Will your 3D-printer kill you?

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Will your 3D-printer kill you?
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Will your 3D-printer kill you?

As the 3D printers spread around the world, a fact that some people call the "new industrial revolution", there are more and more concerns about the dangers surrounding these machines. The most common desktop 3D printers use the Fused Filament Fabrication (FFF) process or Fused Deposition Modeling (FDM, which is a trademark of Stratasys Inc.) process, so we will talk about the dangers of this kind of 3D printing process.

The dangers around a 3D printer are infinite. It's never too late to say that this kind of machine isn't a toy, so CHILDREN SHOULD USE THEM ONLY UNDER A RESPONSIBLE ADULT SUPERVISION. The caution advised is the same as to drive a car or use heavy machines: call someone who knows what to do if you don't know what you are doing otherwise it can cause you severe injuries and even death.

As the general dangers of the 3D printers, we can point out:

  • Electrical dangers in 3D printing:

The power supplies used by 3D printers usually are either repurposed ATX (personal computer usual power supply) or enclosed wall power units, such as used by laptop computers or by Xbox (highly used due to its low price and its endurance). Brazilian makers use also 30A switching power supplies. Re-purposed ATX and enclosed wall power units are already UL listed and tested. The switching power supplies need more attention on the wiring but don't represent a real danger if correctly connected. Most of these power supplies don't exceed 24 volts, including the power sent to the hot end and heated bed, so they don't represent a real threat for electrical shocking. The real danger about it is a short-circuit in the wiring, that can cause electrical failure in the room/house and/or fire. To minimize this danger just take real attention to the wiring and the use of the right electrical components for it. But is really hard that this electrical danger can kill you.

  • Mechanical dangers in 3D Printing:

There are obvious safety concerns about it, like threaded rods, belts and pulleys pinch fingers and other things. Besides, things like threaded rods and belts can pull long hair, necklaces, etc. It's impossible to have a working machine without these components, so using a bit of caution and, as in a roller coaster, keeping "hands and legs inside the vehicle during the ride" (i.e. DO NOT STICK ANYTHING IN THE MOVING PARTS) you will be fine. In 3D printers like Makerbots or Ultimakers (that the moving parts are inside a box) is even easier to avoid these mechanical dangers.

  • Thermal dangers in 3D Printing: 

There are a few components that can burn you other are just uncomfortable for touch, but there's just one problem here actually can kill not only you but your whole family and neighbors too.

The stepper motors can get hot but not enough to burn you because they heat up to 60°C (140F) and some even get to 80°C (176F). Also, you should remember that the stepper motors usually lose steps when they get higher temperatures and this messes with your prints, so it won't kill you, but will surely make you (really) angry.

The power supply are usually covered units, but they need to have proper ventilation because they dissipate heat as they work. The temperature is not a big deal, it won't get hot enough to hurt you. But keep in mind that if the power supply overheat it will (at least the ones with overheat protection) stop working (i.e. shutdown) and this will be a real headache because this kind of problem will only show up on a really later time of the print (i.e. last layers). And this, also, won't kill you.

The build table (a.k.a. heated bed) is where you actually print the parts on the 3D printer. This surface can be heated to different temperatures depending on the filament material and if there's a glass (mirror) over the heated surface or not. If is used with ABS filament over a glass surface usually is heated to 120°C (248K). When used with ABS without glass surface is heated to 100°C (212) or to 110°C (230K). If PLA filament is used a heated surface is not needed, but if the user really wants to heat the surface it goes to 60°C (140K). Most of the printers have markers on the heated bed a warning signs saying "HOT SURFACE" and "Do Not Touch" because of an actual UL requirement for certified 3D printers. It can hurt you due to the temperatures reached, but won't kill you... Except if you have one problem that we will talk about soon: a temperature sensor misplacement or malfunction.

The hot end of a 3D printer is where the filament is heated to the extrusion temperature by the heater block which has some sort of heater (a heater cartridge or an electrical resistance or something like it) and a temperature sensor. The PLA filaments usually 3D prints from 180°C to 200°C and ABS filaments uses temperatures from 200°C to 220°C normally, but I've noticed people using PLA filaments at 220°C and ABS filaments at 240°C. The temperature needed depends on the position of the temperature sensor against the place of the tube where is the filament going to be heated and the heater element. If the temperature sensor is nearer to the heater element than the filament tube higher read temperatures are needed and if the filament tube is nearer to the heater element than the temperature sensor lower read temperatures are needed. This is because the temperature read by the temperature sensor would be different but the temperature on the filament tube must be above a minimum to melt the filament. Other kinds of 3D printing filament (like Nylon and Polycarbonate) need even higher temperatures. Recently, some 3D printers models showed up a protection around the hot end and others showed up enclosed in some sort of boxes that only let access the hot end through a door. These most recent models were created to attend UL and CSA requirements for finished goods, where the protection of the user is most important. The working temperatures of a heated hot end should not be able to kill you, but will create a scar for a long time (a.k.a the rest of your life). At last but not at least, we find  the same problem I just mentioned when talking about the heated bed, the only problem that could make a hot end kill you: the temperature sensor misplacement or malfunction.

We told before that the temperature sensor misplacement or malfunction could kill you, your family and your neighbors, remember? Take a look at these pictures and the story behind them:

The burned 3D printer of Claudio Sampaio.
The 3D printer that caught on fire.

The burned room of Claudio Sampaio.
The room burned by the 3D printer.

The burned workbench of Claudio Sampaio.
The workbench burned by the 3D printer.

Claudio Sampaio, a brazilian maker and "reprapper", showed off his story on 06/25/2014. "This happened a few weeks ago. The worst part is that the board was well tuned. I had two multimeters monitoring the temperature on the hotter parts, showing that was running smooth. There was passed 12h from a 22h print and I decided to go to the bank. I've been out for an hour, no more than this. When I came back, the house was full of smoke. I took the CO₂ fire extinguisher and the gas mask and extinguished the fire from the printer. On a rack next to it there was 4L of acetone, 2L of pure alcohol, 1L of chloroform, 1L of sulfuric acid, 1L of tetrahydrofuran (THF) and 1L of dichloromethane. Imagine what would happen if the fire could get to the rack..." said him. The whole reprapper brazilian community was concerned with this accident and talked over this. Then Alex Borro, who also was one of the Marlin firmware contributors, implemented the Thermal Runaway protection on Marlin firmware which was then merged with the official branch and is available until the latest version (1.1.0). The thermal runaway protection works separately on each heater (the hot end and the heated bed) and doesn't let the heating element on after a determined amount of time if the temperature doesn't show a significant change in this period. Using this protection, is even harder a temperature issue kill you.

  • Chemical dangers / dangerous gasses from filaments:

Probably this is the more problematic issue and more dangerous problem than all the other mentioned. Makers that have a gas detection equipment (not talking about smoke detectors, OK?) is not as usual as the ones that have multimeters. Most of the people use only its nose to detect this kind of danger. Useless to say that this is the wrong way to do it. The plastic that is changing its state (i.e. heating and melting) typically emit fumes and odors. At least two studies were done about this subject and each one of them shows exactly the opposite conclusion than the other.

The first research about the fumes that we found was the one available at Instructables, which was posted at September/2012. This research is told as the first one about this subject and use the most cientific process possible to be done outside a research laboratory. They searched for HCN (hydrogen cyanide) on the fumes of the 3D printing process following injection molding standards using ABS filament and Nylon filament from some different sellers.

Box used on fumes testing.
Fumes test range by Taulman group.

They found out that in normal 3d-printing conditions any of the tested filaments showed a significant percentage of HCN. So, 3D printing is quite safe then, right? For them, yes, but remember that they are also filament sellers. Their test showed that for the ABS filament there was no HCN measure for any of the different brands available for the test. A result with no HCN measure was found also for their Nylon filament (the filament that they actually sell). The Nylon filament that they tested from other sellers (which was actually trimmer and weed-whacker lines available in home improvement stores) were also safe for 3D printing but showed off 0.1 ppm of HCN in their measure. We think that this is a tendentious result for the only reason that they actually sell the filament. How could them sell something and also say that is dangerous? So, what is the truth? Well, at least, one thing we can point out to show how this research was a bad reference: they just looked up for HCN generation and this isn't the only danger that a 3d printer filament fume represent.

We found a most recent research about the filament fumes, a paper published online on January/2016 and printed in February/2016. The paper was published by the American Chemical Society (ACS) and is freely available on Environmental Science & Technology website. The same research group made an article about the same subject, but with less 3d printer brands and less kinds of filaments involved.  We read this paper and this is what we can point out:

  • The ultrafine particles (UFPs, particles less than 100 nm) and volatile organic compounds (VOCs) are (presumably) dangerous AND emitted by the FDM/FFF 3d printing process;
  • They used a more complex test chamber to avoid external interferences (picture below);

Fumes emission test chamber.
Fumes test chamber used in the ACS article.

  • Five commercially available filament extrusion desktop 3D printers were used within up to nine different filaments on the test with each 3d printer;

Table of All Experiments on ACS article.
Summary of all experiments on the ACS article.

  • The 3D model used (NIST standard available here [download id="4027"]) was the same on every test (except one) and contained a variety of features that could also influence dynamic printer emissions, including a combination of solid volumes, thin protrusions, holes and indentations;
  • The 3d printer beds were ready according to the manufacturer recommendations, depending on the printer and on the type of filament used;
  • They, at first, determined that the particles emitted by the FFF printers were in UFP size and used a condensation particle counter (CPC) equipment to measure the number os UFPs emitted;
  • The function they used to "smooth" brought an estimated uncertainty of 45% to the UFP emission rates calculated;
  • The UFP concentration usually increase quickly just after start printing and stay like this for the first 10 - 20 min, when it begins to decrease, but still stays higher than the background concentration;
  • The UFP emission rates varied depending on make and model of the printer, type of filament material, time of printing, nozzle temperature and bed temperature.

Summary of UFP emission rates.
Summary of time-varying UFP emission rates on all experiments of the ACS article.

  •  The highest UFP emission rates occurred with printers using ABS filaments and the lowest occurred with the printers using PLA filaments. The other filaments showed UFP emission rates between ABS and PLA;
  • They also found that the shape of the printed part don't change the UFP emission rate, as they changed from the NIST standard to a cube and the measures haven't changed much;
  • The presence of an enclosure only moderately reduced UFP emission rates, but the enclosures were not sealed;

Summarized estimates of VOC emission rates
Summary of estimates of VOC emission rates.

  • Filament material made the major difference in the types of VOCs emitted, but the printer make and model made the major difference on the overall mass of VOCs emmited with the same filament.
  • The lowest VOC emission rates were found with polycarbonate filament and the highest were found with nylon filament, both on the LulzBot printer;
  • Nozzle temperatures didn't have a large influence on UFP emission rates on low (less than 45 °C) and high (100 - 110 °C) bed temperatures, but on midrange  (60 - 65 °C) bed temperature the UFP emission rates were higher with higher hotend temperature;
  • Printers with highest bed temperatures had the highest UFP emission rates and the ones with lowest bed temperatures had the lowest UFP emission rates;
  • The VOC emitted in large amounts by ABS and HIPS filaments (styrene) is classified as possible human carcinogen, the one most emitted by nylon, PCTPE, laybrick and laywood filaments (caprolactam) isn't carcinogenic (but have exposure time restriction) and the one most emitted from PLA filaments (lactide) isn't toxic at all;
  • In the worst scenery (small office with low ventilation and the higer emissions of UFPs, styrene, caprolactam and tactide), the operator of the 3D printer could be exposed to dangerous amounts of VOCs.

As this is a group of researchers that have no bond to any filament seller company, we think that this is a most reliable result. But, as they say, the "smooth" function they used on the collected data brought uncertainty of 45% on their estimates.

Then, we can conclude that a 3D printer can kill you on a long-term use on poorly ventilated spaces. Yes it CAN kill you, but only if you let the machine do it. The UFP exposure on the worst scenario isn't a real problem, because you can find similar exposures on a variety of situations. So, to avoid the problems with the dangerous VOCs, we strongly suggest an enclosure for all the printers (as most of the 3D Systems and Stratasys printers have) as a way to avoid the risk, because you can either put a combined gas and particle filtration systems or, at least, avoid warp when printing with a windows open. In case an enclosure is not possible or you can't have a proper ventilated room, you should stick to PLA filaments, it won't kill you.

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Written by 

Technician in mechanical machining, machine designer and materials engineering student. Enthusiast for 3d print since 2011, when I started the study about it. A year later had a Prusa Mendel v2 starting to print. Today I have two printers working, building other two (for friends) and waiting more to come.

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2 thoughts on “Will your 3D-printer kill you?

  1. We just got our 3D printer, haven’t set it up yet, so it hasn’t been used. But good post here. Definitely something to keep in mind in the back of your head. Seems like more common sense to be used, but sometimes with anything electrical or mechanical, accidents do still happen. Thanks for sharing this, especially for us who are new to it.

  2. Thanks for sharing all the hazards. Something to look out for.

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