*2.1. Facility, Operation Conditions and Materials*

This study was conducted in an organization that uses Selective Laser Melting (SLM) technology for metal additive manufacturing. The SLM printer is located in a room dedicated to prototyping, with approximately 85 m<sup>2</sup> and 3 m in height. On the data collection day, no other equipment besides the printer was operating.

The printing process consists in the deposition of layers of a metal powder, usually 20 to 70 microns depending on materials, followed by the application of an infrared laser light scan (1064 nm) of 250 W that melts the powder to reproduce a three-dimensional part, previously defined in a CAD program. The material used was a nitrogen gas atomized spherical powder for additive manufacturing: Stainless steel 316L, with particle size between 20 and 53 μm. Stainless steel 316L is an alloy of iron (>75%) and chromium (≈17%) which also contains nickel (≈12.5%), molybdenum (≈2.5%) and other elements in less significant amount. In this case study, 59.15 cm<sup>3</sup> of this powder were used during the printing process but the final part only had 0.35 cm3 (approximately 0.59%).

In addition to the initial preparation for printing (which includes CAD design and filling the powder in the printer), the worker's tasks can be divided into 3 distinct phases, as described in Table 1.


**Table 1.** Description of the tasks under study.

Data gathering included a sample of powder before and after the printing process, technical and material safety data sheets of the powder, information on operation conditions and on-site measurements.
