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Large-Scale AM for Manufacturing PPE during COVID-19
travel moves made by the printer, the largest digital design work was carried out in Autodesk
possible nozzle should be chosen, but to ensure Fusion 360. A key focus for the design was to
that the parts stay lightweight with sensible feature ensure the final shield would pass any relevant
sizes, a balance must be struck. In this case, a regulatory testing, which determined aspects such
1.8 mm nozzle was selected to achieve this required as the height of the headband being no <10 mm tall.
balance. The 1.8 mm nozzle allowed for deposition The second key design aspect was the attachment
rates of 92 mm /s, (printing a headband with <20 g points for the clear lens/visor. The visor holes
3
of PLA) while allowing for the features to be small would be made using a standard 6 mm diameter
enough for functions such as the attachment of the hole punch, and therefore, the attachment points
lens/visor. The headbands were designed with no were designed with a 5.5 mm width, distributed
overhanging sections to ensure that no material or around the front loop of the headband. Ensuring
time wasted in printing support material. The final that the printed parts were not sharp and likely to
strategy to adopt is to ensure that every move of injure the user might normally require filleting of
the print nozzle in the print job is a useful move, edges in the design, but fillets were not required
that is, all moves made are contributing to the in the computer-aided design model (Figure 3A)
deposition of material, and there are minimal as when printing with LSAM, the machine will
non-print travel moves (toolpath optimization). essentially “self-fillet” at sharp turns which can
To ensure this toolpath optimization, the design be seen in comparing the corners of the strap
was first optimized for production with only attachment points in Figure 3A and C. The final
single walls (Version 1) and then optimized for design focus was on ensuring the individual
production using “vase mode” (Version 2). In vase sections of the headband met the requirements
mode (also known as “Spiralize Outer Contour”) based on a tool diameter of 1.8 mm (parametric
throughout the print, the nozzle does not (i) travel design based on tool diameter). Therefore, the
without printing, (ii) retract, or (iii) stop extruding. front and rear sections were set to 1.8 mm thick,

3.1 Initial design (version 1) and the thicker sections of the design set to double
the extrusion width (3.6 mm), crucially with a
The initial design took inspiration from various 0.1 mm gap between the deposited tracks to allow
community-driven face shield designs available for single wall extrusion printing to happen rather
(e.g., N3DPS , Prusa , and Verkstan ) and the than the slicer infilling the region, which can be
[24]
[26]
[25]
A B

C

Figure 3. Initial design for face shield components produced using large-scale additive manufacturing,
(A) showing the computer-aided design model, (B) the Simplify3D sliced print preview, and (C) the final
printed part.

54 International Journal of Bioprinting (2020)–Volume 6, Issue 4