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Large-Scale AM for Manufacturing PPE during COVID-19
Stringing is often difficult to minimize, especially sequential deposition (while less could be printed on
when using large print nozzles. When producing the bed at the same time due to print head geometry
multiple copies of the face shield parts on a single constraints), actually reduced the print time per
print bed, it was found that stringing often occurred headband (compared to parallel printing) as time is
(Figure 5B), leading to significant, sharp defects, saved in removing the travel moves within a single
and random deposits of material on certain regions layer. Other benefits of using sequential printing
of the headband piece (Figure 5C). This parallel include minimizing both the risk of a single print
print strategy also meant that “vase mode” could failure causing a whole print bed of parts to be
not be used, leading to the reintroduction of the damaged and the risk of the print material running
seam line defects caused by the layer change. The out and leaving a whole print bed of incomplete parts.
total print time for 27 headbands was 2 h 9 min The resultant print time for a headband was 3 min 20
giving a time of 4 min 47 s per headband. s per headband (1 h 30 min for 27 headbands).
Instead, a sequential production process was Overall, the production time achieved was
employed, where each part was first completed, in significantly less compared to other community
“vase mode,” before a new part was commenced and open-source face shield designs. To quantify
(Figure 5D), significantly reducing the number of the reduction in time, multiple other designs were
travel moves (red lines) during the total print. The produced on either a standard desktop 3D printer
small overall Z height of the individual parts ensured (Ultimaker 3) or the 3D Platform with the results
that the sequential deposition was achievable by shown in Table 1.
limiting potential print head collisions with parts 3.4 Mechanical testing
already produced. Switching to sequential deposition
had no significant impact on part production time To further compare the different designs and
and improved the quality of the final parts, with no ascertain their robustness, the Version 2 printed
visible defects or sharp areas requiring hand finishing on the large-scale system (3D Platform [3DP])
(Figure 5B and C). Interestingly, switching to and the Version 2 printed on a desktop system

A B C

D E F

Figure 5. (A) Toolpath preview of parallel print process with travel moves shown in red, and photos
showing a comparison of the quality of (B) multiple parts on a single build plate using parallel production
strategy with defect areas highlighted and (C) multiple defects versus (D) toolpath preview of a sequential
print process and photos of (E) multiple parts on a single build plate using sequential production strategy
showing (F) minimal defects.

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