Ask Hackaday MRRF Edition: 3D Printers Can Catch Fire

[Jay] out of the River City Labs Hackerspace in Peoria, IL cleared out a jam in his printer. It’s an operation most of us who own a 3D printer have performed. He reassembled the nozzle, and in a moment forgot to tighten down the grub nut that holds the heater cartridge in place. He started a print, saw the first layer go down right, and left the house at 8:30 for work. When he came back from work at 10:30 he didn’t see the print he expected, but was instead greeted by acrid smoke and a burnt out printer.

The approximate start time of the fire can be guessed by the height of the print before failure.
The approximate start time of the fire can be guessed by the height of the print before failure.

As far as he can figure, some time at around the thirty minute mark the heater cartridge vibrated out of the block. The printer saw a drop in temperature and increased the power to the cartridge. Since the cartridge was now hanging in air and the thermistor that reads the temperature was still attached to the block, the printer kept sending power. Eventually the cartridge, without a place to dump the energy being fed to it, burst into flame. This resulted in the carnage pictured. Luckily the Zortrax is a solidly built full metal printer, so there wasn’t much fuel for the fire, but the damage is total and the fire could easily have spread.

Which brings us to the topics of discussion.

How much can we trust our own work? We all have our home-builds and once you’ve put a lot of work into a printer you want to see it print a lot of things. I regularly leave the house with a print running and have a few other home projects going 24/7. Am I being arrogant? Should I treat my home work with a lesser degree of trust than something built by a larger organization? Or is the chance about the same? That said, my trust is also placed in the greater open source community at large. I know Marlin has protection built in to compensate for this failure, which is more likely in home builds than in a tightly controlled assembly process such as Zortrax is likely to have. However, I’m expecting that code I’ve never finely reviewed done by a person unknown to me to protect my home from a similar failure. It’s hard to predict the location of a critical failure with distributed development, and I’d love to hear the communities thoughts on it.

The other side of the coin is corporate responsibility. By all reviews and regards the Zortrax M200 is a wonderful printer. It’s well made, their software is great, and it prints beautifully. Even after witnessing this failure, it’s still my go-to recommendation for a printer for small engineering offices (especially if you’re the one who will have to support the “dang stupid print machine”). It is, however, as closed source as they come. The warranty is voided if you feed off market filament into it. They insist that you send the printer in for repair, even for routine things like an extruder jam. Under this information, we can’t immediately fault them for not having the foresight to see this failure mode, though it is horribly obvious in retrospect. So, if you made a modification or dirt standard to a repair out of manufacturer insistence, and a critical failure occurred because a common-to-hackers-fail-safe was missing, who’s responsible? Is the manufacturer right because they wanted to do the work themselves and control the input to their machine to ensure proper operation? Or is the user right because it’s their machine and, by all regards [Jay] is competent enough to perform the repair to his machine?

A cautionary message from [Jay]
A cautionary closing message from [Jay]
It’s also a very good case for open sourcing safety critical code. Someone might have seen this lack and just fixed it. Just like with the debates around encryption, if we can’t look into the code that we’re trusting and make sure the things we expect are there, do we really own it? I have a little more trust over my printer not bursting into flame because the parts were all hand picked for quality, I’ve read the code, and I am a fanatic about electrical connections. However, if I had the cash I would have a Zortrax on my desk right now, (and a few of the ones at MRRF, they are very nice) and I know I would trust it too. It’s a subtle game.

In the end [Jay] is out a nice printer, but luckily the damage was contained. Do you leave your printer running when you’re out of the house? Have you had a real or avoided disaster with something you’ve made? Do you have an anecdote about a commercial appliance with a safety oversight? Or do you just have thoughts about personal and corporate responsibility? We’d love to hear it.

79 thoughts on “Ask Hackaday MRRF Edition: 3D Printers Can Catch Fire

  1. There’s a setting in Marlin firmware to protect against exactly this problem, and it’s saved my printer multiple times before when a thermistor came loose. If it detects a miscorrelation between temperature and heater power, it stops the print and shuts off all heaters. I’d highly recommend anyone with Marlin turn that setting on.

      1. Firmware changes. Look in Configuration.h for “Thermal Runaway Protection”. The two directives you’re looking for are THERMAL_PROTECTION_HOTENDS and THERMAL_PROTECTION_BED.

        (Sorry for the delayed response, but I typed this from my phone this morning and haven’t been around my computer to look up what the configuration directives are called.)

        1. I discovered that a firmware of my cheap Chinese 3D printer was just slightly older than when “Thermal Runaway Protection” has been committed to Marlin firmware repository (commit 43c298a at Jun 30 2014). So I had to rebuild/update a firmware to add this protection

      2. It’s called “thermal runaway protection”. just google it you’ll get a lot of answers ;)
        Btw, even if it’s a good protection, the board failure’s always an option… so don’t take it as an ultimate security, it isn’t. My next printer is large size one, which means long time prints. It’ll be running a smoothieboard with 2 thermistors on the hotend and one inside the printer, + some custom code in smoothie to monitor everything. I’ll still use a separate security system (arduino + 3 thermistors to monitor printer, bed and board, and relay to shutdown the printer’s psu if something looks weird). But it still isn’t 100% secure. I believe it’s also important to have a metal printer, closed, if you want to run long prints. And to put it in a safe place (i mean, not a wooden desk in a wooden room, etc…).
        Anyway, i hate leaving a running printer alone at home. Don’t do that unless you can remotely monitor it and be at home fast. Really.

    1. Sadly, the current maintainers of Marlin are on a “features should be off by default!” mode. It took a lot of work to convince them that the watchdog feature should be on by default. And that’s just the first step of having your software protection properly in your machine.

    2. I was using Max6675 temperature sensing years ago with Marlin firmware. The fault checking available with the Max6675 was just thrown away by the Marlin Firmware.

      There are MANY options with the Marlin firmware, it would be a mistake to think all combinations are protected from temp sensor. If you print alone, I recommend running a test where you remove temp sensor from heat block to verify the firmware shuts down the heater correctly.

      1. Firmware changes. Look in Configuration.h for “Thermal Runaway Protection”. The two directives you’re looking for are THERMAL_PROTECTION_HOTENDS and THERMAL_PROTECTION_BED.

        (Figured I’d post this here, too, so you’d get this reply as well. I feel like this is a safety feature worth repeating.)

        (Sorry for the delayed response, but I typed this from my phone this morning and haven’t been around my computer to look up what the configuration directives are called.)

  2. Mine did almost the same thing. Back when Marlin didn’t have a “thermistor present” check, my terminal block got a bit loose while driving to my company for a presentation. When I wanted to demonstrate the printer in front of my colleagues it started smoking because it kept sending full power to the hotend while still reading 0°C. It still stings when I am reminded of that failure at work ;)
    Lesson learned: no terminal blocks!

  3. Place a connected smoke/fire detector above it so you get a warning when there is an issue or when you are asleep during those prints. There is even a auto fire extinguishers that you can place next to the printer. And you could integrate a thermal fuse in the printer that disconnects the main if needed

    1. You’d need one heck of an insensitive fire detector to keep it from triggering false alarms, given that you are melting plastics in the printer…
      One slightly more reliable way would be flame detectors, but those are expensive and require line-of-sight to the fire.

      1. Ive run a normal smoke detector in my home office without it tripping when printing various filaments.
        Its not a problem even with ABS. I have no additional ventilation at the moment.
        I will be doing the same again when we move but I also intend to introduce proper ventilation above the printers.
        We should all have smoke detectors as a minimum.

      2. Heat detectors are commonly used in places where nuisance alarms are caused by airborne “not smoke” particles. The disadvantage is that typically the thresholds are such that there needs to be an actual fire before any warning is given.

    2. There’s also flame sensor modules you can get for cheap from the usual Chinese suppliers. And from this: , they do seem to work well. Vid link to board:

      This adds yet another sense (and feedback) to our currently fairly dumb printers. I could also see how an outside module with this hooked up could have the ability to kill power to the printer as well as spray some fire retardant. I’ve yet to see anything like this.

  4. My commercial expensive coffee maker (Krups brand) caught fire while it was brewing coffee one morning. It turned out that the mains supply wire (coming directly from the plug) touched the heating elements inside, insulation degraded over time and finally an arc started. I had luck that this happened while someone was around…

  5. My heated bed SSR board bought in off ebay as a module but osh design to try and keep the load down on the printrboard connector pins + also so I can use a seperate psu to run printer + bed. Its not part of the printrbot itself but a addon mod I’ve done so my fault not pb.
    Nowhere in the instructions did it mention external heatsinking and I was being a bit dull and tucked it away out of sight with the rest of the other electronics. I’m going to replace it with another of the same design but mount it in a dedicated diecast alu housing to contain any fall out and also to use the housing as a heatsink for the fet, as I think root cause is I baked the fet with heat soak. It ran for about 30 hrs print time like this without a issue before suddenly *pop*, though I can’t rule out the wire terminals loosening with vibration that I had used on the bed side to keep the bed detachable during maintenance, so I’m going to toss them and solder all wire in perm next time.
    Yes I do leave my printer running unattended though the room has a fire alarm without anything combustible nearby and on this occasion I was eating in the kitchen and heard the fire alarm go off, to come back into a very smokey office and the printer still happily printing away in the middle of it. Took 2 days to get the stink of burnt fet out, but no harm done to the printer itself apart from two wires with their insulation damaged despite the relay board being mounted underneath with all the other electronics.
    Could have been a lot worse but by then I would have expected the psu protections to have kicked in due to shorting or overvoltage and house is wired with modern elcb etc, & I’ve had commercial stuff go up in smoke, and I’d trust my printrbot over some cheap plastic cased consumer item. Smoke alarms are cheap. We have 6 throughout the house but its legal minimum to have two per property here anyway. I won’t be running any jobs lights out overnight while we’re asleep again like I have in the past though until I find room in the workshop in a outbuilding for the printer to live where other machines do the same.
    Image :-

  6. What firmware was it running so we can make sure to make some noise about it. I know Marlin and Repetier have these protections along with Redeem. I think Smoothie now has it but only after pulling teeth to get it.

  7. I have a thermal fuse inline for the power supply wired near the hotend — if something catches fire, it should kill the power. and at the top of the frame I have one of the range-hood ‘poppers’ –a small fire suppressor
    I still try to schedule things so that I don’t need to leave any appliance running when I’m asleep or away

    1. This. Thermal fuses and thermal switches are cheap and reliable. I have 125°C fuse near my hotend and heated build platforms, plus a resettable 50°C switch in the box where I keep the printer.

      1. How do you know the fuse is close enough and is going to trigger if the hot end fails?

        I looked into these too, but I couldn’t work out what value to use, and where to put it.

  8. Most of the meltdowns I’ve seen people post have been are the wire-to-board connector, namely loose wires, good wire management is the answer there.

    That said I think that hotends and beds should really have two thermistors each for redundancy, if they don’t agree within a close range, shut down the heaters and stop the print. If they are not increasing when the heater is on, shut down the heaters and stop the print. If they change suddenly by a large amount, shut down the heaters and stop the print. When running properly the temperature is pretty stable, slow moving, and predictable, it seems like something that can easily be checked.

    Even excluding fire hazard, I would much rather have a print paused at the first sign of a problem, and possibly be able to salvage it, than to have a problem continue for an hour or two and be left with a hopeless mess.

    1. “Most of the meltdowns I’ve seen people post have been are the wire-to-board connector, namely loose wires, good wire management is the answer there.”

      Guilty as charged!
      My leads were loose, snagged the print and ripped out the thermistor!
      This was the second time, the first ripped up the cartridge!

  9. I think I read somewhere that you can hack a smoke detector and wire a normal closed solenoid to it. In case of detected fire smoke it will cut off the power from the printer. This would be a good idea if the firmware locks up or the heater is activated by a bug or loose thermistor or heater cartridge.
    I wonder if an enclosure would’ve helped, if the oxygen is depleted the fire should go out right? The enclosure should be really tight though, and dangerous fumes of carbon monoxide will be there. I own a wood frame prusa i3 and curtains nearby so the damage would’ve been much more extensive if it caught fire.

    It would be a good idea to have a separate safety system from the printer firmware in case of bugs and other failures.

  10. I’m paranoid, I can’t leave the house or shop with anything powered up except the washer/dryer. These printers–even the (non-Stratasys) commercial ones–are more science fair projects than not. Anything that uses enough electricity to make fire needs either more safety engineering or to be babysat.

    1. I had the heater elements inside a drier short to the chassis- I was there, noticed a funny sound, and saw them glowing red hot when I stopped it! Drier lint inside the machines, vent hoses, etc. is a big fire hazard.

  11. Having a Zortrax here at the office. On one hand, it’s a decent looking machine. But safety it lacks. This fire shows. But also, the bottom of the machine we have is open. And you can just grab into the 230V connections to the power supply. Later revisions added a plate on here to prevent this.

    I’ve lifted the firmware blob from their firmware update. But with quick inspection I think the blob is compressed or encrypted. Didn’t try anything more with it. They are running on a ATMega2560, so the interrupt tables should come up as an very easy pattern to spot.
    Would be good to reverse engineer to see if they violate any GPL firmware.

    Note, their closed eco-system also requires you to enter your machine serial number to download anything and to activate the slicing software. The files the machines reads for printing are binary, but can most certainly be decoded, as I see clear repeated patterns in it.

  12. Yes its a legit concern. These devices are research and development prototypes that came of age and went to market before ever becoming more than a research and development quality device. Safety was and is an after thought because the people doing the research and development are extremely intelligent, know the risks , do the work themselves and do their work as well as they can. In the early days development was a very tight nit group that all knew each other to a degree. As people tried to get rich on the idea they never got actual design engineers and released a poorly thought out product that was never actually intended to be a consumer based product. PEople make it increasingly easy to utilize the design but this instills none of the intuition needed to identify issues before it burns down the house. IT is the design that is lacking. Safety was NEVER a major concern. The entire thing needs to be designed for safety for these fires to not be an issue.
    No I dont leave my printer running unsupervised.
    In your example I feel the company would be at fault for using a house fire as their intellectual property watch dog. Its a bad design and shows at best incompetence at worst willful disregard for the customers life, property etc.

    This is what happens when people who have no business designing consumer products see an opensource design and try to get rich (on a research and development design they didnt make ) in my most humble of opinions.

    1. Full question: “So, if you made a modification or dirt standard to a repair out of manufacturer insistence, and a critical failure occurred because a common-to-hackers-fail-safe was missing, who’s responsible?”

      Short variant: “if you made a modification, who’s responsible?”

      No joke. A real question. If you make a repair to a machine, who is responsible when the machine messes up?

      1. I’m no lawyer but I’d bet money that there is plenty of case law out there going either way. One could argue that if the manufacturer did not make it reasonably inaccessible except by a qualified technician then it should be expected that the average person with basic skills can and would attempt to effect a repair themselves. Especially since it can be expected that a good portion of the owners of these machines are very mechanically inclined.

        Were there obvious restrictions in accessing the dangerous parts like specialty screws and plates? Were there any obvious signs that stated no serviceable parts inside or certified technician access only? If not then Zortrax could still be on the hook if a good lawyer was on the case.

      2. If you repair something and it messes up then you are responsible.
        The manufacturer has warned you against doing it yourself.
        You don’t have any technical documentation about how to properly carry out the repair.
        You don’t have any documentation about the safety features present, certainly you shouldn’t assume they exist.
        If you make a modification then it is up to you to make sure it is suitable, it’s not fair to blame anyone else or to say they should make assumptions about what you will do.

        There is a lot of fuss made about what constitutes a void warranty but the truth is if you want to modify or hack something then you shouldn’t really care about the manufacturer fixing it for you.

      3. It’s going to vary by jurisdiction, but a typical answer is that if you’ve done something stupid, and/or ignored warnings, you are. If they’ve got a really flawed design and you work was reasonable to expect to be done, they may be (e.g. installing a car stereo shouldn’t disable airbag, even if you voided warranties.)
        However, given the closed nature of it, and the experimental nature of printers as noted above, seems likely it’s your fault in this case.

  13. I’ve been wondering when this sort of thing might start popping up – lawsuits when someones McMansion goes to ashes as their Christmas MakerBot gives up the ghost are sure to follow.

    Good engineering design (which many of these project-level products don’t exhibit) must accommodate multiple (mis)use and failure scenarios (teaching undergraduates will provide a broad lesson in unanticipated difficulties). Basically I treat *everything* I build as if it’s going to fail badly since it only takes one occurrence. Hot wiring a smoke alarm and other remedies are a good idea, but eliminated the hazard source is best if possible.

    “Power it down when you’re not around” is a good place to start. For small battery/wall-wart blinkies using commercial boards I may leave the low-voltage logic side powered up but if there’s significant power available to the build, there is the potential for bad things to happen.

    There’s an off-switch for that.

    1. “Power it down when you’re not around” – but then it can not do the work it’s supposed to do. Especially 3D printing takes often several hours. I don’t see it as an option in this case to power it down when Ieave. If it is potentially dangerous then there should be safety mechanisms. For example washing machines have different safetys against flooding by a broken hose and of course against fire. There are several thermal cutouts. Industrial control has various levels of plausibility check, which is mentioned in the article for the printers also. Like if applied heater power does not lead to the appropriate temperature rise on the sensor.
      Even if I am at home I could have been tired and fallen asleep. Then the smoke could be deadly even without a full fire. So make that devices safe enough to not require continuous supervision.

    1. Who forbids this? I expect devices (especially something like dishwasher, washing machine, dryer,… which take longer time for their job) which are safe enough to leave them working alone.

        1. I am sure the dishwasher was listed by a rating agency as well- though CE is a “self rating” Every dishwasher I have seen has a thermal cut off or two- but no good to stop a fire once it is going. I am not familiar with the approval/rating system in the UK.

    2. Your insurance may not cover water damage from leaving an appliance on either.

      Some of my relatives just had 30,000 in water damage from a toilet valve that failed. Pretty simple mechanical device, with no programming at all!

  14. There are a few safety faults in current 3d printers.
    First is the high current demand on many devices. Using a heated bed on 12v can draw anywhere from 10-16 amps. If you’ve ever spec’d out wires and connectors for 16 amps you would understand how ridiculous this is. Most of the connectors and wires are underrated.

    People running old firmware that doesn’t have safety checks for heater response. Most old firmware does not have a method of checking to see if temperature is changing when the heater is turned on.
    Watchdogs are not used. A lot of the firmware out there does not have watchdog timers enabled.

    Other improperly rated components. With up to 16 amps being drawn through the heated bed, there are other components that are not rated properly. This includes Mosfets, power supplies, and PCB trace width. do you have any idea how wide a trace you need on 1oz copper that can support 16 amps? at least 1/2 an inch wide!

    Redundant safety devices are missing. Thermal fuses are commonly used in devices to prevent catastrophic failures, but you won’t find any in a low cost 3d printer.

    1. Most printers are running on 24V. (ours are) Especially with large heated beds, as it’s hard to find power supplies that can supply that much current.
      (Excluding home build RepRaps, those people sometimes to crazy stuff)

      Thermal fuses, we tried that, but fitting one in the design space that triggers in time did not work out for us. The connections for them are still there if you want this (On the Ultimaker2 products and Ultimaker Original Plus)

      Watchdogs have always been on in our firmwares, and with the UM2 I added an extra check to protect against the rare case where the heater moves out of the cartridge.

      I tried my best to have the watchdog enabled by default in mainline Marlin. But my time and patience is limited.

      1. Most printers actually use 12v or an ATX power supply. Ultimaker is one of the few that takes safety into consideration, but most makers buy whatever cheap printer they find on amazon or ebay (under
        $800). In fact there is a growing market in these low cost printers, which means we will see growing news of printer or house fires.

        For the thermal fuses, most are not the resettable type, which is why you see so many appliances die when they overheat- the thermal fuse blows. Ideally you would have the 125c fuse on the bed, and a 300c fuse on the hotend,, each inline with the power wires, but you’re not going to find easily accessible 300c thermal fuses, or ones that can take that high current.

  15. What happened to the first rule. Don’t leave a printer doing it’s thing unattended. He is lucky all it messed up was the printer.

    Before you all jump on me: what about long 5+ hour prints? You don’t have to watch the printer the whole time but leaving the house was pretty trusting.

    1. Sorry, I do not think that logic flow is acceptable. 5 hours is medium time for a print. High quality prints can go up to 40-60 hours.

      As a printer manufacturer I do not think you can hide behind “but you should not leave it running unattended”.

      (FYI, I work for Ultimaker. Yes, most of our testing fleet of printers runs over the weekend. No our building never burned down. Yes, we had fires, in our laser-cutter. Do not leave those unattended. But our 3D printers never caught fire, unintentionally)

      1. Yes, the label is a cop-out. I wonder if it would open a manufacturer to more liability than not, as it is obvious to everyone that it is MADE to make long prints. (especially if it is a big printer!)

        Better warnings might include keeping it away from flammable materials, making sure wiring is in good shape, checking belts and mechanical systems, using only listed power supplies and cords, providing thermal cut-outs, etc.

  16. This is all on Zortrax if the end user was using the stock firmware and did not majorly modify the design (i.e. bypass safeties). Single point failures that result in a fire are never acceptable in consumer products.

  17. I’m not an EE, but I was taught some engineering skills when training as an electronics technician. We did exercises with small circuits in which we had to list all the ways each component could fail and describe what the circuit would do in the case of each failure. That seems like a good exercise for any project. What if this part broke? What if this part broke? What if this screw came loose? What if this screw came loose? Etc.

  18. It’s not reasonable to rely on the hardware that does data processing to also provide safety. It’s far too prone to crash or hang up or do whatever to relegate safety features to this hardware. Temperature checks should run on dedicated hardware. Ideally, you’d have a mathematical model of the print head; feed it with heater on/off and filament flow data, and check the temperature of the real print head against your model. If they are too far apart, there is some error, so stop the print.

  19. I assume the Zortrax printer is not UL listed. Underwriters Laboratories would do things like removing the heater or thermistor from the hot end and cutting thermistor wires to see if it goes up in flames. Bypassing and testing thermal cutouts in kitchen appliances that generate heat is a large part of their testing.

    Bypass to see how or if it burns if the cutout fails, testing the cutouts to see if the ones installed open at the right temperature or if they fail.

    Zortrax not having a flaming obvious safety feature that’s in millions upon millions of other consumer appliances and electronic devices – that’s all on them. They should give Jay a new printer and a big thank you for discovering the safety hazard with their printer.

    Mattel’s new Thingmaker 3D printer is definitely going to be subjected to those tests and even more tests than equipment expected to be used by adults gets. Can’t have any possibility of hurting the kiddies in any way instead of relying on telling the kids “See this? Don’t touch it because it will burn you. Don’t stick your finger in there because it will pinch it.”. If people are never expected to learn about dangerous things, they get hurt or killed when they encounter dangerous things because they grew up believing in an inherently ‘safe’ world.

    1. UL and other NBs are just now starting to get a handle on 3d printer assessment, where the equipment category is referred to as ‘additive manufacturing’. In any case, do not believe that any new standards are required (UL would have you think different), as the relatively new UL62368-1 is quite capable of addressing all hazards for this stuff. They have convinced ANSI and SCC that we need a whole pallet full of new standards (

      In any case, in these United States, it is federal administrative law (29CFR1910) that all electrical equipment used in the work place bear the mark of an NRTL(CSA,ETL,Nemko,TUV,UL,etc). As for people that insist on burning down buildings with hobbyist stuff – go for it, electrical equipment and construction industries need the business. Idiots.

      1. Never mind all the import crap that bears an official-looking UL logo/hologram but which UL has never seen, let alone tested to death. It’s hard to trust things any more.

        1. Have seen more business and residential fires caused by legitimately-marked (NRTL) equipment than have seen from stuff with no agency logo or counterfeit agency logos. The concept of ‘forseeable misuse’ is difficult to address in either the product design or in the safety (Type) tests indicated by ANSI (UL) safety standards. The many IEC technical committees writing standards, and the many product assessments done by the various OSHA-registered NRTLs will never overcome the Dark Side (aka, the power of human stupidity).
          As for counterfeit marks, all NRTLs and SCCs have websites to look up equipment models that has been assessed and certified per a standard or directive. And have never seen a counterfeit mark that was not identifiable as such after 45 seconds of observation.

          1. Re: the counterfeit mark part. To the common person it’s obviously not as simple as 45 seconds of observation. Those who don’t work in the field professionally, or aren’t deep enough into the hobby side to care, don’t even look at the logos. Plus the general public wouldn’t know how to process the information even if they did bother taking the time to compare/look them up (yes, it’s probably readily available and easy to find. but they’re the general public – either plain lazy of willfully ignorant). I’m just saying. To somebody like you (i’m assuming you work in the field) – sure it’s dead simple… but you look at that type of shit all day.

          2. There’s a huge business in selling on eBay counterfeit Samsung chargers for the Galaxy S4 and Tab3 and newer Samsung products. Why? Because Samsung slaps a $40 price on a $10 charger.

      2. Some of the dumbest electrical work I have seen is by professional electricians and contractors, signed off on by city inspectors. Electricians can take your listed and marked water proof (type 4X) stainless enclosure,punch holes in the top and connect EMT to it with no appropriate hubs nor gaskets! All with three phase 460VAC in the box, in a wet environment. No problem, they are licensed. Inspectors have their favorite issues, tend not to know much outside of what they usually see daily (same with electricians and contractors), and are often completely unaware of anything new or better (I know from trying to explain the code to them on things like VFDs, or more basic motor protection). If you are one of their known contractor buddies you can do whatever, they rubber stamp it without much thought.

        I have dealt with UL for industrial control panels and manufacturing – they love to have a new requirement so they can make a new standard and charge for it. Try to get help from them figuring out their byzantine organization if you want to list something not in a standard category. I see many UL listed things that I would never put in my house- like light fixtures that have crappy small gauge wiring with cheap crimps and insulation that is asking for trouble. Or how about all of the metal lamps that have completely ungrounded metal parts with cords winding through them. It met the standard though. It is “safe” in so far as it will not kill anyone or start a fire right now, even though it may fall apart in a year!

        end of rant.

    2. UL does pretty straight forward safety testing- I think your idea of the level of testing they will do no this device is far beyond the practical reality. They will likely test insulation and grounding, insist components are listed or recognized (by them), have basic standards for electrical construction, run the device for X number of hours and measure temperatures, making sure it does not catch on fire. That is it.

  20. I had a 3D-printer incident recently on a RepRap Huxley, one of the tracks on the hot bed caught on fire. I smelled it from another room and went to investigate but the printer still worked fine so i started looking for other sources. But when the print finished i noticed the bed was cold. It took three days for the smell to disappear.

    Recently i bought a Wanhao Duplicator i3, it feels a lot nicer with a printer made mostly from metal, but i’m going to check how it deal with incorrect feedback from the thermistor.

  21. this is out of my usual wheelhouse, but iirc your attempts to repair your car cannot void the warranty, per SCOTUS.

    i could be asswhistling here, but if this is the case, simply opening the case of your proprietary 3d printer cannot automatically void the warranty.

  22. Adding my data point here, a certain brand of fast charger decided early (1.30am) one morning to immolate the attached USB cable resulting in smoke but fortunately no flames.
    Turns out that if these get slightly damaged a fire is a real possibility, the trigger is normally damp but can occur from any sort of liquid damage which is likely if you charge your phone in the winter near a window for example.

  23. Maybe the fix here would be to install the printer next to a smoke alarm, set to cut the power and alert the user via SMS in the event of smoke/excessive heat buildup being detected? Photoelectric would be better as they can be configured to deal with small amounts from a particularly fumey filament eg ABS.

  24. The second you think you have “safety critical code” you need to stop and consider how a hardware/software failure could cause a fire, burns, electrocution, an explosion, whatever! In programmable industrial equipment there are always stern legal warnings about depending on anything programmable for human safety. You can make programmable things time out with watchdogs, look for unexpected sensor results (like the disconnect between a heater being on full blast but no temperature increase) , call for help, and attempt to shut down or fail in a safer way. Ultimately however, you need safety to depend on non-programmable devices like thermal cut-outs (unless you have the resources to design and verify redundant programmable systems as “safe” within certain conditions). Every appliance has thermal cut-off devices to shut down power in the presence excessive heat (hopefully before a fire is started!) I am concerned about this issue with 3D printers, lasers, etc, and a little skeptical of kit and do it yourself suppliers feeling they have done their duty with a warning label not to operate the machine “unattended”. That is utter nonsense for a device with a print bed size where you can easily set up prints running for more than a day. I am glad the open source community has discussions like this, and encourage all experimenters to add safety features to printers, interlocks and enclosures to lasers, ground fault detectors in workshops/workbenches and be aware of keeping projects reasonably safe!

  25. Unfortunately a similar incident was reported in today’s newspaper in Austria. A 3D printer catched fire during the night, people woke up, owner tried to fight the fire with a powder extinguisher, but was not successful. The fire brigade was able to fight the fire and protect neighboring apartments or buildings but this apartement is reported “unusable”.

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