mixer shea butter

8/10/2019 Mixer Shea Butter

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Design of a manually operated mixing machine forShea Butter applications

ENGR 481 - Senior Design

Final Report

Sponsors:

Shea Yeleen International Inc.Mr. Larry Matthews

Faculty Advisor:

Dr. Camille George

Team Members:

Amber BeckNick DalbecJames Zoss

School of EngineeringUniversity of St. Thomas

May 2005


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Abstract

The women in Mali, North Africa lack the efficient tools and education to develop a

better means of processing Shea butter products. The current processes are physicallyexhausting and time demanding, taking several hours to complete. Women consumetheir products as well as sell them at the local markets. Shea butter is becominginternationally known as a skin care product used for moisturizing. In order to helpAfrican women establish fair-trade Shea Yeleen International, a non-profit organization,was founded. This project seeks to develop a better means of mixing using a manuallyoperated machine. After thoroughly researching, designing and experimenting, a finalmachine was developed optimizing the mixing process. The mixing time wassuccessfully reduced form several hours to thirty minutes. All other engineering andcustomer design requirements were met. Through the success of our design, Shea YeleenInternational will be able to disseminate the machine and hopefully help fight poverty in

Africa.


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Table of Contents

I. Team Member Assignments1

II. Background of Shea Yeleen International.2

III. Project Background.3

IV. Mission Statement4

V. Customer and Engineering Requirements5

VI. Project Management...8

VII. Product Cost Analysis...10

VIII. Engineering Budget...12

IX. Concept Generation...14

X. Prototype Progression...17

XI. Manufacturability..22

XII. Testing Results...22

XIII. Temperature and Water Dependence..26

XIV. Final Design Evaluation........28

XV. Conclusions.29

XVI. References...30

XVII. Appendices

Appendix A: Gantt Chart

Appendix B: Blade Concept Analysis

Appendix C: Scale Reduction Testing

Appendix D: Power Source Concept Analysis

Appendix E: Procedure/Assembly

Appendix F: CAD Drawings


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I. Team Member Assignments

Amber Beck: Team Leader

Midterm Presentation, Project Management, Gantt chart, Testing procedures, Final Paper

Nick Dalbec

Manufacturing Prototype, Bill of Materials, Project Budget, Cost Analysis, Testing

Procedures

James Zoss

Computer Animated Design (CAD), Testing Procedures, Manufacturing, Prototype

Evaluation


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II. Background of Shea Yeleen International

Shea Yeleen International (SYI) is a nonprofit organization that was founded in

March 2003 by Rahama Wright

1

. The organization hopes to encourage community

development and the possibility for fair trade of shea butter products. In Africa, Miss

Wright engaged a small group of educated Malians to explore the possibilities of

marketing shea butter. Local women cooperatives have been developed with a mission to

create a sustainable business. The central focus of SYI is to assist West African women

with obtaining the necessary tools and education to produce shea products. These

products can then be sold internationally and help the women fight against poverty.


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III. Project Background

Malian women use shea butter for many daily applications as well as a source of

income. Their current production method is physically demanding and lacks in quality

and efficiency. Without standard steps to follow or guidelines for procedure, the current

process is difficult to replicate. After collecting nuts the women must clean and de-shell

them. The nuts are then roasted, ground into a paste, and kneaded. The oils separate out

through kneading, and the paste is then filtered. The oil portion is left out to cool over

night resulting in the final product. The focus of this project is to improve the current

Malian kneading process. On average, kneading by hand takes hours to complete2.

From a social perspective, the Malian communities are very poor. The average

Malian makes less than two dollars a day, and this income must cover the cost of

medicine, food, and clothing for an entire family. Women work very hard in these

communities to maintain the health of their families. Culturally, the Shea nuts belong to

the women, thus making Shea butter an area where women can gain more economic

freedom3.


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IV. Mission Statement

Our goal is to design a Shea butter mixer that will benefit the Mali community by

reducing the Shea butter mixing time and increasing production of Shea butter for fair-

trade.


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V. Customer and Engineering Requirements

1 Materials obtainable in Mali

2 Non-corrosive materials

3 Safe to use

4 Easy to operate and clean

5 Simple to manufacture and maintain

6 Cost effective

7 Produce quality product

Table 1: Customer Requirements

1 Cost less than $100

2 Fabrication reasonable for local craftsmen

3 Open container for easy access

4 Material of blade/container must be non-corrosive

5 Material of power source parts must be plastic, steel, or wood

6 No complex transmission or gear setup

7 Easy to clean parts

8 No sharp edges or rotating parts exposed

Table 2: Engineering Requirements


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the current processing. Current mixing processes take several hours to complete; the new

machine will reduce this time as much as possible.

Groups of Malian women will form cooperatives where they can have access to

the mixing machine. The machine shall produce enough Shea butter products for

personal consumption and to sell in local and international markets, thus providing an

opportunity to earn a regular source of income.

The mixer will improve oil extraction and increase the product inventory for the

local Malian women. This project should have a positive impact economically and

financially on the people of Mali. There will be culturally appropriate training materials

in French and Malian languages supplied along with the final design. Illustrations will

accompany the training materials to show operation techniques. The final design will be

sent to local Shea Yeleen International contacts to continue implementation of the

machine. Table 3 shows how the engineering requirements relate to the customer

requirements.


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Table 3: Customer Requirements vs. Engineering Specifications Matrix (QFD)

VI. Project Management

Tasks for the project were divided equally among the three team members.

Manufacturing was completed by Nick and James, while Amber managed the tasks and

deadlines of the project. Many of the experiments were conducted with at least two

members present and each team member was responsible for taking observations and

developing design ideas. Regular team meetings were held to discuss shortcomings and

progress of the project. A Gantt chart can be found in Appendix A displaying the

individual task assignments and deadlines. This chart was used to guide the team and

assure timely completion of the project. Each experiment provided insight for the project

and so Gantt chart was updated regularly with new tasks to accomplish.

Engineering Requirements

Costles

stha

n$100

Fabri

catio

nreasonable

forlo

calcraftsm

en

Material

s:Pla

stico

rStee

lContain

er/Bla

de

Material

s:Pla

stic,Ste

elorWood

powe

rsource

part

Nosharp

edgese

xposed

Easy

tocleanp

arts

Open

containe

rforeasya

ccess

Nocomplex

transmission

orgear

set-u

p

CustomerRequirements

Local Materials X X X

Non-Corrosive X

Safe X

Easy to Use X X X X

Simple Design X X X X

Cost Effective XQuality Control X

CustomerRequirements


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Preliminary ResearchExperimenting

& DesignPrototype

Testing in

MaliFinal Design

Project Selection Shea NutsBlade ConceptTesting

Horizontal HandCrank List of Supplies

Address DesignIssues

Meet TeamMembers

Current ProductionMethods

Miniature ScaleModel Testing

Hand BicycleDesign Travel to Mali Modify

Meet with AdvisorOther Methods ofOil Extraction Container Testing

Hand Drill PowerSource

Observed CurrentProcesses

Send outProcedures toliaisons

Set-Up Schedule Containers Phase Test On-Site Design Testing in Village

Contact Liaisons Blade DesignsTemperatureAnalysis Final Design Adjust Machine

Power Source &

Transmission

Purchase New

Parts

Shea ButterJournal Testing in Village

Nigerian Thesis User Survey

Substitute Product

Table 4: Work Breakdown Structure


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VII. Product Cost Analysis

Bill of Materials in United States

Material Total Price of Material ($)

4"x 4" x 10' Pine Post 1 pc $9.19 ea. $9.192"x 12" x 10' Pine Board 1 pc $13.95 ea. $13.951/4" Threaded Rod 7 ft $0.23 /ft $1.615/8" Washers 15 pcs $0.06 ea. $0.901/4" Wing Nuts 13 pcs $0.13 ea. $1.692.75" Screws 20 pcs $0.05 ea. $1.001/20" Stainless Steel Sheet Metal 2 lbs $2.00 /lb $4.005/8" Round Stock Stainless Steel 1 lbs $2.00 /lb $2.003/8" Round Stock Mild Steel 1 lbs $0.40 /lb $0.405/8" Bronze Oil Impregnated Bushing 2 pcs $1.56 ea. $3.123/8" Bronze Oil Impregnated Bushing 2 pcs $0.47 ea. $0.94

3/8" Pulley (3 39/32" pitch) 1 pc $6.52 ea. $6.525/8" Pulley (1 29/32" pitch) 1 pc $3.62 ea. $3.6260" V-Belt 3L 1 pc $6.58 ea. $6.581/2" PVC Pipe (Handle) 1 pc $0.15 ea. $0.15Container 1 pc $10.00 ea. $10.00

$65.67Total Material Cost Per Unit ($)

Quantity Price/Unit

Table 5: Bill of Materials (US)

The overall cost per unit is under $70 US, which meets the design requirement of

$100 US.


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The cost in Mali is under $50, but will vary depending on the village and

availability of parts.

Table 6: Bill of Materials (Mali)

On-site we were able to redesign and develop the machine using the tools and

materials locally available. Through purchasing items locally we were able to get an

accurate cost analysis of the machine and it was evident that our new design could be

manufactured in Mali.

While purchasing materials in Mali, it was apparent that items like wood, steel,

pulleys and belts were easily obtainable. These items were common and cost efficient.

Bill of Materials in Mali, Africa

Material Total Price of Material ($)

8cm x 8cm x 1m 3 pcs $1.70 ea. $5.108cm x 30cm x1m 3 pcs $3.20 ea. $9.601/4" Threaded Rod 2 m $1.80 /m $3.605/8" Washers 15 pcs $0.04 ea. $0.601/4" Wing Nuts 13 pcs $0.15 ea. $1.952.75" Screws 20 pcs $0.07 ea. $1.401/20" Stainless Steel Sheet Metal 2 lbs $3.00 /lb $6.005/8" Round Stock Stainless Steel 1 lbs $3.00 /lb $3.003/8" Round Stock Mild Steel 1 lbs $0.40 /lb $0.405/8" Bronze Oil Impregnated Bushing 2 pcs $1.00 ea. $2.003/8" Bronze Oil Impregnated Bushing 2 pcs $0.50 ea. $1.003/8" Pulley (3 39/32" pitch) 1 pc $2.10 ea. $2.10

5/8" Pulley (1 29/32" pitch) 1 pc $2.10 ea. $2.1060" V-Belt 3L 1 pc $5.00 ea. $5.001/2" PVC Pipe (Handle) 1 pc $0.40 ea. $0.40Container 1 pc $3.00 ea. $3.00

$47.25

Labor TotalFabrication of Blades $1.05Welding Blades $0.75Fabrication of Handle $0.45

$2.25

$49.50

Total Material Cost Per Unit ($)

Quantity Price/Unit

Hrs0.350.250.15

$US/hr$3.00$3.00$3.00

Total Labor Cost per Unit ($)

TOTAL COST PER COMPLETE UNIT ($)


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Stainless steel was more difficult to find and more expensive to purchase, however

Professor Ouane at the Ecole Nationale dIngenieurs assured us that stainless steel can be

obtained at an affordable price. He also helped establish prices for non-regular items (i.e.

bushings, pulleys, belts, stainless steel). The design requirements of cost, non-corrosive

materials and safety were all met using the items discussed above.

The fabrication shop rates varied depending on if you were in the village or in the

city. The local craftsman determined his own price depending on the complexity and

demand for his labor. In the village, a local craftsman charged only 500CFA (about

$1.00) for welding, grinding, and re-work required of the blades and shaft for 20 minutes

of his time. Therefore, an average shop rate of $3/hr in Mali, Africa was calculated.

VIII. Engineering Budget

1st Semester

Hours Cost

LaborAssociate Engineering Hours 440 $11,000.00Consulting Engineering Hours 35 $1,750.00

MaterialsTesting Medium $15.00Laboratory Equipment Use $100.00Steel $10.00Fabrication $25.00

$12,900.00First Semester Total


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2nd Semester and J -term (excludes trip)

Hours CostLaborAssociate Engineering Hours 390 $9,750.00Consulting Engineering Hours 25 $1,250.00

MaterialsPulleys, Belts, Bushings $15.00Screws, threaded rod, nuts washers $5.00Lumber $63.00Stainless Steel, Mild Steel $97.00Container $10.00

$11,190.00Second Semester Total

Hours CostLaborAssociate Engineering Hours (in Africa) 252 $6,300.00Consulting Engineering Hours (in Africa) 80 $4,000.00Trip Planning Assoicate hours 60 $1,500.00Trip Planning Consulting hours 25 $1,250.00Plane Tickets, Hotels, Meals, transportation $10,000.00Out of Pocket expense $1,500.00

$24,550.00

$48,640.00Accumulated Project Total :

Trip Costs

Total Trip Expenses

Table 7: Budget

The first semester budget is broken down into two major parts: labor and

materials. The team consisted of four associated engineers, putting in ten hours a week

for eleven weeks. The salary was calculated at $25 per hour based on a $50,000 entry-

level engineer. Consulting hours consisted of Dr. George, Harry Gebbens, and contacts

from Shea Yeleen International. Their salary was estimated at $100,000 per year at $50

per hour.


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The materials purchased first semester consisted of parts for fabrication and shop

tools used. All other parts and components used for experimenting were accounted for.

The total cost for first semester was: $12,900.

The second semester and J-term budget consisted of everything except the March

trip to Africa. Three associate engineers remained on the team after first semester.

During J-term only two associates were able to work on prototype development and

testing. Associate hours for J-term and second semester totaled 252 hours. The total cost

for second semester and J-term was: $11,190.

The trip to Mali contributed to almost half of our budget. Three engineers and

one consulting engineer (Dr. George) were considered as part of the trip cost (tickets,

hotels, food) at $2,500 per person. Other expenditures were accounted for such as: travel

agencies, booking fees, materials, translators and preparations for departure. A $500

travel fee paid by each of the three associated engineers was also included in the budget

report. The total cost for the trip to Mali was: $24,550. The project total throughout the

entire year totaled to $48,640.

IX. Concept Generation

The method of mixing used by women in Mali is to mix by hand. Most often the

container holding the paste is placed on the ground, and women stand over the bucket and

bend at the waste. Not only is mixing by hand tiresome and time consuming, but the

bending can cause strain on the back, making the process only suitable for younger

women. In order to ensure an efficient development of all aspects of the project the


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mixer was separated into three main components: blades, container, and power

source/transmission.

Blade Concept Designs

Proof of Concept Testing

The first step in selecting a blade design was proof of concept testing. For this,

five different blade designs were constructed and tested by a visual inspection of mixing

food coloring into a mixture of flour and water. From this testing, the helical blade

inspired by an auger and the hollow blade inspired by kitchen mixers were found to be

inadequate. More information about blade selection can be found in Appendix B.

Scale Reduction Testing

During the months of January and February, more testing was performed. Scale

models of the three best performing blade designs from the proof of concept testing were

produced. This was done so that they could be tested with the limited supply of actual

shea paste that was available. After testing, it was found that the asymmetrical blades

were able to extract oil most efficiently. More information on scale reduction testing can

be found in Appendix C.

Power Source Concepts

There were two main power source concepts tested. A discussion of other power

source possibilities can be found in Appendix D.


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Hand Crank

The hand crank consists of an offset vertical shaft directly connected to the blade

via a horizontal link. It is a simple and effective way of rotating the shaft. One problem

is that it can be quite difficult to rotate the shaft.

Hand Bicycle

This idea was originally derived from a standard bicycle drive system. The

concept was adapted to a hand powered style to accommodate for the preferred range of

motion for the Malian women. The hand bicycle concept is composed of two handles on

opposite sides that rotate horizontally around a fixed point. A gear or pulley is placed

between these handles for the accompanying transmission of power. A gear ratio can

easily be applied to reduce the amount of energy required to turn the crank. This power

source can be manufactured simply through then bending of round bar. A person could

use one or both handles for manual power, or two people could use the opposing handle

to combine their efforts.

Transmission Concepts

The first concept was to use a set of bevel gears to transfer rotation of two shafts.

This concept can be seen in many mechanical systems. This idea was mainly thought of

by the examination of differentials in automobiles. Bevel gears are a very effective way

of transferring power however, they can also be costly. This concept was discarded.

The next transmission idea was that of a twisted belt around two perpendicular

shafts. This was an idea seen by the examination of vacuum cleaner transmission. Since


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this concept is an effective way to transfer motion while still being cost effective, it was

selected to be used as a transmission.

Container Concepts

The concepts for a container came down to two different options; a plastic bucket

or a hand made bucket. One successful shea butter processing method in Ghana uses a

hexagonal container for shea butter mixing. Our contact claims that it is the hexagonal

shape of the container that is vital for the oil extraction4. The container is custom-made

out of stainless steel in order remain non-corrosive. Stainless steel is expensive and to

manufacture a hand made container would not be as simple as buying a plastic one.

Therefore, after results of testing revealed that that oil could in fact be extracted without

the hexagonal design, we selected the plastic container. This is explained more

thoroughly in the Testing section and in Appendix C.

X. Prototype Progression

From the different experiments and proof of concept studies performed, the

plastic bucket, angled asymmetrical blades, and a horizontal bicycle style hand crank

with a twisted belt transmission were the options chosen for our machine prototype.

Materials selected for the initial prototype were based upon the implied availability and

manufacturing capabilities in Africa. The machine developed on-site in Mali used

materials and manufacturing techniques found in local markets.

Failure with our second prototype during the initial testing phase in Mali proved

to be greatly beneficial for our product development.


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Prototype Progression:

1stPrototype

Qualities:

Proof of concept machine.

Hand crank on 5 gallon bucket.

Steel and wood frame.

Problems:

Difficult to turn.

No access to paste inside bucket.

2nd

Prototype

Qualities:

Wood beam on top of 5 gallon

bucket.

Slotted wood crank frame.

Two sided bicycle style hand

crank.

Twisted belt.

Bucket and crank frame separate from each other.


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Problems:

Very unstable.

Difficult to keep belt in tension.

Difficult to access contents of bucket.

Crank tended to come out of slots.

Wood beam was not anchored to bucket.

3rd

Prototype

Qualities:

One piece frame design.

Wider plastic bucket.

Threaded bar through wood plank to

anchor bucket.

Two pieces of metal on either side of

threaded bar.

One-handed crank.

Longer, wider blades.

Crank positioned by a hole in a vertical post.

Problems:

Belt slipped after time.

Somewhat difficult to turn.

Two piece metal tension plates difficult to get into place.


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More suited for a left handed person.

Bare metal crank uncomfortable on hand.

4th

Prototype

Qualities:

Addition of tensioning thread bar and block.

Problems:

Somewhat difficult to turn.

Two piece tension plates difficult to get

into place.

More suited for left handed person.

Bare metal crank uncomfortable on hand.

Tension bar and block requires a vice grip

to fully tension.

5th

Prototype

Qualities:

Larger pulley on crank.

Brass bushings placed in crank post.

Plastic handle added to crank.

Crank moved to opposite side.

Tension thread bar incorporated into shaft beam.


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Single piece of metal with slot used for vertical tension bars.

Drilled a hole in the post for tensioning bar and added a wing nut and washer

eliminating the need for a vice grip.

Problems:

To produce the slot in the single piece of metal used to clamp down the container

may be difficult.


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XI. Manufacturability

With limited availability of shop tools in the village, the final design of the

mixing machine requires minimal tools necessary for assembly. Wing-nuts are used to

reduce the need for special tools in assembling the machine. All other parts are either

hand-drilled or hand-tightened further eliminating the need for expensive tools. Screws

are used to secure wood fixtures and a screw-driver set was left in the village to ensure

the local Malians would have adequate tools for manufacturing the machine. Cutting

wood, drilling holes and alignment of parts were all done effortlessly by the local

Malians.

Welding will be completed by the local craftsmen. Working with the craftsman in

Mali, it was evident that his capabilities and skills were exceptional for the work required

to manufacture the blade assembly. Any failures or problems resulting from daily use of

the machine will be easily maintained and fixed in Mali.

XII. Testing Results

The objective of traveling to Mali was to test the mixer under real applications

and use. It was also critical to obtain user feedback to make adjustments and

improvements based on their comments. The first testing result was beneficial for the

group, providing us with crucial feedback from the local Malians. Our second and third

tests proved successful.


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The machine design for the second test was significantly improved. The design

was simple, the range of motion was comfortable and the features of a hand crank were

more desirable. Successful results were obtained after just 58 minutes of mixing the

paste.

Table 9: Observations of the re-designed mixer in Mali.

Tim e Pas te Ap p earan ce

05

10

Ad de d lo ts of water ,approxim ately 2:1 water to pasteratio. Belt kept slipping, addeda support board to k eep belt intension. Paste felt sticky, likegum.

20

25

3035 W ater drop test45 Foam present, lighter in color50

55Ad de d water to crea te be tte rseparation

96 degrees F

Did not take temp. readings of paste,

previous testing show ed little to nosignificant changes in paste temp.

Tested w ith 10 lbs. of paste

Design 2

Afr ic a

Lots of oil and water splashed onto wo od,

could result in bacteria. Mach ine seem smuch faster than working by hand.Requested the handle be placed on theright side of post.

Oily and more viscouscompared to test one

Bamako Pro to type

58W hite foam was

extracted!

Can hear a thunking sound aspaste hits wall of container.Paste started to feel oily andslide against the container.

Test

Location

Environment

Conditions (in shade)

User Comments

Quantity of Shea

Paste (approx.)


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The third test was conducted back at St. Thomas with our final redesigned

machine based off comments made by the local woman. After simulating the Malian

environment in a room at 85 degrees Fahrenheit, successful oil extraction was obtained

after just 30minutes of mixing.

Table 3: Observations of the final design testing in the United States

Time Paste Appearance

05

10

20

25

Added more water

Design 3

United States

85 degrees F

5 pounds of nuts were crushed andresulted in close to 3 pounds of paste

Final Design

Warm water was added to thepaste approximately 1:1 ratiopaste to water. From Nigerianstudies and experience in

Africa we knew to add warmwater (94 degrees) Results ofNigerian studies showed 3parts water, but after addingone part to our paste we

decided it would be best not to

begin with that much. Therewas not a lot of paste to startwith. After 10 minutes pastetemp. was 84.6

African water drip test, WECOULD SEE OIL!!!

We predict they will like the more

comfortable handle height, position onpost and handle material. By using alarger pulley less force is required foruse.

30Successful whitefoam extraction!

Test

Location

Environment

Conditions (in shade)

User Comments

Quantity of Shea

Paste (approx.)


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XIII. Temperature and Water Dependence

The viscosity of shea paste is highly dependant on the surrounding ambient

temperature. A variety of tests were conducted to determine what temperature was

optimal for working with shea paste. We attempted to regulate temperature using a water

bath and space heaters; however it was difficult to maintain consistency throughout the

experiment. In order to determine the temperature the paste would experience a change

in state, a phase experiment was conducted. Results showed that the paste was

completely solid around 60 degrees Fahrenheit and did not change to be completely

liquid until around 120 degrees Fahrenheit. The conclusion was then that shea paste has

a large range where it is not completely a solid or liquid.

Shea Paste Phase Chart

50

60

70

80

90

100

110

120

130

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Time (Seconds)

Temperature(F)

Chart 1: A phase diagram of shea paste.


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Attempts to determine the optimal testing temperature were unsuccessful. Using

information from www.weather.com, we found that average temperatures in Mali were

around 90 degrees Fahrenheit and decided to test in the temperature range from 85 95

degrees5. While in Mali, temperature was recorded regularly and it was then determined

that the temperature of the paste does not change much during processing. The average

temperature determined on-site in the shade was 98 degrees Fahrenheit and the average

temperature of well water added to the paste was 86 degrees.

Through experimenting at the Institue dEconomie (IER) observations of

processing was noted. The addition of refrigerated water was added to the paste in small

quantities. The experiment was not successful and while cleaning out the machine it was

observed that the paste had begun solidifying on the container, shaft and blades.

Therefore, when working with shea paste, cold water (below 70 degrees Fahrenheit)

should not be added. The temperature of the water being added affects the chemical

reaction taking place in the mixing process.

Upon returning to the United States a Nigerian Thesis on shea butter had arrived.

This proved useful in determining the optimal amount of water to add when extracting oil

from shea paste. The results of experiments discussed stated that three parts water to one

part paste is most advantageous6. After the oil begins to separate, more water can be

added without concern. Our experiments with the final design of the mixing machine

supported these results.


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XIV. Final Design Evaluation

The cost of the mixer meets the requirement at approximately $50.00 (in Mali).

All parts in contact with shea paste are made of stainless steel or plastic.

Disassembly is easy because it requires no tools.

o Wing nuts can be unscrewed allowing clamps to be removed easily.

o Shaft and shaft post are removed in one piece separating easily from

bucket. This allows for the easy cleaning of the mixer.

The mixer can accommodate many different sized containers. The use of a wide

container allows for easy access to the paste.

Rotating the crank at approximately 60 rpm causes oil extraction at approximately

30 minutes.

Oil extraction ratio of 3:1 was maintained using the mixer.

Operation of the mixer can be done by one woman.

o There is an option of sitting or standing while using the machine.

Tensioning the belt only requires the turning of a wing nut.

Benefits/Features

The final design was intended to be flexible and easy to use. The most complex piece

of the design is the blades, which consists of three different lengths of stainless steel, all

8mm wide. They are welded onto the shaft at a 45 degree angle. Fabrication of the blade

design is within the production capabilities of villages. Other parts for the machine are

available in local markets. The design is adjustable so that different container sizes can

be used. Since the setup/disassembly of the mixer requires no tools, it is easy to use and


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clean. Mixing time is greatly reduced and the larger bucket allows for greater batch sizes

of shea butter to be produced.

XV. Conclusions

Through research and experimentation the Mali Mixer team was able to develop a

successful prototype. Using feedback from the Malian women was vital for the final

design. User comfort was kept in mind for ease of use, range of motion, and the location

of the power source. The manually powered machine met all customer and engineering

design requirements. Using the mixer, the women in Mali were able to produce twice as

much shea butter with little to no physical strain. The final design was able to extract oil

in 30 minutes, greatly reducing the average mixing time. With reduced mixing time,

reduced physical strain and an increase in batch size, production of shea butter products

will increase.

The Mali Mixer team is optimistic for the future of this project. Shea Yeleen

International (SYI) will be able to disseminate the machine and educate the local village

women in how to form cooperatives and establish fair-trade. Using the assembly

instructions and drawings provided, SYI contacts will be able to teach people how to

build, maintain, and optimize production from the machine. With the increase of shea

butter production in the villages, women will be able to sell their products and create

more income for themselves. As SYI begins working with more and more women in

Mali, the establishment of fair-trade and the fight against poverty will be set in motion.


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XVI. References

1. Wright, Rahama; Shea Yeleen International. 280 Madison Avenue,

Suite 912, New York, NY 10016. [email protected]

(2004).

2. http://sheabutter.web.aplus.net/id10.html(Oct. 2004).

3. http://www.un.org/ecosocdev/geninfo/afrec/vol15no4/154shea.htm

(Oct. 2004).

4. Akuete, Eugenia; [email protected](Dec. 2004).

5. http://www.weather.com(Jan. 2005).

6. Olaoye, Joshua. Oil Recovery Process From Shea Butter Seed

Through Modified Clarification. Thesis: April 1994.

7. Olaoye, J.O. and Babatunde O.O.; Development and Testing of a

Milled Shea Nut Mixer. Journal Food Science Technology, Vol. 38

N. 5 pp. 471-475, 2001.


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XVII. Appendices

Appendix A: Gantt Chart

Located on the next 4 pages.


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Appendix B: Blade Concept Analysis

Six blade concepts were considered and compared based on given design

requirements. Five of the six blades were constructed and tested. The sixth design was

the hollow blade with inserts; it was evaluated based on extrapolated assumptions.

In addition to design requirements given by the client, engineering requirements

were added to evaluate overall performance. Each requirement was weighted according

to its contribution to the blade design. Mixing efficiency was weighted at 22.5% and was

the main focus of determination followed by cost, safety, and manufacturability.

Each blade was scored in all the design requirement categories, with a score of

five considered the best option. The data was then compiled to make the blade selection.

Two of the blade designs were close in ranking. The solid asymmetrical and solid

symmetrical were rated at 4.88 and 4.775 respectively. Based on this analysis, the design

of the solid asymmetrical and symmetrical blades will be the main focus for future

prototype designs.

WeightPercent

SolidAsymmetrical

SolidSymmetrical

AngledBlades

Holloww/Inserts

HollowAsymmetrical

Helical

Description Scale

Manufacturing Ability 17 5 5 3 2 3 1

Measure by timeand tools necessaryto manufacture 5 Easy -> 1 Difficult

Cost 18.5 5 5 4 5 5 4ater a ost an

Labor involved 5 Cheap -> 1 Costly

Torque Required 12 4 5 4 2 2 4

Measure the time ittakes to mixefficeintly

5 Easy (less torque) ->1 Hard more torque)

Mixing Efficiency 22.5 5 4 3 3 2 5ow ong t too to

mix thoroughly oroug y -> ot

Thorough

Maintenance Required 12.5 5 5 4 4 4 3How easy is it toclean parts?

5 Little to nonemaintenance- > 1High Maintenance

Safety 17.5 5 5 4 5 5 3How dangerous arethe parts involved?

5 good -> 1 no good(sharp edges)

Total: 100 29 29 22 21 21 20Weighted Total: 4.88 4.775 3.605 3.555 3.5 3.415

Table 1: Blade Design Resul ts


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The blades have the most influence in fulfilling the requirements of efficiency and

product quality in our design. During the mixing process, the blades are in direct contact

with the Shea paste. As the blades mix water into the paste, they induce the separation of

oil.

The first step in developing blade proof of concepts was to research different

types of blades from existing technology. One project liaison is a Peace Corps volunteer

named Rahama Wright. Rahama lived in Mali for over three years and while there she

produced a video of the traditional production of Shea Butter. The information obtained

from Rahama provided a foundation for research and helped aid in defining the customer

requirements.

The video of the Malian women processing the shea paste provided a blueprint for

the mechanical mixer. In the current process, the women sit hunched over mixing in a

manner similar to kneading bread dough. Their hands are immersed in the viscous Shea

paste. Occasionally water gets added to the paste, interrupting the mixing process.

Figure 1 depicts the traditional kneading process in Mali.

Figure 1: Malian women kneading the Shea


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With the motion of the Malian womens hand movement in mind, other mixing

methods were looked into for similarities. The proven mixing systems that were

researched were an ice cream mixer and a butter churn. Ice cream mixers gently mix to

keep the fluid content homogenized. This motion prevents large ice crystals from

forming while gradually extracting heat and freezing the cream. The project liaison

suggested an old-fashioned butter churn because the Malians are familiar with the motion

required for churning. Through research it was found that butter churns are simple in

design and provide agitation to dairy fluids. One butter churn was found online that had

a solid paddle blade mounted on a vertical shaft with a hand crank. This blade design

was also observed in a few of the ice cream makers and seemed simple to recreate.

Industrial mixer manufacturers were also researched. One industrial mixer for

viscous fluids employed an auger blade that rotated axially. It was diagonally mounted

on an arm that rotated the auger along side of the container. All industrial mixers were

extremely expensive and complex, most with multi-axial blades. Even though the

complexity of these mixers was out of production capabilities the auger idea seemed like

a plausible concept. It not only provided transaxial fluid movement but also axial.

Another group of industrial mixers had a propeller design with blades mounted

diagonally onto their rotating shafts. As with the helical blade, this design induced an

axial flow of fluid like an airplane propeller.

Kitchen mixers were also researched. Most electrical kitchen mixers

manufactured by companies such as KitchenAid, CuisineArt, and Bosch came with three

different blades: a whisk, a dough hook, and a heart shaped hollow blade. Whisks are

designed for non-viscous fluids such as eggs. However, Shea paste is too thick and


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viscous to mix with a whisk. The dough hook was considered but it did not fit the

appropriate application. Shea Butter mixing must accomplish a range of viscosity that

starts as a thick paste and ends as a fluid. The final fluid is similar to the consistency of a

milk shake. The heart shaped hollow blade, which was made for medium viscosity

ranges like pancake dough, seemed applicable to the project. This blade looked like an

outline of a leaf made out of bent extruded bar stock.

With further research, the ideas from different types of mixers were put together

and modified to the project. As a result, five proof of concept blades were fabricated:

helical, solid symmetrical, solid asymmetrical, angled, and the hollow asymmetrical

blade.

All proof of concept blades were made out of welded steel because it proved

quick to assemble and made a durable product. All blades have a solid 16mm diameter

shaft that fits into the mounting apparatus in the same manner.

Helical Blade

This blade proof of concept was created to simulate an auger. The helical blade

(Figure 2-A) has 15 individual whisk blades, each 117mm long and 6.4mm diameter.

They were then welded onto the main shaft in a helical formation with approximately an

inch of separation.

Figure 2-A: Helical Blade


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Solid Symmetrical and Asymmetrical Blades

These blade proof of concepts were created to simulate the solid paddle design of

a butter churn. The solid symmetrical blade (Figure 2-B) and asymmetrical blade (Figure

2-C) both have four individual 123mm x 76mm x 2.75 thick steel sheet metal blades

which are welded axially onto the main shaft.

Angled Blade

This blade proof of concept was created to model the industrial mixer propeller

design. The angled blade (Figure 2-D) used three individual blades that measured

102mm x 76mm x 2.75mm thick steel sheet metal first welded onto rebar 101mm in

length by 13.6mm diameter. They were then welded onto the main shaft.

Figure 2-B:Symmetrical Blade

Figure 2-C:Asymmetrical Blade

Figure 2-D: Angled Blade


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Hollow Blade

This blade proof of concept was created to model blade designs of kitchen mixers.

The hollow blade (Figure 2-E) was fabricated with welded sections of rebar resulting in a

U-shape design 123mm on length and 115mm in height. Four of these U-shaped rebar

were then welded asymmetrically onto the main shaft.

Testing Procedures

Shea paste is necessary for testing the mixing process of our machine. This Nut is

only found in West Africa and is very difficult to get overseas. In order to begin proof of

concept testing, a substitute product was required.

Through research it was determined that peanut butter would be the best substitute

for Shea paste. The process of making peanut butter is very similar to making Shea

Butter. The main difference is that when making peanut butter the process stops at the

grinding stages. The goal is to keep the oils in peanut butter, not extract them. One of

the project contacts who had worked with Shea Butter also said that the viscosity of

peanut butter felt the most like that of Shea paste. The problem with peanut butter is that

it is very expensive.

Figure 2-E: Hollow Blade


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In order to keep the cost down, it was decided to use a mixture of flour and water

for the proof of concept testing. The testing looked for differences in the mixing based

on blade design. While it was understood that viscosity would play a factor in the final

product, the group chose to simply examine the differences in mixing with the current

procedure in order to get a better understanding of mixing processes in general.

The testing of the blades was first done by creating a mixture of flour and water.

The mixture used was a ratio of 4.52 kg of flour with 7.25 L of water. The flour and

water was then mixed by kneading until a uniform consistency was achieved. This

mixture had a similar consistency to that of pancake batter. A consistency resembling

that of peanut butter (viscosity of 1290 kg/m3) was originally desired to simulate the Shea

paste. Density figures were unavailable for Shea paste. Because flour has an ability to

compact, an accurate density was difficult to obtain. The final mixture ratio of flour and

water was determined by inspection.


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Appendix C: Scale Reduction Testing

During the months of January and February, scaled down versions of blade

designs were created and tested using actual shea paste. It was decided that the scale

should be reduced because of the limited supply of shea paste in our possession. In order

to eliminate a number of variables, an electric mixer set at 60 rpm was used as a power

source. The container containing the shea paste was set in a water bath so that the

temperature could be raised to the proper level and be consistent for each test. A

hexagonal container was constructed and tested along with a circular container. The

hexagonal container was manufactured to determine if the container shape was vital to oil

extraction as stated by a contact in Ghana4. Both circular and hexagonal containers were

used to determine if the shape was a key factor for oil extraction. A space heater was

also set up near the mixer to increase the ambient air temperature around the test.

Testing Procedure

Required Equipment

1. Container ( circular or hexagonal)

2. 250g of Shea Paste

3. Water bath basin

4. 2 stands

5. General Signal Lightnin mixer

6. Poly Science water heater

7. blade shaft

8. 800 ml beaker


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9. 1 tablespoon measuring spoon

10.Thermometer or thermal couple

11.Space heater

Procedure

1. Place Poly Science water heater into water bath filled with water.

2. Set water heater to heat to 35 C.

3. Place Shea paste into container, and place container into water bath.

4. Attach blade shaft to mixer and place shaft into container so that the end of

the shaft is centered and not touching the bottom of the container, then fasten

mixer to stand.

5. Place space heater about 2 feet away from water bath set-up and turn on to

800 watts setting and a medium temperature.

6. Allow paste to heat to 27 C

7. Set mixer to mix at 60 rpm

8. Add 4 tablespoons of water to paste, and begin mixing; record paste

temperature, air temp, and wattage being used by the mixer.

9. Add 1 tablespoon of water to paste every minute for 3 minutes.

10.At t = 10 minutes, add 2 tablespoons of water, record data.

11.At t = 15 minutes, add 1 tablespoon of water, record data.

12.At t = 20 minutes, add 2 tablespoons of water, record data.

13.Monitor paste and add 1 to 2 tablespoons of water as needed. Record data

every 5 minutes.


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14.Remove oil from top as needed and place into separate container.

From this testing, we were able to see that oil separation was able to occur in

circular containers, and that the asymmetric angled bladed extracted this oil in the

shortest amount of time.

Figure 1: Experiment setup

Figure 2: Circular container showing oil extraction


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Figure 3: Hexagonal container used


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Appendix D: Power Source Concept Analysis

Treadle

The idea of a treadle came from the examination of how certain older sewing

machines and spinning wheels operate. A vertical motion of a foot pedal rotates a

flywheel that in turns rotates a shaft. This rotation would have to be transferred through

the use of bevel gears. The most appealing aspect of this power system is the flywheel.

This rotating mass creates a larger moment of inertia. This would allow the shaft to

rotate longer with less effort because more energy is stored. Since this requires a large

mass to act as a flywheel that could become expensive and cumbersome, this idea was

eliminated.

Electric and Combustion Engine

The electric motor and combustion engine are obviously the power sources that

require the least amount of effort to be applied by the user. However, these options were

eliminated from consideration early in the design phase. One design requirement is that

the final product cost less than $100 US. These motors are often expensive, and would

end up consuming a very large portion of the construction budget.

There are also environmental concerns associated with both of these options.

Combustion engines require the use of petroleum products that are much too costly for

the average village woman. Gasoline is priced roughly around four dollars a gallon,

which is twice the daily income of the average village woman. This also requires that

women continue to incur costs even after the machine has been built. Electric motors

require a source of electricity. Most electricity in Mali comes from diesel generators,

which as has been stated, can be expensive to operate over time. Automotive batteries


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are prevalent, however there is no method for recycling them, and their disposal often

leads to the contamination of ground water.

A concept hand crank was made using steel tubing, wood, copper bushings and a

length of galvanized pipe. A handle made of flat steel plate and a round steel bar was

connected to the galvanized pipe. The galvanized pipe was bored out to allow it to fit

over the blade shaft. A hole was drilled into the pipe as well as each shaft and the shaft

and pipe were attached using a pin. This allowed for the rotation of the handle to be

transmitted to the blade shaft. This concept hand crank can be seen in Figure 1.

Once a uniform consistency was achieved, a measurement of the required force to

turn each blade design was found through the use of spring force scales. Multiplying this

figure by the distance of the center of the handle to the center of the blade shaft gave the

amount of torque required to turn the shaft. Each blade was tested in the flour mixture

for a total time of 15 minutes. During the first minute of mixing, a bottle of food coloring

was added to the mixture. Observations regarding the mixtures color, texture, and

consistency were made after every minute of mixing. When the color and texture had

become uniform, the mixture was considered to be evenly mixed. Force measurements

were also made at several points throughout mixing to confirm that the amount of torque

Figure 1: Hand Crank Design


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required to turn the blade was consistent. Five blade designs were tested using this

method.

Test Results

Based off of test procedures and methods used, calculations were made to

determine the best results of the power source alternatives. Four power sources were

considered and compared based on given design requirements. The hand crank was the

only power source constructed due to time constraints and current manufacturability.

The power source alternatives were evaluated using the design requirements given

by the client. In addition, engineering requirements were added to evaluate overall

performance. Each one was weighted according to its contribution as a power source.

Torque required was our main focus, weighted at 22.5%, followed by cost, reliability,

manufacturability and maintenance required.

Each power source was scored based on its performance in each of design

requirement fields. A score of five was the best option available for the given category.

The data was compiled and the power source design rankings were compared. Three

designs stood out as plausible options. The hand crank, hand bicycle, and treadle

receiving 3.47, 3.395, and 3.36 respectively were top choices. The treadle design was

ruled out due to inconsistent information from several primary sources as to availability

of materials. The two other designs will be pursued in future prototypes.

The primary concern when choosing a power source is the transmission required

to rotate a shaft for the blades. A 90-degree rotational shift from one plane to another

could prove prohibitively expensive. A beveled gear could make the transformation but


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would also add to the cost of the design. Further investigation for a twisted v-belt to

make a similar transformation is being explored. This can be seen in Figure 2.

WeightPercent

HandCrank

HandBicycle

Treadle

Battery/Combustion

Description Scale

Manufacturing Abilit y 13.5 4 3 3 5easure y me an oos

necessary to manufacture 5 Easy -> 1 Difficult

Cost 16.5 4 4 3 1Material Cost and Labor

involved 5 Cheap -> 1 Costly

Torque Required 22.5 2 3 4 5Measure the time it takes to

mix efficiently5 Easy (less torque) -> 1 Hard

more torque)

Maintenance Required 13.5 4 3 3 2 How easy is it to clean parts?5 Little to none maintenance- > 1

High Maintenance

Safety 9.5 4 4 3 1How dangerous are the partsinvolved?

5 good -> 1 no good (movingparts)

Reliability 13.5 5 4 4 2 Life expectancy of unit? 5 Very Reliable -> 1 Replace

Functionality 11 2 3 3 5 Usefulness/fatigue 5 Practical -> 1 Impractical

Total: 100 25 24 23 21

Weighted Total: 3.47 3.395 3.36 3.15

Figure 2: Power Source Results


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Appendix E: Procedure/Assembly

MATERIALS

Wood/Lumber

*Length of wood is important but other dimensions are approximate

5cm x 30cm 8cm x 8cm

1 5cm x 30cm x 100cm (length)

1 - 5cm x 30cm x 200cm (length)

4 8cm x 8cm x 30cm (length)



Nuts/Washers/Screws/Threaded Rod


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Threaded rod

*The Diameter of Rod Determines Wing-Nut size, washer size, holes to drill

4 - 0.635cm diameter threaded rod 50cm (length)

1 0.635cm diameter threaded rod 30cm (length)

Wing Nuts

*Must thread on threaded rod

14 Wing nuts

Washers

*Needs to slide over the threaded rod

14 Washers outside Diameter 3cm


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Screws

*Must be long enough secure pieces of wood together

20 Screws 7cm (length)

Metal

*Diameter of Shaft DETERMINES bushings and pulleys to purchase!

Stainless steel

1 Sheet approximately 35cm x 30cm square approximately 0.15cm thick

1 Shaft approximately 1.5cm Diameter x 70cm (length)

Steel

1 Shaft approximately 1cm Diameter x 50cm (length)

2 Anchoring plates 8cm (length) by 12cm width and approximately .15cm thick


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Bushings or Bearing

*Shaft Diameter is important to match. Outside Diameter is not crucial but will need Drill

Bit to match size

2 Bushings with Shaft Diameter of 1.5cm

2 Bushing with Shaft Diameter of 1cm

TOOLS

1 Dill

1 Screw driver

1 Hammer

1 Welder

Various Drill bit Sizes


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STEPS

*Container purchased will minimally affect design. Slight modifications will need to be

made with container obtained.

Blades

3 blades will need to be cut from the stainless steel sheet metal.

1) Measure container to determine radius at the bottom, middle, and top of container.

These will determine how long your blades will be.

2) First blade will be 2cm shorter than radius at bottom of container by 8cm wide. (It

will be 2cm shorter due to width of shaft attaching it to and human error)

3) Second blade will be again 2cm shorter than middle radius of the container by

8cm wide.

4) Third blade will be 2cm shorter than top radius of container by 8cm wide.


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Next weld blades on shaft.

1) Take the shaft approximately 1.5cm Diameter x 70cm (length) and mark 6cm

from one end, 12cm from same end, and 18cm from same end.

2) Weld first blade to shaft at 6cm mark on shaft on a 45degree angle.

3) Weld second blade to shaft at 12cm mark in opposite direction on 45degree angle.

4) Weld third blade to shaft at 18cm same direction as first at 45degree angle

Handle

1) Take shaft approximately 1cm Diameter x 50cm (length) and make marks at

15cm and 35cm. Bend shaft at 15cm mark 90degrees then 90degrees opposite

direction at 35cm so it looks like:


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Post Handle

1) Take 8cm x 8cm x 100cm (length) and measure 25cm from one end and 4cm in

from side to find center of hole to drill

2) Drill a hole at mark using drill bit that is the same size as the outside diameter of

the Bushing with Shaft Diameter of 1cm

3) Press the 2 Bushing with Shaft Diameter of 1cm into the wood.

4) Slide handle through


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Top Table

1) Take the 5cm x 30cm x 100cm (length) draw a line down center of the board

2) Measure 4cm from each side of line and draw a line whole length of the board.

Again measure from the centerline 4cm PLUS the diameter of the threaded rod to

both sides of center line.

3) Find center of board and measure out the top radius of the container from the

center. Measure 2cm in from this distance and 8cm out from this distance,

creating an approximately 1cm x 10cm(length) slot. These will be your slots to

make it adjustable to containers needs.


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Container Post

1) Take the 8cm x 8cm x 100(length) and place it on top of your container. Cut it to

size but allowing 15cm over hang on one end and about 20cm on other. Find

center of container on 8cm x 8cm post and mark it.

2) Drill a hole at mark using drill bit that is the same size as the outside diameter of

the Bushing with Shaft Diameter of 1.5cm

3) Press the 2 Bushing with Shaft Diameter of 1.5cm into the wood.

4) Slide blade shaft through bushings.

5) Cut out a section of the post 2cm deep by 25cm long from the end that over hangs

the bucket by 20cm.

6) Next drill a hole 30cm deep (or as deep as you can) and the same diameter as the

threaded rod in the end of 8cm x 8cm post on the end that over hangs on the

bucket 20cm. This act as a belt tensioner later.


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Anchoring Plate

1) Cut/grind slots 0.635cm wide (size of threaded rod) in anchoring plates as

follows.

Assembly

1) Take the 5cm x 30cm x 100cm (length) board and attach with screws the four

8cm x 8cm x 30cm (length) posts to the corners.

2) Attach with screws the 5cm x 30cm x 200cm (length) board to step one as such.

3) Attach Handle post off center in front of top table with screws


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4) Attach the other 8cm x 8cm x 100cm (length) with screws and cut to appropriate

length and cut ends on angle accordingly.

5) Place container on top table centering it.

6) Take the 0.635cm diameter threaded rod 30cm (length) and put it in the hole of

the container post drilled earlier. Slide washer over end and tighten with wing nut.

(Note the tensioner will push against Handle Post. A steel plate made be needed

so threaded rod does not push too far into handle post wood.) Slide blade shaft

through bushings in post and put on top of container. Slide pulley approximately

5cm in Diameter on blade shaft and lock in place. (See CAD drawing).

7) Slide the four-threaded rods through slots on top table and around container post.

Slide anchoring plates across top of container post andthrough threaded rod to

secure container in place. Use washers as seen in drawing. Secure with wing nuts

to set in place. (See CAD drawing).

8) Slide pulley approximately 10cm in Diameter on 1cm handle shaft and attach belt.

(See CAD drawing)

9) Use tensioner to tighten belt and tighten down wing nuts on top container post

Slide plastic pipe over handle for added comfort. (See CAD drawing).


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Appendix F: CAD Drawings


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