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

, Joshua M. Pearce

1,2,3,*

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)

Department of Materials Science & Engineering, Michigan Technological University, 601 M&M Building, 1400

Townsend Drive, Houghton, MI 49931-1295, United States

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

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

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,

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

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],

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.

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

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

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].

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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