Ultrafine aerosol transient phase measurement with real-time monitoring instrument applied to cleaning process of L-Pbf machine.

Object: This research addresses different issues related to the ventilation and the aerosol concentration present in a metal additive manufacturing facility using Laser Powder Bed Fusion (L-PBF) machine. Performing air monitoring requires quantifying the emissions potentially generated in the different areas and during the different L-PBF process phases. A practical Indoor Air Quality (IAQ) assessment protocol is addressed in this research questioning the type of emissions to measure, and the way to collect them. Methods: As a measurement strategy for the airborne particles lower than 700 nm, real-time metrology discmini instruments were used (Testo, 1 L.min⁻¹, Forbach, France). The particle number concentration was assessed during three operations: (i) before cleaning the room where the L-PBF machine is located, (ii) during the cleaning phase of the room, and (iii) after the cleaning phase. Results: Without ventilation and without human activity, the background concentration level in the additive manufacturing facility was 5.10³ #/cm³ either before or after cleaning. With ventilation and without human activity, the background concentration level was decreased to 4.10³ #/cm³ before cleaning, and increased to 1.5.10⁴ #/cm³ after cleaning. Besides, human activity leads to an increase in the number of suspended particles, since they passed from 5.10³ #/cm³ to 1.9.10⁴ #/cm³. Finally, a value of 10⁵ #/cm³ was recorded on the operator during the cleaning phase and clearly, show peaks of particle number concentration. Conclusion: It was found that the local ventilation plays a role in the resuspension of particles from surfaces. Indeed, particles deposited on the floor are a source of exposure and hence the need for a clean room. The result section reinforces the necessity of wearing individual protective equipment during the maintenance and cleaning operations of a facility including L-PBF machine. [ABSTRACT FROM AUTHOR]