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Design and AM of a medical face shield
with x , where i = 1÷10. Based on the results Thus, market research considered different types
Fi
obtained from the valuation matrix, the following of materials and their individual characteristics,
percentage values were obtained: x = 8.181%, costs, life span, recycling procedures, production
F1
x = 6.0%, x = 12.0%, x = 12.545%, x = volumes, and other particular features of the face
F2
F5
F4
F3
11.091%, x = 7.091%, x = 10.909%, x = shield and of the production process. The research
F8
F6
F7
9.455%, x = 9.455%, x = 13.273%. team selected material extrusion (MEx, also
F9 F10 referred to as Fused Deposition Modeling [FDM]
2.4 Economic dimensioning of the functions or Fused Filament Fabrication) as the primary AM
For the second step of TFA, economic process to produce the redesigned face shield. PLA
dimensioning of the functions was conducted in material was selected due to the ease of printing
accordance with thorough benchmarking in the and an advantageous cost-performance ratio.
medical device sector. Costs were estimated based Considering that singlepart weighs an average of
on Ruffo et al. (2006) and Hopkinson and Dicken’s 20 g (weight of reference products) and it can be
(2003) models [20,21] , in which they propose that manufactured in 60 min from medium grade PLA
the total cost (C) is the sum of the cost of the filament with a price of 170 monetary units per
raw materials and the indirect costs, as shown in kilogram, the total cost of manufacturing one face
equation (1). The indirect cost of hourly activities shield structure is 32.48 monetary units. Based
is shown in Table 2. on the findings of the market analysis, the total
calculated costs were assigned by a TFA specialist,
C P g M P g T (1) as presented in Table 3. Each function participates
ind
mat
in the total cost with a percentage value, noted with
where P is the price of the raw material, y , i = 1÷10. For the redesign of a face shield, the
Fi
mat
measured in monetary units per kilogram; percentage values of the functions participation in
M is the mass of the 3D printed product, the total costs are: y = 9.852%, y = 6.958%,
F2
F1
measured in kilograms; y = 13.793%, y = 15.763%, y = 10.160%,
F3
F4
F5
P cost rate, measured in monetary units/ y = 5.849%, y = 7.758%, y = 9.236%,
F8
F7
F6
ind
hours; y = 8.312%, y = 12.315%.
F9
F10
T is the total production time of one part, Economic dimensioning addresses the
measured in hours. comparison between the functions value and cost
TFA is usually applied to existing products to weightings, aimed at the identification of three
increase their value or lower their costs, through main function status: A function is too expensive
redesign strategies. In the case of the face in relation to other functions; a function is too
shield, economic dimensioning was based on expensive compared to its contribution in the
the hypothesis of evaluating the average values products’ value; a function is too expensive in
of the main characteristics, which can include relation to the existing manufacturing technical
product weight, product performance, direct and possibilities. To accurately analyze the relationship
indirect costs, and manufacturing time. After TFA between function costs and value, four diagrams
is deployed, these average values are stated as are plotted (Figure 4).
final requirements and metrics with ideal values.
2.5 Diagrams
Table 2. The indirect cost of activities. At this stage, the smallest squares method is

Activity Cost/hour (monetary units) used to plot the diagrams necessary for TFA. To
Production work/time 7.99 properly deploy the smallest squares method, the
machine following parameters need to be calculated:
Machine costs 14.78 • The regression line:
Fixed and variable costs 5.9
Administrative costs 0.41 y = axg (2)

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