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.
Step 1: Safety
First, research the history of similar conditions or testing.
Research was extremely easy. A simple Google search on HCN measurement techniques along with some outreach to injection molding companies proved that this has indeed been tested and certified safe in much larger quantities.
3D Printing is really just die-less injection molding. The plastic is heated and forced to go where we desire. It cools and we have a part. So, the injection molding specialist are a good place to start. Contacting a major injection molding company in the eastern US, we were able to get the Industry Standard on injection molding safety and hard measurement of HCN with Nylon specifically. For Nylon, the industry goes by what is known as "The Barns report". This is a full up actual real time HCN testing of a injection molding machine running at 270C with 100's of pounds of material. The resulting HCN measurement was less than 1ppm, so we assumed with a tiny amount of Nylon, we were pretty safe. However, we were also going to do some "cumulative testing" where we all but seal up a specimen and heat it to extremes of 400C. More on that later.
So we're about to build a tester to test for hazardous gasses. And in doing so, we will intentionally create a worse case 3D Printer condition to force the generation of these gasses. What precautions should we take?
- No Bystanders - This is not something you do while a bunch of folks are in the next room eating lunch. Alert everyone in the building you're going to generate hazardous gasses.
- Dead Man switch - Well, not really, but you need to be able to turn heater temperature "OFF" outside of the danger area.
- Remote Visual - If while performing the test, you reach the OSHA Limit, you are to immediately leave the room to seek clean air. To understand if you can return, you can use a WIFI connected video camera pointed at the sensor.
- Ability to vent the room remotely. - If extremes happen, and someone does not get to leave from collapse or they have been overcome, you must be able to quickly vent the room to allow safety personnel access.
- Clean up - At low temperatures(78F) , HCN gas can liquefy on surfaces. After each test, you must wash off/spray off any surfaces that will be used for the next test as HCN can linger. In addition, you must wear typical nitrile gloves to keep from absorbing HCN through contact that has accumulated on cool surfaces.
- Have a smoke detector as you never know.
- Location was a garage with no other inhabitants.
- The Heater cartridge was on an extension cord that looped 100' from the garage.
- We had a WIFI enabled video camera on the test setup including the HCN sensor.
- We had a 130 cfm vent in the top of the garage and the power garage door remote.
- We used a power sprayer for clean up and just sprayed water. No other chemicals.
- We had a smoke detector and fire extinguisher.
If for whatever reason you suspect that your sensor may not be calibrated or working correctly, there are two additional early warning alarms you can use.
Bugs, yep bugs. HCN is considered a great bug killer as bug's will literally drop out of flight if they encounter anything above about 1.8ppm of HCN.
- The odor of almonds. This is in the literature and sounded a bit odd, but we are now believers as we got a whiff while testing trimmer line at elevated temperatures. We were reading spikes at about 0.6 - 1.0ppm when we detected this odor.
This testing may be performed by experienced, skilled users, at their own risk. to the fullest extent permissible by the applicable law. taulman and taulman3D hereby disclaim any and all responsibility, risk, liability and damages arising out of death or personal injury resulting from any testing defined or described.
NOTICE: HCN is considered lethal at >30ppm
This testing was performed by the taulman3D group. taulman3D.com is now a vendor of new Nylon based 3D Printing materials.