Wanhao i3 V2.1 catches fire



My i3 V2.1 caught fire last night. Smoke and flame were coming out of the power supply box. I opened the box up to see what went wrong and didn’t see anything obvious. So I plugged the machine back in turned it on. A flame started immediately from where the heated bed connects to the controller board. I pulled the power cord immediately. After looking over the wiring to heated bed and not finding anything out of the ordinary, I decided to turn it on once again to see why this obvious failure was not being stopped by a circuit inside of the machine. With my fire extinguisher handy, I turned it on once again. The flame built up intensity and smoke was filling the room but the machine never blew a fuse, breaker or any kind of safety device. After about 20 seconds I pulled the power again. This is a very concerning thing to see. Why is this machine letting something get hot enough to physically burn and not tripping any kind of safety device? I have seen electronics failures over the years but never anything that would literally start a fire.


Mine nearly did the same accept mine burnt a connection in the process which stopped it getting worse or setting on fire.

Check the the plug on the motherboard to the heated bed. You may well find its burnt. I spoke to wanhao and got a new motherboard and plug for the inconvenience.

Wanted to sue them for putting my family at risk though.


Once a fire starts in anything electronic, you shouldn’t turn it on again if you don’t know where it came from, because when something burns in an electronic circuit, it usually carbonizes things around the short, like the pcb itself, which in turn creates another path for current to flow through creating more problems, such as short circuits. It could have been just some play in the plug itself, that created a small arc that got worse over time, up to the point where things got hot enough to ignite the plastic. The heater is just a resistor dissipating quite a bit of current, so it’s not surprising that it can create such havoc. Do those cables move around enough to make the plug wiggle around?

If the problem is like Isleofyou3D’s photo, it doesn’t seem like there was a short circuit, so the machine couldn’t have known that something was wrong until there was either a short or an open circuit…

If you had unplugged the machine when you first saw smoke, you could probably have gotten away with cleaning the carbon deposits and getting a new plug, but after 20 seconds of it going up in flames, i assume the damage is now much worse.


Since you’re past the point of no return in that it’s actively catching fire when you turn it on (seriously, this is terrifying), your best bet is to contact wanhao for a new board. The connectors on the melzi board are known to not be up to the task of handling the current passing through them. If you’re up to it you can desolder the ones that come on the new board and replace them with XT60 connectors which will easily handle things without bursting into flame. If you don’t want to go down that route, another alternative is to solder the wires directly to the board and avoid using connectors at all. I have read of people using an external mosfet so that the board doesn’t handle the current to the heated bed at all, but it looks like the very latest boards have that build in to avoid this problem.
Rambled a bit there, but your best bet is to request a replacement from wanhao and insist that it be the very latest board with the mosfet to avoid this sort of thing happening again. I’ve had my 2.0 for 6 months now and no problems yet, fingers crossed.


My intention was not to minimize damage. My intention was to see just how far this would go. Wanhao seems to have a history of fire hazards and I wanted to see if this failure would lead to one and of course it did. After doing some research I have seen the information about the board connectors being under speced and causing problems. This in itself is unacceptable. If the community knows that there is a problem, so does Wanhao but they can’t be bothered to fix it. I also saw information that the firmware setting is not correct in Marlin for temp safety. If either of these 2 were properly executed (the board connectors or the temp safety setting in the Marlin firmware) this issue would not happen. I have found over a dozen instances that have occurred in the past two weeks where a fire or near fire has occurred for the same reason. This printer is a literal death trap and Wanhao doesn’t care. I would recommend redoing the wiring and updating the firmware if you want to keep using this printer. I for one am making Wanhao refund the purchase price and moving on to a company that has a better safety record and cares whether or not they are selling machines of death.

Rant over. Sorry but this has really stuck in my craw.


At the very least WanHAo should do a recall of all boards in the original 2.1 version and resupply latest boards updated with mosfets to ensure safety. Do they not realise that these machines are being used for lights out production in peoples homes. I’m all for DIY printing but if they get enough call backs they should move to reduce the problem instantly where lifes are concerned.


If history is any indicator, Wanaho does not do a traditional “recall” in the sense most of us are used to. I don’t know what, if anything, they will do but I don’t think their concern is safety over profit. Just search the internet for “Wanhao Fire” and you can see that almost every printer and version they have made has had the propensity to catch fire, including the new i3 Plus. They have had multiple opportunities to fix safety issues by making changes but have chosen not to do so.


I know there was a safety recall. Look at this it could be related to what you are reporting. https://groups.google.com/forum/#!msg/wanhao-printer-3d/ZXzxdP9SUlU/08waX466BwAJ


This information is for the original V1 and even though Wanhao likes to use the term recall, it’s not what you think it means. Wanhao posted the information about the problem on their group and left it up to the end user to determine if there was a problem. Wanhao’s fix for the fire hazard… electrical tape. Straight from their post, “In any case, you have found the crimp broken, Please cover it with insulating tape. If it’s beyond repairing, please 1. take a pic of broken heating tube. 2. provide your order No. and contact our distributor to get one free heating tube.” There you go, a Wanhao recall. It is posted on their group and individual owners were not notified. It’s up to you to find the information, check the printer yourself and then tape it or request a tube. This was also in August of 2015, a year and a half ago. Since then multiple revisions have been made to the printer but it still seems to be a fire hazard due to bad design issues that Wanhao does not want to address.


Well finally some good news, after being increasingkly disturbed by wanhao so called customer service who plainly told me that my metlzi board was at risk of overloading on the power and hotbed connectorstold me to change over the conns to screwins as any loosness would ramp the 13A that the board rated to to poss 25A, the conns being rated to 15A, so it was a k ocking bet that the board would overload and a fire ensue. I applealed to wanhao who promptly told me that they would only replace board under its 12 month guarantee period WHEN the board had BURNED. I retorted that I was disgusted that they would risk the lives of me and my family over this issue and I would not be running it. I said I would break down that machine send it back and ask for a full money refund. Nothing. So I wrote to Technology outlet that id boughtit from and asked if I could return it back to wanhao through them thinking it would be cheaper. a day after emailing them I got a reply saying the latest Meltzi board had been shipped to me and I would have it in my hands in 2 days. I did. Thank you very much T O. your customer service is nothing like wanhaos and I’m so glad.


I really don’t know what to say about this. I guess I could say that it’s good that you are getting a replacement board and that whomever (I’m assuming Technology Outlet) is providing that board has at least some integrity. But, the fact that Wanhao knows about the problem and is only willing to replace it after it catches fire tells me all that I need to know. To Wanhao money is much more important that human life or consumer property. They are safe in China and do not have to answer to a civil case in the US or UK. Since they know this, why would they lose $30 US per unit on the unsafe machines they have been selling for the past few years? It’s not like they would have to pay anything for their negligence no matter how people were killed or how much property was destroyed. The re-sellers carry less liability but still know they could be named in a lawsuit so they are more likely to help. Maybe the re-seller is just a good person that wants to make it right, which is even better. Either way it is clear that Wanhao doesn’t care about the consumer. I’m glad you are able to get a new board, let’s hope that they actually fixed the problem. They haven’t so far after several revisions so I’m sorry if I’m a little skeptical. Since you are doing the labor yourself, they could always say that you did something wrong to cause the fire. Just keep that in mind.

Best of luck to you and thanks for the update.


I have the machines dowen at the moment cause I’m moving premises but ill let you know when I startup again probs 2 weeks time. :slight_smile:


BTW I am now making my own cnc carriages for all sorts of headsets. that’s why ive got into the boards. :slight_smile:


I have a new I3 Plus I ordered in December. I have to had no issues but there is a simple solution. I am going to put in 15 amp fuses between the heaters and the boards if that is what the connectors are rated for. I would much rather blow a fuse than have a fire. I would also point out that this is a $500 printer. To some degree you get what you pay for so I am not surprised that their might be issues. I will say the print quality of the printer while not being nearly as good as my Makegear M2 has been acceptable.


I don’t take issue with you personally but the price of the printer is really not relevant. If a company were selling a $10 toaster that had a known defect and was catching fire would you say, “You should have bought the $20 toaster, I’m not surprised a $10 toaster catches fire.”?


I don’t think you’ve grasped the original thread here, wh are talking push fit connectors V screw in connectors. and the pips on the connectors themselves that go through the main board. its would be very easy to resolder in a couple of connectors but 1. the pin dia has to be what the board will take and its spaceing. if you look for connectors available they are rated up to 30A but have different siting dimensions. These do not allow you to simply change connectors. yes fuses would be a safty barrier but the problem is still then not being addressed . I am sure you would spend all your time replacing the fuses. this is why some have gone for external mosfets. the problem is the boards pinning holes and their spacing, I have just received the latest meltzi and it seems to have addresses the problem. Bad desesign originally has put lives in jepordy and maybe still is doing. this is more a warning than anything else about what to except from goods shipped from china. they don’t carry the same HSE standards that ours do. and if you realise that then at least you can prepare for it. Steve


The possibility of 3D printer catching fire also depends on the version of firmware that is installed ! More recent firmwares are more advanced and have the additional protection measures – like against a thermistor coming off place. For example, below you can find a commit message 43c298a (dated Jun 30 2014) from a Marlin Firmware repository. My cheap Chinese 3D printer (with Atmega 1284P) had a slightly older firmware version installed, so I had to update its’ firmware to enable this “Thermal Runaway Protection”! Always update a firmware of your 3D printer!!!

/*================== Thermal Runaway Protection ==============================
This is a feature to protect your printer from burn up in flames if it has a thermistor coming off place (this happened to a friend of mine recently and motivated me writing this feature).

The issue: If a thermistor come off, it will read a lower temperature than actual. The system will turn the heater on forever, burning up the filament and anything else around.

After the temperature reaches the target for the first time, this feature will start measuring for how long the current temperature stays below the target

If it stays longer than _PERIOD, it means the thermistor temperature cannot catch up with the target, so something *may be* wrong. Then, to be on the safe side, the system will he halt.

Bear in mind the count down will just start AFTER the first time the thermistor temperature is over the target, so you will have no problem if your extruder heater takes 2 minutes to hit the target on heating.*/


I am glad this issue is finally sorted out, I have had no troubles with the new board, in fact I have not set any PIDS and it seems to be fine straight out of the box so far. So if I get you right the thermistor is now set to check temp after initial warm up and go on doing that to be assured that the temperature is constant over time, if its not it shuts down the machine. I suppose this better than nothing and I’m not surprised with the Chinese mentality, but surley introducing more quality components and a safer physical guarantee, like using more quality heatrods that automatically pop when temp over permitted. they always seem to look at and go with the cheapest fix first. Thanks thought for your info, it has eased my mind more about “lights out production” although still not tried it yet. I do however let vmy hi res renderings run all night with no concerns, :slight_smile: . Thanks Ste


Hi Stephen, as you see from my comment below, “automatically pop when temp over permitted” is a firmware thing. Many of Chinese printers are using outdated firmware that is based on old Marlin firmware - which didn’t have these kinds of safety protections at this time. For that reason, I believe that every owner of cheap Chinese printer should manually update their firmware to the latest stable Marlin version, to avoid these possible safety problems, and improve the printing quality in general