3D Printing – Evaluating Particle Emissions of a 3D Printing Pen

3D printers and pens may emit particles and volatile substances. We have developed a method to analyze the emissions of 3D pens. Our method is simple, easy to implement and cost-effective to set up.

It can be used to characterize the particle emissions near the breathing zone of the user. This technique can also be used to analyze aerosol emissions from other sources and devices like spray products or ablation processes. Before beginning an experiment, select a 3D printing pen capable of generating temperatures greater than 200 degrees Celsius and select filaments with a 1.75 millimeter diameter, suitable for the 3D pen.

Clean the inside of a desiccator, with an inlet on one side for inserting the 3D printing pen and an outlet on the top for inserting the sampling tube. Make sure that an air inlet at the connection to the 3D pen is established. The outlet tubing should be 10 centimeters from the tip of the 3D printing pen to mimic the distance between the user's head and the emission source.

10 minutes before starting the 3D pen aerosol emission measurement, switch on the CPC and SNPs online measurement instruments and pre-load the 3D pen with the filament of interest. When the pen has cooled attach a HEPA filter to the SMPS inlet and run a clean check measurement with the SMPS to ensure that the SMPS is not contaminated from previous measurements. Connect the chamber outlet to the CPC inlet and use the CPC to check the concentration inside the chamber to ensure that the chamber is clean and that the experiments are running under the same conditions.

To measure 3D pen aerosol emissions, insert the preloaded and cooled down 3D pen into the chamber and make sure that the outlet tubing of the chamber is connected to the CPC. Start the computer connected to the CPC and open a new file, with a name suitable for the measurements to be taken. Make sure that the CPC flow is set to 0.3 liters per minute and measure the background concentration for 10 minutes.

At the end of the measurement, switch on the 3D pen and select the appropriate temperature for the loaded filament. When the filament temperature has been reached, start the printing process and let the 3D pen print for 15 minutes. At the end of the printing period, connect the outlet tubing to the SMPS and obtain size distribution measurements every three minutes, for the next 30 minutes.

When all of the measurements have been acquired, remove the printed filament and clean the chamber. To quantify the sample preparation by inductively coupled plasma mass spectrometry, print the filament of interest on a plastic surface to avoid contamination with metal and use a ceramic knife to cut the filament into smaller pieces. Weigh out approximately 150 milligrams of both bulk and printed filament and transfer the filament pieces into microwave vessels.

Add 1.5 milliliters of water, 3.5 milliliters of nitric acid, and one milliliter of hydrogen peroxide to each sample. Place the vessels into the microwave and heat the samples to 200 degrees Celsius, for 20 minutes. At the end of the digestion, dilute all of the filaments samples in ultrapure water, for which a high metal concentration is known or suspected, to avoid contamination of the instrument.

Then use a survey scan to determine which metals are in the samples and quantify the metal content of the specific metals using the appropriate calibration standards. As observed, higher numbers of ABS black particles are released during printing compared to printing with PLA black. Increasing the temperature during the printing of PLA, results in higher particle number concentrations, with no significant effect on the geometric mean diameter of the particles.

Printing with ABS results in high particle number concentrations and larger particles compared to printing with PLA. As expected, a clear trend in difference in the geometric mean diameter is observed between the particles emitted during printing with ABS and PLA filaments. Transmission electron microscopy imaging shows particle sizes, mostly around 50 nanometers, for PLA and almost consistently larger particles up to 100 nanometers, for ABS black.

PLA copper filaments contained copper, mostly in crystalline form as well as PLA particles. In this image, a released carbon nanotube from a PLA carbon nanotube filament is possibly observed. The release of small steel particles during the printing with a PLA steel filament and a possible agglomeration of silver aluminum flakes during printing with PLA compound with an incredibly high silver aluminum flakes amount may also be observed.

Further analysis of the aerosol by online coupling of ICPMS, short for inductively coupled plasma mass spectrometry, can facilitate the clarification of emitted methods. Our fast and cost-effective method can also be used to identify particle emissions in other areas that could benefit from aerosol characterizations.