Development of a standard emission test method for the determination of particle emission from 3D printing with Fused Filament Fabrication filaments

Small commercial 3D printers enable the printing of individually designed objects. They have become increasingly popular in recent years and are being used more and more in private households, in schools and in small enterprises. One of the most widely applied 3D printing technologies in commercial printers is Fused Filament Fabrication (FFF). FFF-3D printers use thermoplastic filaments as feedstock. The plastic filament is melted in a hot nozzle and is then extruded and is deposited on a printing bed to construct a 3D object layer by layer. However, the high printing temperatures cause heat stress and partial thermal degradation of the polymeric feedstock. This can lead to formation of particles and harmful gases that are eventually released indoors. The user is therefore (unconsciously) exposed to air pollutants that is associated with increased health risk. The filament product itself largely affects the produced emission. Thus, it seems expedient to use low-emitting filament products as a preventive measure to protect consumers. By awarding an ecolabel, e.g., the well-established German ecolabel “Blauer Engel”, the user can make an informed purchase decision with regards to the potential exposure risk. A standard emission test method for testing filament products is needed for this purpose which is developed in the present work. The test method stipulates to measure the particle emissions under defined climatic conditions and air exchange rates in so-called emission test chambers. The use of different printer models as test printers is possible because of a standardized printing procedure developed in this work. A test printer always extrudes a defined filament strand at a constant rate for every filament product. Printer settings are reduced to a minimum. In addition, the printer-related emissions were systematically examined. The extruder temperature control, the printer housing, the printer built-in air filter, and heated printer components were identified as crucial factors influencing the particle emission. Important technical specifications for the qualification of test printers were elaborated in order to ensure comparability in emission tests. Furthermore, a comprehensive investigation of the emission characteristics regarding the particle number concentration and size distribution from FFF-3D printing in the size range from approx. 1 nm to 20 μm was conducted. Technical specifications for the particle measuring instruments were derived and a technically feasible instrumentation for emission testing is proposed. A draft test instruction is presented.