“Good judgement comes from experience, and experience comes from poor judgement.” – Rita Mae Brown
I’ve been 3D Printing now for a couple of years. I’ve burned out control boards, hot ends, connectors on heating elements like the rest of us. But the other day something happened at around 3am on a Friday while I was up late working on a 3D model and printing some parts in my workshop downstairs.
My Anet A8 caught fire.
I don’t mean it got hot, or there was a little bit of a flame… it was engulfed:
This is a photo of one of my two ANET A8 3D printers shortly after I walked into my workshop smelling plastic to discover the entire left side of the frame engulfed in flames. Thankfully I was wise enough to install a fire extinguisher in my workshop and was able to put out the fire before it got out of hand — but it is terrifying to think of what could have happened if I wasn’t home or sound asleep.
With the fire out and everyone and everything under control the first question I asked was “How the hell did this happen?!” I’m sure if you’ve been 3D printing for any length of time you’ve heard the horror stories about cheap chinese parts, and trust me I’ve had more than one bad connector get hot and become a fire hazard. But how this fire started was different and there are a lot of lessons to be learned from it for my fellow 3D printing friends worldwide.
The Evidence: How my Printer Caught Fire
Before I explain how my printer caught fire, let me explain how this printer was configured and the upgrades it had at the time of the fire:
- Upgraded Hot bed using a 110V silicon heating source and a 10A Solid state relay to turn it on and off (I used the original thermistor still to measure temp of the hot bed)
- A thermal-conductive silicone on top of the hot bed and a piece of glass on top of that
- An X-axis chain carriage to keep the wires on the extruder from straining unnecessarily
- A standard ANET 1.0 control board running the default firmware
- A full-circle cooling fan for the hot end 3D printed in ABS
- An upgraded cooling fan that moved more air
- An upgraded thermistor for the hot end that screwed into the block rather than being held in place with a screw
- An upgraded 30A power supply
Everything else was standard. So I’m sure there are going to be those who read that list and immediately are going to want to chime in and tell me which particular upgrade (or lack thereof) is what caused this incident. Chances are though all of those theories are probably wrong!
What happened to my printer was caused by a combination of events that I think should give anyone who owns a 3D printer a moment’s pause. In my case a lot of the things that are commonplace considered “upgrades” and “safety related” nearly burned my house down.
Where the Fire Started
It took me awhile to figure out where the fire started. Once the printer was cool enough to handle (or what was left of it), I started looking around to try to figure out what caught fire.
Was it the power supply?
Faulty cheap power supplies are always a good guess when one things of how a fire might start. But nope, wasn’t the power supply! The entire right side of the printer where the supply was had no damage to it at all.
Was it the control board?
In the world of 3D printing it is a well-known fact most vendors of open source hardware like this use cheap components that are not rated for the job they are to do. This generally happens at the connections, where a little bit a resistance and a lot of current causes the plastic connector to heat up, melt, and eventually can start a fire.
But that’s not what happened here either. It’s a little hard to see from this photo but the high-power connections of my control board actually didn’t get damaged. In fact it looks like the control board was damaged by the fire, it didn’t cause the fire:
Was it the Hot bed?
I did have a serious hot bed installed on this printer, a 110V 200W silicone mat attached to the bottom of the aluminum bed is certainly a suspect. But when I examined the bed, other than the damage done by melted plastic and the fire the silicone mat itself was still in perfect condition, as was the wiring for it.
How did the fire start then?
If it wasn’t the power supply, control board or heated bed then that really leaves only one option: The hot end. Check this photo out, taken as a profile picture of the printer looking from the left Z-axis to the right:
This gave me my first real clue as to what produced enough juice to start a fire — look at the heat element just dangling there by itself! It should be securely inside of the hot end block but it’s completely free. It seems that this is the likely source of the fire. It would seem that the heating element managed to shake itself loose without me noticing. That was the “triggering” event that set off a whole chain of sorry. I normally run Marlin on my ANet but I had also recently replaced my control board, so at the time the fire occurred I was still using the stock firmware which does NOT have thermal runaway protection (which is when the firmware automatically shuts the whole system down if it detects strange temperature readings like when the hot-end falls out).
Okay, so we know where it likely ignited, but how did the fire spread to the point where it caught the entire frame?
That’s where things get interesting.
How the Fire spread
I print a lot, like most people, with PLA. Because of this I was sure to upgrade my printed with a full-circle fan duct that completely surrounded my hot end. Of course I printed this in ABS so it wouldn’t melt. But ABS certainly can melt and catch fire, especially when you put enough heat on it.
So when the heating element for the hot-end came loose, I suspect what happened is it managed to get itself wedged between the block and the fan duct and that’s where the fire actually started by igniting the ABS.
Once the Fan duct caught, it was in a perfect location to spread as it climbed up the fan duct, ignited the other ABS parts I had printed for the filament cooling fan, and I suspect eventually completely engulfed the extruder. As it burned chances are pretty high the extruder itself stopped moving (as you can see from the photo it died in the middle of the bed) — so how did it spread to the entire left side of the frame and nearly burn my house down?
Remember the X-axis chain I had installed, in large part to keep the wiring to the extruder from moving around and starting a fire? Well turns out when you have an ignited pile of ABS directly below the chain it doesn’t take much for it to catch fire as well — which is exactly what it did. If you look at the photo from the fire you’ll notice on the right side what’s left of my yellow-and-black x-axis chain.
This chain basically acted like the worst 3D printed fuse for lighting your house on fire, and the fire used it to travel across to the left side of the printer. It eventually made it to the mounts where it attached to the frame on the left side and caught fire to the mount for the X-axis stepper motor. As it burned it dripped fire-plastic on to the frame, and eventually set the entire acrylic on that side on fire.
It’s about at this point I smelled something and walked into my workshop to discover a 3-alarm fire.
Lessons learned
There is a LOT to learn from my unfortunate experience nearly burning my house down, and I strongly encourage all of you to take heed to my advice because any one of these things maybe wouldn’t have stopped the fire (there really was one thing that could have done that), but it was a combination of these things together that caused this accident.
Smoke Detectors / Early Warning Systems
This really should be more obvious than it was for me. Install a smoke detector, directly above your 3d printer setup. Stop reading this blog post, click here, and order one for your printer – right now.
Secure your hot end, and then secure it again
This fire would never have happened if the heating element of the hot-end hadn’t managed to get loose. On an ANET A8 the hot end slips into the block, which you then squeeze to lock in place using a screw you tighten in the block. I’m very much not a fan of this design, and would rather see a heating element you could screw into the block so it can’t come out. I haven’t found that design (yet), but there are a few things you can do to make a real impact on preventing the problem I had before it started:
- Make sure the heat element is secure, often: Check it every print, or at least try to remember to if you don’t want to burn your house down.
- Wrap your hot-end with heat-tolerate material: This is typically a suggestion for people who are having trouble keeping their hot-end at a certain temperature to insulate it. It’s great for that, but if I had wrapped my hot end I might have had an added layer of protection from it slipping out.
Don’t use fan ducts that are certain to catch your hot end and ignite it if it comes loose
When you get a stock ANet A8 it comes with a silly little fan duct that seems like it won’t do much to cool your prints. That’s true, but if I had had that fan duct instead of my upgrade I probably wouldn’t have almost burned my house down (the hot end would have flopped around but I doubt it would have stayed in one place long enough to ignite anything). I’m going to go for half-circle fan ducts that still provide decent coverage (and use an upgraded blower fan), rather than a fully enclosing one for exactly this reason.
For that matter, just be careful in general with how much plastic you put on your extruder in general. One thing I’ve realized from this experience is this: While it’s great to 3d print upgrades to your extruder, you’re basically adding a bunch of plastic-fuel right next to a heat source and to some degree just begging for it to catch fire. Be careful, and try to think about what would happen to your extruder rig if the very bottom was to ignite.
Do not print using the default firmware
The stock Anet A8 firmware (I’m honestly not even sure what it ships with) is the digital version of a loaded gun when it comes to fire safety. Probably in an effort to make the printer more forgiving to beginners, the stock ANet A8 doesn’t seem to have any thermal runaway protection at all and will keep right on printing even if the temperature readings don’t make sense! If I had been running Marlin, perhaps the printer would have noticed it kept trying to get the hot-end to temperature but the temperature wasn’t responding appropriately and halted before anything got hot enough to ignite.
Have a fire extinguisher within arms reach of the printer
I saved my workshop, if not the entire house, by having at fully charged fire extinguisher next to the printer setup. Click here, buy it, install it near by as soon as it arrives.
Be wary of carriage chains
I’m not going to tell you not to install a carriage chain, because they are really great cable organization tools for your printer. However as you can see from what happened to me, they also add a lot of plastic to your printer just waiting to be the world’s worst fuse to burning down your house. Since one of the points of good cable management is to prevent strain on wires and consequently possibly prevent an electrical fire, this one is sort of a catch-22 situation. I’ll probably still use them, opting to do everything in my power to keep the integrity of the hot-end in-tact instead.
Rethink your workspace
This whole experience has also made me question how I set up my workspace. Like so many others, I installed my 3D printers in furniture from Ikea — in my case a large wardrobe with nice slide-out shelves to house my two ANet printers. But after seeing what a 3D printer fire can look like I realize I basically put the printer inside of a burn-my-house-down box. I know when you are printing in ABS everyone wants a nice enclosed printer, but either do it in plastic or use a silicon mat to get your heated bed up to temp. It’s not worth the risk of burning your house down to prevent some ABS curling.
So what’s next?
Well, I guess I’m going to have to get a new printer of course. I’ll start by digging through the carnage and seeing what, if anything, I might be able to salvage. Since the fire was really limited to the left side of the printer I should be able to save my solid state relay, and maybe even my 110V silicone heating pad. The PSU is also probably in good working order still (I’ll run it through its paces on my workbench). Two of the four stepper motors are probably 100% fine, as is of course the LCD screen itself.
In the meantime I still have another ANet A8 that I’ll be immediately checking the hot-end of (and replacing the full-circle fan duct of) while I wait for a replacement.
Safe and fun 3D printing to everyone my friends. I’d love to hear your thoughts and comments on how you make your printer and yourself safe from the sort of disaster I only narrowly avoided. Finally, enjoy the collection of the wreckage below!
Great info,
Bought a fire extinguisher and smoke detector after reading it.
Didn’t know about the fire extinguisher balls! definitely interested in one as well.
Did a quick check looking for the must-have and should have write-up but couldn’t find it. Is still in process?
Again, thanks for the great info.
Fredy
Any idea how the hotend cable managed to jump over the top of the carriage and rods, it should have been on the other side! Was it fastened to anything?
Hello all,
Great article, shame you had reason to write it though. What shook me was how rapidly it appears to have taken off. Without knowing the facts, I would have assumed from the pics that the fire had been burning for 30 minutes at least. But I do know how even a small fan can make a fire escalate in seconds.
I’d like to offer the lesson I learned from my printer to the discussion:
With any mains or lithium powered appliance in the home, I suggest you should think in terms of when, not if. I.e. I assumed from the first moment I powered my printer, that IT WILL overheat at some point in time and possibly cause a fire. I then asked myself what can I do to prevent disaster ‘when’ it happens?
The ‘when’ attitude created a sense of urgency and thoroughness. Rather than simply focusing on prevention (like I used to), it forced me to consider things like locating the printer so ‘when it ignites’, it doesn’t block exit paths. I also mounted two small flashlights near both exits, with a spare door key attached, and mounted another flashlight next to my bed; neither of which I’d ever considered before.
Even though I always considered myself a safety conscious, thanks to owning a 3D printer, and adopting the ‘when’ not ‘if’ approach, I have a proper emergency plan now. I go to sleep knowing that if I were to wake with flames at the bedroom door, I know exactly what to grab to smash the window out with, and next to it is always a blanket, regardless of the season.
Some of you may see this as paranoid, but it’s exactly the opposite, I’m less concerned now than I used to be, because I’m more prepared! The $300 spent on my printer was the best ‘safety investment’ I’ve ever made (other than smoke detectors), so the printer paid for itself in a way.
I suspect if you sit at your printer now and ask yourself “What will I do ‘when’ this erupts, and how can I lessen the damage?”, within a few minutes you will probably have six simple and inexpensive ideas which might save you or your family one day.
Happy printing, and sleep well 🙂
Paul
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Good post.
Necessary for whoever is planning to buy some cheap anet a8.
It’s all unicorn and magic to print under 185 USD but it’s way harder to realise the risk you are taking if you don’t understand safety measures.
I would print that and send it with the anet a8 if I was the manufacturer.
I have seen, while working on my printer, how hot the heating element goes when the thermistor or the heating element goes loose. It will melt everything. The wires of the heating block, any PLA close and even kapton tape that is on it.
-I highly suggest to change the stock heating block for something that has a screw to fix the thermistor and a screw to (not like the stock anet a8 one) fix the heating element inside of the heating block.
https://www.tdegypt.com/wp-content/uploads/2016/11/Brand-New-Best-Quality-1-Piece-Aluminium-font-b-Heat-b-font-font-b-Block-b.jpg
I agree on the block for sure. I’m actually writing up a post on all of the safety improvements I’ll be doing to ANets in the future and that new block is certainly one of them (I go a step further, and actually add a little bit of thermal-conductive glue to the end that can be chipped off if you really end up needing to replace the hot-end)
Very interesting post, indeed! Thank you Jay for sharing it.
To the many who commented, I’d say that speculating about the actual cause of the fire is probably not essential.
The important message of Jay’s story is: your printer CAN catch on fire, and can do it BADLY.
So… take proper precautions to prevent it, and those to minimize the damage in case it happens, anyway.
To this respect, I believe that we all should treasure Jay’s excellent list of lessons learnt, and adapt it to our personal situation.
I have only a few additional comments (just some food for thought, with no pretense):
– Smoke detectors: better have two of them, at adequate distance. Be sure that they are close/loud enough to wake you up, should you be sound asleep. But also think: what if you are not at home? I wouldn’t recommend printing if nobody is at home.
– Take care of your hot end, regardless of whether that was the cause of Jay’s fire
– Have a fire extinguisher: rather than within arms reach of the printer, I’d put it 6-10 feet apart from the printer, towards the room/workshop main entrance, so you don’t risk that the extinguisher is unreachable in case the printer catches on fire while you are away
– Be wary of carriage chains: I use Flame Retardant PET Expandable Braided Sleeving for keeping my cables organized. They are great! The only drawback… you need a bit of practice to install them. (So, if you do not have experience, but some extra)
– Rethink your workspace: that is crucial! Also think of what you have around your printer, in terms of tools and potentially inflammable objects or substances. For instance, I often use rubbing alcol for cleaning the hotbed, but I put it on a desk that I have behind me, when I am sitting before my printer, and I store it in a cabinet when I leave the room.
Also: I built a printer enclosure, which sides are made by fire-resistant dray-wall panels. The idea is to keep the fire confined as long as possible.
It’s just my personal opinion…
Thank you again, Jay, for sharing your experience!
Ahem,
John, not Jay 😉
Oops 🙄
Thank you, John
Great article, I too have an Anet A8 and almost had a melt down last night. I purchased mine a couple months ago and printed very similar modifications, cable chain, round blower nozzle, Raspberry Pi, ect. However, I did not upgrade the firmware until last weekend when I added a auto level. I was having issues with getting the new firmware to work correctly until I read about resetting the EEPROM. I flashed the firmware with the EEPROM clear and I didn’t realize what was happening until I started to smell burning plastic. After the flash the heater element when into high gear but the temperature wasn’t being displayed on the screen. I quickly uploaded the new firmware and then it restarted the temperature was maxed at 255 °C. As a safety precaution I replaced the heater element, thermistor and heater block. After reading your article I texted the wife to get another fire extinguisher for the house.
Inappropriate thin wire (Or insufficiently thick whatsoever.), heading from the control board all the way through the X-axis chain carriage and finaly to the undamaged heater, trying to deliver necessary current for very prolonged time, in lack of thermal runaway protection, is probably 99.99% source of your fire !
I agree with the original poster’s analysis, and think that your hypothesis is unlikely. Looking at his photos the wires that carry the high current to the heater show no damage near the board, only where they were burned by the chain that surrounded them.
Just to be clear. The Cable chain was the reason for the fire not the heat cartridge. The heat cartridge falling out was the catalyst but it didn’t start the fire. The cables we’re weak from constantly moving due to the chain, over heated and started the fire due to the printer trying to heat the hot end as the temp sensor kept reporting the incorrect temp. So the hot end cartridge heated to the max temp the firmware would allow, max 265 if I remember. You can clearly see the fire started on the motor side of the X-axis as that is where the most of the heat came from.
I do not agree with your conclusion. The wires would not have been “weak” from movement in the chain – it just doesn’t move them enough to cause metal fatigue or worn insulation in just a few years, and they would not have overheated. And had they actually shorted, they would have taken out the MOSFET driver if not a fuse. I continue to agree with the original poster that most likely the heater cartridge fell out and contacted some plastic – either the shroud or the chain, and lit that up. Otherwise the heater cartridge would still be in the block. The printer would likely have kept running for a while after that, so the heater cartridge could by then become displaced from the point of ignition.
Always good to have a reminder to keep an eye on your printer, and to have fire prevention systems at hand.
I do think your conclusion as to cause is wrong though, as the heater cartridge is clean, and not covered with burnt plastic. Assuming your theory of element coming free and touching the layer fan duct is correct the heater cartridge would be black and covered with plastic residue. Also the heat would be centered on the printer rather than one sided to the left.
I think you are probably close though. The root cause is likely the heater cartridge coming out and it being heated beyond scope. But I suspect your actual ignition point was the control board trying to endlessly heat the cartridge.
That fits with the heat being concentrated on the left and the flames melting the top spar there. And why your cable chain is sheilded from the heat by the nozzle block.
I doubt that the board was the issue, from looking at the photos – I don’t see any burn marks on the board. Also, as the heater got (presumably) hotter, its resistance would *increase* (it is a heater, not a semiconductor), and limit the current to something well under what the board could deliver.
My Monoprice printer did suffer from a problem where a connection at the board that partially melted a connector, and it finally failed to heat at all.
Photos of my control board at https://drive.google.com/open?id=0B2v4WRwISEQRRHU2Y1V6T1RiY2M
One can see the connector block slightly off angle in the first photo (without the inspection mirror), and see some slightly melted nylon in the second photo, via the inspection mirror. Rather than send the thing back (it was still under warranty), I did the repair, but told Monoprice that there was clearly a design issue with that setup…
The problem was that they had a screw block for the wire, but then a plug-in from that block onto the board. At the kinds of currents involved, even a pretty small contact resistance (such as between the part that clamped the wires, and the connector on the board) can cause a lot of heat. I replaced it with a one piece that soldered to the board with the screw connectors as part of that assembly. (Besides, the orange piece and the green piece underneath had effectively become one from the heat).
i taped the wiring of thermistor and heater together with kapton tape so one cannot get out without the other, and i check for temperature instabilities, and marlin is extra sensitive to it too, because when i got bad therpistor or not enough contact with heater block, it stopped itself.
A simple solution to this problem would be to secure the wiring to the heating cartridge in a way that prevents it from falling out of it does come loose. Then it can’t fall out and catch anything on fire. I have the wires from both the heating cartridge and thermistor zipped tied together. For either of them to come out of the heat block, they both would have to move. I also have that cable bundle secured to the carriage so there is not enough loose wire for them to slide out.
Glad your house didn’t go up in flames. Here was my disaster from 2011, that didn’t engulf my printer in flames like yours but merely melted the x-carriage:
http://www.keegan.org/reprapblog/archives/2519
Even better if you buy a smoke detector with a relay, and loop all printers through it!
What do you think of fire extinguisher balls? They seems like a good option if we were sound asleep or out of the house.
I absolutely think they are a good idea and plan on buying them myself.
Great article. Glass it was only a $200 lesson and not a funeral. Funny that this comes across my feed today as I just found my heating element sliding around on the block and the screw about to fall out… I have the wires tightly zipped to the bowen tube so no chance of it falling out… but this could be a real thing with this design. The hot cold hot cold temperature cycling will for sure work a screw lose very quickly. Tomorrow I’m adding lock washer for good measure.
I’m planning on doing a write-up of must-have and should-have safety features for your 3D printer, check back soon!
Very good article, I really appreciate you explaining the situation this thoroughly. I just ordered my extinguisher. 🙂
Aye, fire extinguisher & smoke detector ordered, thanks to the author for encouraging common sense safety measures!
This is at least the third article have have read about printer fires. I feel mine is safe, but caught myself checking the nozzle heater cartridge to see if it was loose. I have worked on and seen several printers that were acting up because of loose heater cartridges. If either the the cartridge or the thermistor come loose just a little the extruders normally act up. Currently using Repetier Host and they have a temperature trend which is quite handy when troubleshooting temperature related problems. I watch the printer temperatures on screen during warm up to monitor the temperatures (both bed and nozzle). If I see the temperature trends starting to wander away from normal its time to investigate before printing.
I did however add (2) smoke detectors in my work shop after the last article I read (all of the alarms in the entire house alarm if one goes off).