Challenges in Sustainability | 2014 | Volume 2 | Issue 1 | Pages 30‒40
DOI: 10.12924/cis2014.02010030
Research Article
Reversing the Trend of Large Scale and Centralization in
Manufacturing: The Case of Distributed Manufacturing of
Customizable 3-D-Printable Self-Adjustable Glasses
Jephias Gwamuri
1,2
, Ben T. Wittbrodt
1,2
, Nick C. Anzalone
1
, Joshua M. Pearce
1,2,3,*
1
The Michigan Tech Open Sustainability Technology (MOST) Laboratory, 601 M&M Building, 1400 Townsend
Drive, Houghton, MI 49931-1295, United States; E-Mail: [email protected] (JG), [email protected] (BTW),
[email protected] (NCA)
2
Department of Materials Science & Engineering, Michigan Technological University, 601 M&M Building, 1400
Townsend Drive, Houghton, MI 49931-1295, United States
3
Department of Electrical & Computer Engineering, Michigan Technological University, 601 M&M Building, 1400
Townsend Drive, Houghton, MI 49931-1295, United States
* Corresponding Author: E-Mail: [email protected]; Tel.: +1 9064871466
Submitted: 29. May 2014 | In revised form: 22. August 2014 | Accepted: 22. October 2014 |
Published: 12 December 2014
Abstract: Although the trend in manufacturing has been towards centralization to leverage
economies of scale, the recent rapid technical development of open-source 3-D printers enables
low-cost distributed bespoke production. This paper explores the potential advantages of a
distributed manufacturing model of high-value products by investigating the application of 3-D
printing to self-refraction eyeglasses. A series of parametric 3-D printable designs is developed,
fabricated and tested to overcome limitations identified with mass-manufactured self-correcting
eyeglasses designed for the developing world's poor. By utilizing 3-D printable self-adjustable
glasses, communities not only gain access to far more diversity in product design, as the glasses
can be customized for the individual, but 3-D printing also offers the potential for significant cost
reductions. The results show that distributed manufacturing with open-source 3-D printing can
empower developing world communities through the ability to print less expensive and customized
self-adjusting eyeglasses. This offers the potential to displace both centrally manufactured
conventional and self-adjusting glasses while completely eliminating the costs of the conventional
optics correction experience, including those of highly-trained optometrists and ophthalmologists
and their associated equipment. Although, this study only analyzed a single product, it is clear that
other products would benefit from the same approach in isolated regions of the developing world.
Keywords: additive layer manufacturing; development; distributed manufacturing; eye care;
glasses; 3-D printing
© 2014 by the authors; licensee Librello, Switzerland. This open access article was published
under a Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/).
1. Introduction
The history of mass production predates the industrial
revolution and was initially motivated by the need to
equip large armies with standardized weapons, but by
the end of the 19th century the production of large
amounts of standardized products on assembly lines
became widespread and central to economics [1‒3].
The benefits of large-scale manufacturing (or flow
production) are well established and include reduction
in costs due to the economies of scale from: i) bulk
purchasing of materials, supplies, and components
through long-term contracts; ii) technological advan-
tages of returns to scale in the production function,
such as lower embodied energy during manufacturing
of a given product because of scale; iii) favorable
financing in terms of interest, access to capital and a
variety of financial instruments; iv) marketing and v)
increased specialization of employees and managers
[4‒6]. These advantages have created a general trend
towards large-scale manufacturing in low-labor cost
countries, especially for inexpensive plastic products
[7,8].
Centralized and mass manufactured goods are
often still unaffordable to remote communities of the
developing world because of proportionally large dis-
tribution and transportation costs [9]. These trans-
portation costs have a concomitant embodied energy
and environmental impact of transportation that can
be substantial [10]. Centralized manufacturing, thus is
deficient in two fronts; cost in the developing world
and environmental impact. A sustainable manufac-
turing system with optimized value calls for a broader
and more holistic view than lowest unit cost of pro-
duction and points to the potential for distributed
manufacturing systems encompassing engineering-
management aspects, economic and technical issues,
environmental drivers and social implications [11,12].
Until recently there was no technology capable of
providing the necessary low costs and the ability to be
distributed to isolated regions.
3-D printing offers a novel form of localized and
customized production and is an emerging 21st cen-
tury innovation platform for promoting distributed
manufacturing systems [13‒18]. The technological
development of additive manufacturing with 3-D print-
ers has been substantial [15,16], which has benefited
many industries; however, the costs of 3-D printers
have historically been too high to be feasible for
distributed or home-based manufacturing [19]. Re-
cently, several open-source (OS) models of commer-
cial rapid prototypes have been developed [19], which
offer an alternative model of low-cost production. The
most successful of these is the self-replicating rapid
prototype (RepRap), which can be built from 3-D
printed parts, open-source electronics, and common
hardware for about $500 [20,21]. Using computer
aided design (CAD) customized (shapes and designs)
prototypes can be produced quickly and economically
[22] and there is evidence the RepRap can fabricate
products less expensively than conventional manufac-
turing [23]. Distributed manufacturing using low-cost
open-source 3-D printers has been shown to generally
have the potential of reducing the environmental
impact, in particular for plastic products [14‒17,24] as
the nature of 3-D printing allows for the minimization
of production waste while maximizing material util-
ization [19,25,26]. Furthermore, distributed manufac-
turing in the form of open-source appropriate 3-D
printing technology, combined with distributed gener-
ation (solar photovoltaic powered 3-D printers), has the
potential to alleviate poverty in impoverished rural
communities in the developing world [18].
This paper explores the potential advantages of a
distributed manufacturing model of high-value prod-
ucts by investigating eyeglasses, which are currently
only mass-manufactured for the reasons detailed
above. Specifically, this paper reports on a case study
of 3-D printable self-adjustable glasses by first review-
ing the potential market for low-cost corrective glass-
es and then the limitations of centrally mass-manu-
factured self-adjustable glasses. Then a series of pa-
rametric 3-D printable designs is developed to over-
come each of the identified limitations as a proof of
concept. The results are analyzed for this case study
and conclusions are drawn about the potential rever-
sal of the manufacturing trend of centralization.
2. Case Study
The World Health Organization (WHO) estimates that
globally about 314 million people are visually im-
paired, of whom 45 million are blind [27]. The WHO
predicts that 80% of all visual impairment is avoidable
(can be prevented or cured). The global distribution of
avoidable blindness based on the population in each
of the WHO regions is: South East Asian 28%,
Western Pacific 26%, African 16.6%, Eastern Mediter-
ranean 10%, American 9.6%, and European 9.6%
[27]. With almost 90% of blind and visually impaired
people living in low- and middle-income countries,
including some of the world's poorest communities,
access to eye care is often unavailable [27,28].
Globally 153 million people over 5 years of age are
visually impaired as a result of uncorrected refractive
errors (URE) [29].
Conventional approaches to correcting URE are
firmly rooted in the health-care sector and involve
having an eye care professional perform an eye exam-
ination to determine the general health of the eye and
whether eyeglasses are required to improve vision
[30]. Correcting URE requires both specialized
complex equipment and professional eye specialists—
ophthalmologists, optometrists/refractionists and opti-
cians—to implement effectively. However, access to
eye care and hence eyeglasses is severely limited in
the developing world due to an acute lack of profes-
sionals and financial resources to provide adequate
31
eye care services. For some cases in Africa: South
Africa has approximately 2400 eye care practitioners
servicing a population of roughly 47 million people
[30] a ratio of approximately 1:20,000 whilst in Ghana
the ratio of trained eye care professionals to members
of the public is 1:200,000 [31,32] and approximately
1:1,000,000 for the case of Ethiopia [30]. These ratios
are far less than the WHO recommended standard for
2010 of one refractionist per 100,000 population [27].
The African WHO region with 70.5 million estimated
cases of vision impairment due to uncorrected re-
fraction errors have a total of 4,985 existing functional
clinical refractionist and thus requires an additional
10,138 [33]. Similarly, the South-east Asia region
(196.2 million visual impairment cases) has 12,415
existing functional refractionist requiring an additional
21,651 [33]. Using a conventional approach this would
require over $2,000 million for training the additional
personnel and establishing new refraction care facilities
over a 5 year period in Africa, and over $3,450 million
for South-east Asia for the same period of time [33]. A
full functional practice requires clinical refractive
equipment, ocular health screening equipment, oph-
thalmic dispensing equipment and accounting and
business equipment as well as the cost of start-up
stock [33]. The Digital Refraction Systems alone can
cost well in excess of $33,000 and ophthalmic dis-
pensing equipment prices can be well over $10,000
[34]. Therefore, to establish a facility with basic
equipment can cost over $100,000. Automated re-
fraction requires access to expensive machines, which
must be adequately maintained and calibrated and
are mostly unsuitable for remote off-the grid com-
munities and hence not a viable option. The ratio of
ready-made to custom-made spectacles can be as-
sumed to be 20 to 80, which is in line with expec-
tations in the developed world [33,35]. Current
market prices for ready-made prescription eyeglasses
range from less than $7 online to over $1,000 from
the optometrist [36]. This eyeglass price is currently
beyond the budget of many developing world com-
munities whose cost of living is less than a $1.25 per
day. According to the World Bank report, more than
1.22 billion people in the developing world are living
below this extreme poverty baseline [37].
The general steps in the provision of refraction
services [27] can be summarized as in Figure 1.
A potential solution to this problem is self-refraction
through the use of Silver's revolutionary self-adaptive
eyeglasses [38,39]. Adjustable eyeglasses (Adspec
lens/glasses) offer the user the ability to change the
power of each adaptive lens independently to improve
vision in each eye: a process known as self-refraction,
a potential solution to the shortfall in eye care profes
Figure 1. The general steps in the provision of
refraction service.
sionals in developing countries. Self-adjusting eye
glasses thus provide a means of both measuring and
correcting refractive error in regions underserved by
eye care professionals. The use of wearer adjustable
eyeglasses solves two problems: first, it reduces the
need for measurement by a trained refractionist,
which is crucial for regions with few eye care profes-
sionals. Secondly, it offers a much simpler and far
cheaper deployment compared to a more conven-
tional approach based on lens grinding or stock optics
[30,38‒42]. Self-adjusting eyeglasses would make
vision correction accessible particularly to those in the
developing world where there is either a lack of pro-
fessionally trained optometrists and ophthalmologists,
or where the cost of traditional spectacle lenses and
professional consultation is prohibitively expensive [42].
The Adspec lens is composed of two thin circular
membranes sealed at the edges and filled with a fluid
with an index of refraction,
n,
of 1.579 [42]. The
optical power of the lens is a function of the surface
curvature, which is determined by the volume of the
fluid in between the membranes. Hence by varying
the fluid volume, the optical power of the lens can
also be varied to the desired value. Mounting two
adaptive lens on a specialized spectacle frame results
32
in an adaptive spectacles (Adspecs) [42], which offers
the user to ability to adjust the refractive power of
each lens to achieve self-refraction. The useful power
range of the lenses was reported to be −6 D to +12 D
[42]. Preliminary field trials to determine the effec-
tiveness of the Adspec lenses as a means of vision
correction were performed both in selected African
and Asian countries with promising results [38‒43].
Vision correction using self-adjusting spectacles can
be summarized as in Figure 2.
Adspecs have the potential for achieving Vision
2020; a partnership between the World Health Organ-
ization (WHO) and the International Agency for the
Prevention of Blindness (IAPB) launched in 1999 with
the twin aims of eliminating avoidable blindness by
the year 2020 and preventing the projected doubling
of avoidable visual impairment between 1990 and
2020 [27,28]. Adspec technology can be considered a
great success, however, the deployed Adspecs have
four remaining challenges: 1) the frame is highly frag-
ile, which makes it potentially inappropriate for chil-
dren and adults whose job involves manual labor (see
Figure 3), 2) the costs are too high for target com-
munities with low incomes, 3) people of different age,
gender, ethnicity and geographical locations have vari-
able widths between their eyes, which does not allow a
one-size-fits all mass manufacturing of Adspecs, and 4)
they are not aesthetically appealing and socially ac-
ceptable for many teenagers (i.e. they are not cool).
The first generation of Adspecs tended to break at the
hinge and users would use duct tape to make them
operational as seen in Figure 3a and 3b, which did not
assist with aesthetics and long term use.
Figure 2. Adaptive spectacles self-refracting
procedure.
Figure 3. a) Detail of hinge break on an Adspec lense and b) the Adspec system fixed with duct tape.
The use of open source appropriate techniques
(OSAT) [44] such as open source 3-D printing has the
potential to solve all four challenges. The first problem
can be easily overcome by varying the thickness, print-
ing density or combining different materials to achieve
the desired strength at the hinge. Second, cost reduc-
tions of up-to 95% have been demonstrated for the
open source 3-D printing of optics equipment [45] and
the 3-D printing of common household products has
been shown to be substantially lower than mass
manufacturing retail costs, neglecting additional ship-
ping and tax charges [23]. One major advantage of dis-
tributed fabrication is the ability to customize the
products to meet specific individuals' or groups' needs.
Customization provides the flexibility to selectively
fabricate eyeglass frames to each individual's taste and
eye spacing making the self-adjusting spectacles both
appealing and comfortable to wear, solving challenges
3 and 4. Youth can be afforded an opportunity to
design their own eyeglass frames according to their
preferred shape, decoration and color. The experiments
described below aim to provide a proof of concept for
overcoming these four challenges with open-source
distributed manufacturing.
3. Experimental
The entire software and hardware tool chain for the
design and fabrication of the glasses used open-
source technology, starting with a desktop computer
running Debian 7.1 (http://www.debian.org). The
glasses were designed using OpenSCAD 2013.06 [46],
33
which is a free open-source CAD scripting program that
generates and manipulates 3D objects. The glasses
were designed to be parametric by declaring variables
and then using them throughout the code. To make
changes in the design (e.g. head width), the relevant
variable is changed and the entire design is scaled
immediately and can be exported as a 3-D model in
the form of a .STL file. These files are sliced using
Cura 13.06 [47], an open-source slicing program that
converts the 3-D model into g-code. Finally, the g-
code is then printed using the open-source Repetier-
Host Linux 0.90C [48] printer controller. The glasses
were printed in polylactic acid (PLA) on a MOST
version of the open-source RepRap Prusa Mendel
[49]. This version of the RepRap uses a Bowden ex-
truder mounted to a J-head to increase print speed.
The J-head takes filament and heats it to its glass
temperature, extrudes it onto blue painter's tape to
form a shape, and then is moved up two hundred
microns to deposit the next layer of the design. In this
way, the glasses are able to be printed in under an
hour and can be customized both in design, color, fill
density and to fit each person based on head width
and the distance between pupils.
4. Results
The results of the three case study designs are shown
in Figures 4, 5 and 6. Figure 4 a) displays the 3-D
design and b) a digital photograph of self-refractive
glasses using the Adspec lenses with the first gener-
ation syringe system. The new design and community
printing capability allows for users to choose the pre-
ferred color of their glasses, to mix colors within parts
or print parts of different colors, and to customize
parts of the designs while in the community, as shown
in Figure 4b.
In order to reduce cost further while improving
aesthetics the external syringes can be replaced by a
tube and pump system so that individuals can still
adjust the lens after the initial screening. These tubes
can be printed and personalized as shown in Figure 5
a) the 3D design, b) details the customized version of
printed glasses. This design maintains the advantage
of being able to adjust the glasses as light conditions
or eye fatigue of the user change throughout the day.
This ability to make dynamic adjustments, however,
comes at the aesthetic cost of maintaining a fluid
reservoir on the wearer's glasses. Although it should
be noted it is possible to have a detachable reservoir.
There is a significant aesthetic challenge of design-
ing glasses to fit perfectly circular lenses. To overcome
this challenge at the expense of the continual adjust-
ments, the glasses were redesigned to allow for one
adjustment and then remove the syringe. In addition,
using this scheme, as can be seen in Figure 6a it is
possible to print goggles that fit the standard lenses.
This approach may not be socially acceptable in all
communities, but it provides distinct functional advan-
tages in areas prone to dust or sand storms. This de-
sign is shown in Figure 6a, image in 6b.
Figure 4. a) 3-D design of self-refractive glasses using the Adspec lenses and first generation syringe sys-
tem, b) digital photograph of the design which has a customizable component (e.g. color choice of the user).
Figure 5. a) 3-D design of self-refractive glasses using a tube and peristaltic pump with standard Adspec
lenses, b) digital photograph of the customizable component of the design.
34
All of the designs in Figures 4‒6 are developed in
OpenSCAD in a fully parametric manner so they can
be used with the Thingiverse Customizer Application.
This enables user/designers to custom fit the glasses
for themselves, as well as choose personalized aes-
thetically pleasing extras to be printed into their glass-
es without the necessity to understand CAD. The Cus-
tomizer interface is shown in Figure 7. As can be seen
in Figure 7a, user/designers can set measurements
specific to themselves, such as head width and dis-
tance between pupils. In addition, as can be seen in
Figure 7b all of the other parameters, such as the
stem length, width, thickness and dimensions around
the hinge can be adjusted to meet user preferences.
The material costs for the 3-D printable designs
shown in Figure 4‒6 are shown in Table 1. As can be
seen in Table 1 both the goggles and the standard
glasses without the syringe can be printed in under 1
hour for about one U.S. dollar using conventional
commercialized filament and U.S. electricity costs.
Figure 6. a) 3-D design of self-refractive goggles using a removable syringe clip system with standard
Adspec lenses, b) digital photograph of the design.
Figure 7. Screenshot of thingiverse customizer application used for customizing the 3D printable self-
adjusting lenses glasses for a) the front of the glasses and b) the stems.
Table 1. Mass, print time, polymer costs, and total cost of 3-D printable designs using commercial fila-
ment and standard printing procedures [23].
Part Mass (g) Print Time (min) Cost of plastic ($35/kg) Total Cost including
electricity at US ave. rates
Lens holders 15.82 28 $0.55 $0.57
Stem (each) 5.86 9 $0.21 $0.22
Stem with syringe
(each)
24.17 37 $0.85 $0.88
Goggles 29.94 53 $1.05 $1.08
Glasses 27.54 46 $0.97 $1.00
Glasses with syringe 64.16 102 $2.25 $2.32
35
5. Discussion
The technical evolution of the self-adjustable lenses
has progressed quickly, improving the quality while
reducing the cost and scaling distribution. The new
version of the Adspecs [50], which is being mass-
manufactured and distributed now, is both more aes-
thetically pleasing and solves some of the technical
deficiencies of the first generation shown in Figure 3.
5.1. Economic Costs
Cost is still the primary impediment to further scaling
and complete saturation of the need for the glasses in
the developing world. The results presented in this
study show that distributed manufacturing of some of
the components of the glasses with 3-D printers could
further assist achieving Vision 2020, as they enable
individual customizable components at the local scale
at a lower price making the self-adjusting glasses po-
tentially affordable to those living in poverty. Utilizing
distributed 3-D printing will also allow for rapid re-
placement of failed parts, since any part can be pro-
duced in under an hour. Currently, a part would need
to be ordered and time would be lost waiting for a
replacement and a potential added cost in shipping of
the new part. Using distributed 3D printing methods
also offers greater flexibility in the choice of materials
with desired properties and characteristics on the indi-
vidual scale. The flexibility of open-source 3-D printers
in materials selection also offers the potential to reduce
the costs further. As can be seen in Table 1 the primary
cost is that of the plastic commercial filament. Open-
source hardware called 'Recyclebots' has already dem-
onstrated that waste plastic can be converted into
usable 3-D printing filament at a cost of $0.10/kg in
electricity at U.S. utility rates [51]. Filament costs
used in Table 1 were the average of $35/kg. Thus,
this approach has the potential to reduce the costs
shown in Table 1 to under a single U.S. penny for any
design, essentially overcoming the cost barrier and
making distributed production far less expensive than
centralized manufacturing.
5.2. Limitations of the Approach
There are, however, several limitations to the pro-
posed technology. This approach is currently limited
by the state of development of open-source 3-D print-
ing. Although RepRaps have been shown to print in a
variety of materials, including metal [52], they are still
not yet able to print the lenses (the most critical com-
ponent of the eyeglasses) themselves. Further tech-
nical work is thus needed to be able to print all parts
of the self-refraction glasses including the optics, as
opposed to current prototypes in which only the
frames and syringe are printed.
Although cost is a crucial part of the equation for
full utilization, aesthetics is another challenge that
should not be overlooked. In this regard, further work
is needed to make printable, more aesthetically pleas-
ing or 'cool' glasses. It is hypothesized that having
students help in the design of their own glasses will
help assist in this cool-factor, but that hypothesis must
be tested by experiment.
Further work is needed in optics and 3-D printing
to be able to overcome the current limitation of the
need for circular lenses. The ability to vary lens shape
and size will make it less challenging to meet the
temporary, geographical and clique shifting socially-
acceptable requirements determined by the world's
teenagers. Finally, community capacity development
and skills appraisal workshops could assist in provid-
ing for the sustainability of the community-run/owned
3-D printing facilities.
5.3. Sustainability of Distributed Manufacturing
Although the environmental damage caused by the
manufacturing of glasses is relatively small compared
to other manufacturing sectors, this work provides a
model for improving the sustainability of manufactur-
ing not only of glasses, but also other products.
Recent studies have shown a number of benefits that
can be derived from adopting 3-D printing technol-
ogies, in particular environmental benefits [24]. The
previous study showed that with RepRap printing
using solar photovoltaic power the distributed manu-
facturing always has a lower environmental impact as
compared to conventional manufacturing of polymer
products [24]. Prototypes of solar powered 3-D print-
ing systems have already been demonstrated for
semi-mobile school-based systems, and a highly-
mobile system capable of fitting in a suitcase [53].
The latter system could be used to provide the glasses
solution to any rural school which can be accessed by
travelers bringing standard luggage. The former de-
sign is meant to become a permanent fixture at rural
schools that are not connected to the electrical grid.
Thus, the solar-powered 3-D printer can be used first
to provide glasses for the students and other com-
munity members that need them, and then it can be
used to manufacture other high-value products, such
as scientific tools (for both education and use in, for
example, medical clinics) [54]. In all these cases any
products would have a lower environmental impact
than conventionally manufactured products, even if
made locally. Realistically, most specialized products
would be manufactured in a centralized facility far
from the users and the embodied energy of trans-
portation would be substantial [55]. Thus, solar-
powered distributed manufacturing allows off-grid
rural communities to leapfrog to a more sustainable
method of production. For on-grid communities using
the same source of electric power, if the fill density of
the 3-D printed plastic product is below 79% fill
density then the environmental impact of the 3-D
printed object remains lower than conventionally
36
manufactured goods [53]. Some of the components to
the glasses do not need to be printed at 100% fill to
maintain mechanical integrity and would thus offer
this sustainability benefit as well. Many consumer
products can be printed for less than 20% fill density
[23], thus significantly improving sustainability for any
of the RepRap 3-D printers used at the schools to
fabricate other products.
However, there is a lack of data on long term field
performance of 3-D printed products. The finished
products need to undergo field evaluation for both
ruggedness and social acceptability by selected rep-
resentative samples mainly from the developing world
communities. Results from the field tests may be used
to further improve the 3-D designs for this project. In
addition, this data could be used to perform a
complete life cycle analysis of the products and com-
pared to conventionally-manufactured products. The
stability and life-time of the materials used need to be
documented and the recycling plan of old and disused
products be put in place within communities. Again,
just as the Recyclebot technology [51] would signif-
icantly improve the economics, it would have a similar
positive effect on the environmental impact [56].
Thus, broken or simply old glasses could be ground
up and turned back into 3-D printer filament to be
turned back into glasses or other products.
5.4. Lateral Scaling
The feasibility of the approach to reach a large scale
and thus millions of people all over the world is
dependent on what Rifkin calls lateral scaling [57]. In
this model of production and distribution, schools all
over the developing world will operate a RepRap 3-D
printer in relative isolation with no centralized man-
agement or logistics. The construction and mainte-
nance of RepRap printers has been demonstrated by
amateurs thousands of times all over the world. Spe-
cifically, in the U.S., teachers are trained to build and
maintain RepRaps in training workshops. A team of
two inexperienced teachers can build a delta style
RepRap printer in a day. As a true RepRap, this printer
could then be used to manufacture the specialized
plastic components of both itself and other printers to
spread the technology throughout the region. This
model could be adopted in the developing world at
very low cost points, as the RepRap knowledge
materials (for constructing, maintaining and printing)
are all available for free on line.
The data in Table 1 can be used to evaluate what
this would look like in an individual school or com-
munity with a single RepRap, which costs less than
US$500 in parts, all of which are available for pur-
chase on the Internet. With either the glasses or
goggles using approximately 30g of plastic a single
US$35 kg spool of filament would be able to correct
the vision of 33 children. If the syringes were printed
as well this would be only 15 children per kg spool.
Again, as mentioned above, if the spools were Recy-
clebot plastic, the costs would be less than $0.01 per
student served. To continue to operate the printer, the
school would need access to either the purchase of
plastic online or locally or the ability to turn waste
plastic into filament. The staff to operate the printer
could be trained in workshops or learn online for free.
Ideally, the students themselves would learn to
operate and maintain the printers as part of their
education. If the 3-D printer at a school was staffed 8
hours per day and was only used to make glasses it
could produce 8 pairs per day or 5 pairs with the
syringes per day (note: that the final print of the day
can be set up and left unattended thus effectively
increasing printing time beyond 8 hours/day). Thus,
roughly 1kg of plastic would be consumed per school
week of continuous production of glasses. Thus, if
operated for an entire year only printing glasses, a
single RepRap could produce 2,080 pairs of glasses
and Sconsume about 52 kg of plastic.
The primary application of this solution would
involve base design code (e.g the OpenSCAD scripts)
being untethered from the web and transported
manually with the 3-D printer along with the neces-
sary plastic to provide glasses given a school's popu-
lation. Thus, only the imagination of the student
population and electricity would need to be supplied.
In the case of electricity this would be provided on
site either from the grid, generators, batteries or the
previously discussed solar panels, depending on the
community's circumstances. This is a start, however,
in many locations now and in a growing number of
developing world communities, Internet access will
enable more sophisticated and rapid design browsing
and cloud-based design could play a greater role.
Cloud manufacturing, is a service oriented, customer
centric, demand driven manufacturing model [58]. It
could be used by entrepreneurs in developing world
communities (e.g. to collaborate on designs, provide
design services for sale, and even perhaps to manu-
facture items for sale in both their communities and
elsewhere [59,60]). Again, in the ideal case, these re-
venue streams could provide a return on the invest-
ment of the initial capital needed for the RepRap,
Recyclebot and filament to get started, and provide
the necessary vision correction with self-refraction
eyeglasses for students and local residents. The ad-
ditional technical skills in the community and the
ability to manufacture low-volume high-value products
in an environmentally sustainable way would be a sig-
nificant benefit. The technology discussed here is only
a single example of how open-source 3-D printers
could provide high-value products to communities in
the developing world at very little cost as there have
been many proposals for other appropriate tech-
nologies and scientific tools [18,53].
37
6. Conclusions
Although the trend in manufacturing has been
towards centralization, the technical development of
the open-source 3-D printer enables low-cost dis-
tributed bespoke production. This paper demonstrated
some of the potential advantages of a distributed
manufacturing model of high-value products by inves-
tigating self-refraction eyeglasses. By utilizing 3-D
printable self-adjustable glasses the target market not
only gains access to far more diversity in product
design, but also offers the potential for significant
costs reductions for obtaining functional corrective
glasses. The results showed that the primary cost of
the glasses could be reduced to about one dollar for a
highly customized/individualized design, which could
be printed on site in under an hour. Distributed manu-
facturing with 3-D printing can empower these com-
munities through the ability to print less expensive
and customized self-adjusting eyeglasses, displacing
conventional glasses and giving a viable option to the
world's most impoverished population who generally
cannot afford the cost of expert optics correction (e.g.
optometrist, ophthalmologist, or even conventional
lenses). Here only a single product was analyzed, but
it seems clear that other products would benefit from
the same approach and that distributed manufac-
turing can assist in sustainable development, partic-
ularly in isolated rural regions.
Acknowledgements
The authors would like to acknowledge helpful discus-
sions with J. Silver and G. Anzalone and support from
the Fulbright fellowship program.
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