Use of free CAD software for 3D printing individualized face masks based on face scans

Aim: To describe a method of digitally customizing 3D-printed face mask designs using 3D face scans and free software. Materials and methods: The procedure of creating customized face masks initially involved importing and aligning STL files of face scans and mask components in free CAD software. The imported mask described in this article is composed of three different STL files (body, filter structure, and grid). The body of the mask was then edited to fit precisely into the face scan STL by using the software's offset tool, followed by adjustments and smoothening of the surfaces of the edges. The resulting customized body of the mask plus the filter and grid STL files were exported and 3D printed with polylactic acid (PLA) filament using a fused deposition modeling (FDM) 3D printer. For the purposes of comparison, a conventional 3D-printed mask (from the original STL files, without being customized for the face scan) was also 3D printed from the original STL files. Both face masks were tested on the same two volunteers. Results: The customized 3D-printed face mask presented a higher adaptation compared with the conventional face mask. The area of facial contact matched the one digitally designed in the software. The 3D-printed grid could clip exactly into the filter, which in turn could be precisely screwed into the body of the face mask. Conclusion: Within the limitations of this technical report, the present findings suggest that customized 3D-printed face masks with enhanced adaptation can be digitally designed using face scans and free CAD software. Keywords: facial scanning, face mask, 3D printing, CAD/CAM, COVID-19