And, what exactly is "safe" anyway..?
If we eliminate the obvious, the fact that the belts and motors can pinch a finger as well as a heater block operating at 200+c will definitely burn you, we are left with the one unknown. That is of any hazardous fumes and odors that may be emitted by heating the plastics. We not only can't see these gasses, but most of us don't have a device at hand to make a measurement.
The intent of this DIY is to explain how to build a test apparatus to determine the safety of the material you are using to print your parts. Of course in doing so, we were able to measure and report on various common matereials.
If you just want an answer to the question "Is 3D Printing Safe" without reading the excruciating details, you're in luck.
"Yes" Based on our measurements using the world Safety Authorities (OSHA NIOSH ACGIH) Limits, 3D Printing is safe.
There was NO measured HCN from "3D Printing ABS" based materials at specified temperatures.
There was NO measured HCN from "3D Printing Nylon" based material at specified temperatures.
There was 0.1ppm of HCN while printing with a "Non-3D Printing" material (Trimmer Line)
Even in our worst case testing in an enclosed 12" cube at 420C (788F) for 10 min the maximum reading was 1ppm, again, trimmer line. The OSHA safe limit is 4.7ppm.
Quick Q and A
Did you find any items of note?
- We found that before the threshold was reached, the plastics became "unprintable" and would halt/jam the printer.
- There is a lot of naturally occurring HCN. You will probably encounter more HCN at an outdoor marshmallow campfire than we measured in our testing. Due to it's shear quantity as opposed to the small quantity we print, burning wood creates a lot of HCN.
- Again, our testing shows no HCN measured from 3D Printing materials at correct temperatures.
What gas would make 3D Printing unsafe?
An excessive amount of Hydrogen Cyanide (HCN) - A gas emitted by plastics when they are set on fire or breach pyrolysis.
And what is an excessive amount of HCN?
The international (OSHA NIOSH ACGIH) maximum allowable exposure to HCN is 4.7ppm
So? How much HCN did you measure while actually printing?
3D Printing ABS from various 3D Printing material suppliers in China, the EU and US = None
3D Printing Nylon from taulman3D 3D Printing material supplier in the US = None
Two brands of Trimmer or weed-whacker Line mfg in the US = .1ppm
Where did you get the 3D Printing material?
Defined 3D Printing Material -
ABS1 = China - A
ABS2 = China - B
ABS3 = EU
ABS4 = US
Nylon1 = US
Nylon2 = US
Non 3D Printing Material -
Trimmer1 = US
Trimmer2 = US
What did you use to measure the HCN?
Industrial Scientific Corporation T-82 Single Gas Monitor
Calibrated HCN Sensor
Certified calibration 1 day before testing
Certificate of calibration
Certified by UL, CSA, CE
What was your absolute highest reading?
Trimmer line "A" at 220c+ = 0.6ppm -1.0ppm in a semi-sealed enclosure (12" x 12" x 24") for 10 min
This is a "cumulative test" as the gas is allowed to accumulate in the enclosure, thus it's concentration in ppm is higher.
This is NOT a printing test, but one of several tests done to answer cumulative concentration questions.
Today, most 3D Printers use modular power supplies. Either re-purposed ATX (Computer PS) or enclosed wall power units, such as used by laptop computers. These are already UL listed and tested. Most of these power supplies don't exceed 24 volts, including power to the Hot-End.
Again, there are obvious safety concerns with respect to motors and belts, pulleys and or threaded rods. However, once we see these components in operation, we know to use a bit of caution and not stick our fingers in the moving parts.
There are a few hot components we need to be aware of.
- Stepper motors - These can get hot, but usually not hot enough to burn you. Most motors have an attached fan to keep them cool so as to last longer as heat damages the motors bearing surface over time.
- Power supply - These are covered units, but as they dissipate heat we need to make sure they have access to ventilation, i.e. don't block the little cooling holes and replace air filters when needed.
- Build table - These are the platform we actually print onto. They are usually heated to a temperature that will burn you. Almost all of these are vividly marked in some manner warning of "HOT" and "Do Not Touch". This is an actual UL requirement if the printer is certified.
- Hot-End or Heater block - This is the component where the plastic is melted and flows from a small opening/nozzle. This will be very hot. Between 180C (356F) and 275C (527F). Again, this will not just burn you, but mark you for life. Recently, you may have noticed that some 3D Printers have started to ship with brackets, or shields around the Hot-Ends. And in some cases, a completely enclosed printer where access is only through a door or lid. This comes from various UL and CSA requirements for finished goods where rules to protect the consumer come in to play. As of yet, 3D Printer kits have not been required to meet a lot of the same rules.
While most of us have tape measures and wrenches to make mechanical measurements/adjustments, volt meters to make electrical readings and temperature sensors to measure hot parts, almost none of us have unique gas detection equipment to detect gasses emitted by printing. And because we are changing the state (heating and melting) of plastics, they will emit fumes and odors.
3D Printing Measurement History
We can't say that no one has made this specific measurement prior to now, just that we were not able to find any information on-line or through contacts.