Particle emissions from fused deposition modeling 3D printers: Evaluation and meta-analysis

Abstract

Fused deposition modeling (FDM) 3D printers, the most popular choice among home hobbyists, have been shown to release volatile organic chemicals (VOCs) and billions of airborne particles per minute, indicating the potential for consumer inhalation exposure and consequent health risks. Publications on FDM 3D printer emissions however, contain large heterogeneity of testing methods and analytical procedures making it difficult to reach overall conclusions for particle characteristics or particle number emission rates across the field. In this publication, data were collected over the printing time from 3D printer emission studies including particle count diameters (PCDs) (nanometers), particle number concentrations (PNCs) (particles/cm³), and particle number emission rates (PNERs) (particles min^-1). Despite heterogeneity in methods, the majority of particles released were reported as ultrafine in size (i.e., <100 nm) indicating that using both acrylonitrile butadiene styrene (ABS) and poly-lactic acid (PLA) may present a risk of exposure to respirable particles. Mean PNC emitted in 3D printing tests ranged over several orders of magnitude across publications with overall means of 300,980 particles/cm³ for ABS and 65,482 particles/cm³ for PLA. Although mean PNC data were available from only 7 of the 16 papers reviewed, ABS resulted in greater particle numbers than PLA suggesting increased exposure to ultrafine particles. A linear mixed model was fitted for mean PNCs to further explore the impact of nozzle temperature and filament material. Finally, the PNER calculation method especially regarding losses, varied widely across studies, and directly impacted the PNERs reported. To strengthen direct comparability of results going forward, it is recommended that standard emissions testing protocols be developed for FDM 3D printers and particle influxes and losses be more uniformly calculated.

Keywords: ABS; Emission rate; Filament; PLA; Ultrafine.

Fig. 1.

Identification, used a key word search (3D printers, nozzle, Fused Deposition Modeling, emissions, FDM, filaments, ABS and PLA). Screening criteria involved an indication of the measurement of particulate emissions during printer operation. Eligibility criteria for studies included in the overall analysis were: (1) the study collected and analyzed emissions from an operating FDM printer using ABS or PLA filament; (2) the study provided data on size, concentration and/or emission rates of emitted particles and (3) the study was peer-reviewed. Studies included in the meta-analysiseither directly reported mean particle number concentrations for PLA and ABS polymer filaments or this value could be calculated from available data. In addition, these studies had three or more observations for both ABS and PLA.

Fig. 2.

The relationship of particle count diameter to nozzle temperature across selected studies. (Left) Contains mean particle count diameters from authors that reported these. (Right) Contains mode particle count diameter from authors that reported these. Each symbol represents a different author that an individual run was taken from.

Fig. 3.

The relationship of mean particle number concentration to nozzle temperature across selected studies. (Left) Contains mean particle number concentrations from authors that reported them. (Right) Contains peak particle number concentrations from authors that reported them. Each symbol represents a different author that an individual run was taken from.

Fig. 4.

Forest plot of mean particle number concentrations and their 95% confidence intervals left-truncated at zero. (Left) Includes mean particle number concentrations for ABS filament. (Right) Includes mean particle number concentrations for PLA filament.

Fig. 5.

The relationship of particle number emission rate to nozzle temperature across selected studies. (Left) Contains mean particle number emission rates from authors that reported them. (Right) Contains peak particle number emission rates from authors that reported them. Each symbol represents a different author that an individual run was taken from.

Fig. 6.

The relationship between the effect of different particle number emission rate calculations on three different recorded concentrations across 3D printer studies. (Upper left) The results of particle number emission rate calculations using raw data from Stefaniak et al. (2017). (Upper right) The results of particle number emission rate calculations using raw data from Zhang et al. (2017). (Bottom left) The results of emission rate calculations using raw data from Azimi et al. (2016). Each symbol and color represents a different calculation method found in Table 4. (Bottom right) A table that summarizes mean and peak values across the previous 3 figures.