotected splices, poor crimps, loose connections, poor routing and so on.

I would be really curious to see or know if anyone has had a fire that actually started a flame on an all stock machine.

I am not downplaying the importance of safety here but I also don't feel there is a need for extreme paranoia about a fire in your machine either.

As long as you take the time to research the parts and make sure they are within your hardware capability, you take the time crimp the wires properly, use crimp type splices or solder splices and cover them with shrink tubing or actual electrical tape and you make sure all your connections are secure and use proper terminals I see a printer as being just as safe as a clothes dryer, or space heater.

Now for added safety, I don't see why nobody has written code at the firmware level that will monitor temp and stepper activity. If the temp drops or rises by more than 50 degrees while the steppers are running then it will shut down the heaters. If the motors stop for more than say 30 seconds while the machine is at set temp it shuts down power. Yes I know there is the danger of a stuck MOSFET but if you have a logic controller relay on your mains then that takes care of that. Just use a mechanical latching relay that requires a person to reset it for normal operation.

I myself will take my chances. As I said you have circuit boards all over your house now so the chance of a circuit board fire is all around you now and there is a lot of stuff that is running on standby mode or on an automatic system that always has power on it.

As for the heater cart getting hot enough to melt Aluminum I would need to see some proof on that. I am pretty sure the connections to the heater cartridge would fail long before it got that hot but I may be wrong. Also you don't have to have aluminum in your hot end. The B3 Pico is solid stainless steel. My CTC (now FlashForge copy) uses steel for the block as well. Again though I seriously doubt it could get hot enough to melt the heater block before the heater itself failed or opened.

Well like I said, just another reason not to use aluminum. Your printer is only as strong as it's weakest component.

There is a reason why they stopped using aluminum in home wiring.

And just so we're 100% clear here... on how much your hotend CAN melt...