SafeSource:
Designing a Better Safe Water Storage
System
Robin Davis
Meryl del Rosario
Joanna Natsios
Paul Saindon
CDC – Safe Water System
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Approx. 20L water vessel
Ships efficiently
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Easily carried with hands or on
head
Lid
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Tough, robust material
Nests and stacks on palate for
easy shipping
Difficult to remove
With opening large enough for
filling but small enough to
prevent contamination from
hands
Tap for dispensing—on/off/hold
All citations: www.cdc.gov/safewater/faq.htm#disinfectant
Current CDC standard water
vessel
Alternative Designs: TiO2 as
antibacterial agent
 Considered using TiO2 –based water purification system
instead of current sodium hypochlorite (SH) system. When
exposed to UV light, TiO2 exhibits bactericidal effects.
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Pros
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Tasteless
No risk of overdose
No harmful disinfection
byproducts
TiO2 photo-oxidation is
a renewable process
Purification process
integrated into vessel
SH must be kept at
pH11
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Cons
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Requires longer periods of
time for purification
Requires high surface
area to volume ratio
More costly than SH
($2.40/yr per family)
Is not more effective than
SH at killing bacteria
Last Year’s 3.082 Design
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Thermoforming
Selected Jolivert style
tap
Recommended HDPE,
but used ASB
No work on lid design
Dimple for head is
uncomfortable
Cylindrical Bucket
Square Bucket
Jolivert Tap
Planned Improvements
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Selection of ideal polymer material
Modifications to square design
Elimination of “webbing” in areas of high
curvature
Easy-to-secure, hard-to-remove lid with
ergonomic handles
3D Printing a Male Mold
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Form solid ceramic
mold from SolidWorks
design
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0.1 to 0.2 mm layers of
material
Layers composed of
binder printed into
powder
Infuse cyano-acrylate
into finished product
increase strength
Can withstand intense
heat of thermoforming
process
http://209.235.222.5/articles/03/March/products/4.jpg
Large 3D Mold Process
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The full production size is too large to create
a 3D mold from the printer.
Instead several interlocking parts will be
designed to fit together into a single mold
that is large enough to create our piece.
Thermoforming
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Process by which a
sheet of plastic is
shaped.
Has low startup cost
versus other methods
such as injection
molding.
Is meant for small or
medium scale
production.
Animation from: http://www.pmwproducts.com/animation/singlesheet.gif
Material Requirements
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Able to be thermoformed
Machinable
UV and weather resistant
Safe to drink from
Resistant to chlorine and preferably other
chemicals
Inexpensive
Material Solutions
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ABS
Polycarbonate
VHMW PE
UHMW PE
PVDF
Image from: http://www.caslsoft.com/
Comparisons
Material
Thermoformable Chemical Resistance
Weathering
Safe
Cost
ABS
Yes - Great
Avoid Gas, alcohol,
toluene
Poor UV
stability.
Unsure
Cheap
$30sheet
Polycarb
onate
Yes – Good
Avoid Methylene
Chloride, dioxane
Yes
Some
forms
Cheap
~$35
VHMW
Yes – Good
Avoid toluene, xylene
Great stability
Yes,
FDA
Mid
range
UHMW
Yes – Great
Avoid strong acids,
hydrocarbons
Yes
Yes,
FDA,
USDA
Mid
range
PVDF
Yes – Good
Avoid acetone methyl
ethyl ketones, NaOH
Great UV and
Gamma, Wet
Environment
Yes,
FDA
Highest
Data from: McMaster-Carr http://www.mcmaster.com
Project Timeline
Feb 12
Mar 1
Mar 15
Apr 2
Apr 15
May 6
1
2
3
4
5
6
7
8
9
10
1. Learn SolidWorks
6. Design mold of interlocking parts
2. Create compressive elements on
SolidWorks
7. Print 3D scale models of bucket and lid
3. 3D print compressive elements
4. Conduct compressive strength tests
5. Determine physical limits of mold
geometry
8. Thermoform scale prototypes with
various materials
9. Choose material for final bucket and lid
10. Make full-sized bucket and lid