Evaluation of nanoparticle exposure during Wire Arc Additive Manufacturing (WAAM) processes

Wire Arc Additive Manufacturing (WAAM) is an advanced layer-by-layer metal printing technology that builds three-dimensional components layer by layer by melting a metal wire using an electric arc. While it is well established that high-temperature metal melting results in the emission of metal and metal oxide nanoparticles, limited data is currently available for WAAM due to the relative novelty of the process. This study investigates nanoparticle emissions in a laboratory environment where the WAAM system is enclosed within a closed box during the production phase. Measurements were conducted across four processes using AlSi5 and S700 feedstocks under both standard and non-ventilated conditions. The results show a significant release of incidental nanoparticles in all the processes during the arc activation, with average concentrations ranging from 105 to 106 n/cm3 and diameters between 15 and 22 nm. Concentrations declined rapidly during inter-cooling intervals and after the process concluded. Moreover, daily exposure assessment scenarios demonstrate that, if the WAAM system is fully enclosed during production, average exposure levels remain below the available reference values (i.e. 20,000 and 40,000 n/cm3 for high and low-density materials respectively). In contrast, when operators remain close to the WAAM system throughout during the production phase, the exposure levels can exceed the reference values by 12 % to 1.8 times for S700 and by 3–5 times for AlSi5, depending on the distance. These findings highlight the critical importance of properly installing the WAAM system to ensure effective control of operator exposure to incidentally released nanoparticles.