Control of Particulate Material Emission during 3D Printing

Abstract

Objective: The three dimensional (3D) printer based on fused deposition modeling (FDM) technology is the most popular, due to inexpensive and easy handling. In spite of increasing popularity of 3D printers, people may overlook the possibility of the effect of 3D printing on health by 3D printing. According to recent studies, pollutants such as nanoparticles (<100 nm) and hazardous volatile organic compounds (VOCs) are emitted during 3D printing. Various thermoplastics can be used as feed materials, whereas previous studies evaluated the emitted pollutants using only PLA and ABS filament. Further, there is no specific attempt to prevent or reduce the pollutants emitted during 3D printing. This study aims to evaluate the particle emission characteristics under the two different temperature conditions for extruder and heating bed with seven different filament materials and attempts to design filter based control methods reducing the particles emitted during 3D printing. Methods: The total number concentrations of airborne particles were measured before, during, and after 3D printing using scanning mobility particle sizer (SMPS) and optical particle sizer (OPS) in an exposure chamber. Polycarbonate filters (PC) were used for the field emission scanning electron microscope (FE-SEM) for morphological properties. The 3D printer was operated under the manufacturer recommended set and consistent temperature set with various thermoplastic materials (acrylonitrile-butadiene-styrene (ABS), poly lactic acid (PLA), polyvinyl alcohol (PVA), high impact polystyrene (HIPS), nylon and laywood). The temporal particle emission rate (#/min) was calculated by equations considering the particle concentration (#/cc). Emission rate based on time (#/min) and mass of filament used (#/g) were also estimated by equations. The eight different control methods based on filters were devised to reduce particle emission from 3D printing and conducted in identical procedure as mentioned above. Results: The FDM 3D printer with all the thermoplastic filaments examined in this study (ABS, PLA, PVA, laywood, HIPS and nylon) emit nanoparticles dominantly under both the condition of manufacturer recommended set and consistent temperature set during 3D printing. The highest nanoparticle emission rates under the condition of manufacturer recommended set were 3.26×〖10〗^11#/min and 1.72×〖10〗^12 #/g with HIPS filaments, whereas the lowest nanoparticle emission rates were 3.18×〖10〗^8 #/min and 1.32×〖10〗^9 #/g with PLA filament. Accordingly, extruder temperature was higher, in adjusting consistent temperature set, nanoparticles were emitted at least one order of magnitude more than the condition of manufacturer recommended set for all filament materials. The emission rate of all materials examined under the condition of consistent temperature set were over 6.67 ×〖10〗^10 #/min. In the experiments for control method, sealing tape was applied to confirm the effectiveness of enclosure. It showed a substantial effect, 74.38% of removal efficiency for ABS2 filament under the manufacturer recommended set. Then various kinds of filters were attached to the ventilation hole for removing nanoparticles. The highest removal efficiency of nanoparticles was 99.95% with HEPA filter and over 90% with other filters using ABS2 filament, except the combination of the electret and antibacterial filter which showed 76.04%, similar to no use of filter. To verify the removal efficiency in the highest concentration under the manufacturer recommended set, the HIPS filament was used as the supplying filament, and, it was the most effective method which had enclosure and attached HEPA filter on the ventilation outlet hole. The most effective method showed 99.95% of removal efficiency, regardless of nanoparticles emitted, about 20 times higher (10,776 #/cc for ABS2 vs 209,451 #/cc for HIPS). Conclusion: In this study, the particles emitted during 3D printing for all seven filament materials were primarily nanoparticles. The emission of nanoparticles was high at the high temperature of the filament extruder. The enclosure could reduce more than 70% of nanoparticle emission during 3D printing. Nanoparticle emission could be reduced more than 99.95% in case HEPA filter was attached to the ventilation outlet hole after enclosure in the 3D printer. Therefore, it is necessary to use the 3D printer with as low extruder temperature as possible and supply the filaments which emit less particles to cut off at the source in 3D printing. And also an enclosed type of 3D printer with a ventilation fan should be used to which is attached the filter specialized to remove nanoparticles.