CHAPTER ONE
1.0 INTRODUCTION
In view of the rapidly increasing population of the country, the majority of the population
depends on the end product of pressed cassava, which is fried into “Garri” as a staple food. In
order to alleviate the difficulties encountered in the local garri pressing. It is necessary to design
and construct a power screw cassava presser which will press cassava mash to an acceptable
level of dryness before frying operation.
The hydraulic presser are pressure exerting machine tools. They can be classified into three
principal categories as hydraulic pressure, screw presses which use power screws to transmit
power and mechanical presses which utilizes kinematics linkage of element to transmit power. In
hydraulic press, the force generation transmission and application are achieved using fluid under
pressure. When the cassava mash is being loaded into the cassava presser, the cassava mash has
to be placed on the bottom plate of the presser, then the rectangular pressure plate when loaded
with bag(s) of cassava mash to exert a pressing force, thereby removing the water content of the
mash. The water content is also collected because of its economic importance and also to
eradicate pollution of the environment.
1.1
AIMS AND OBJECTIVES OF THE PROJECT
The aims and objectives of this project are:
I.
II.
III.
To design a hydraulic cassava presser
To improve on existing cassava presser
To produce a machine with large output per day
1
IV.
V.
VI.
VII.
To produce an hygienic product with less or no contamination
To produce a machine that has a longer life span
To provide a more positive response to change in input pressure
To also reduce the stress and human labor put into removal of water content from the
cassava mash.
1.2
RELEVANT OF THE PROJECT
The importance of the project to the field of mechanical engineering personnel and to the society
is to help the society and agricultural farmer who are into making of processed cassava “Garri”
to make it easier and faster.
After the design of the hydraulic cassava presser might have been perfected mass production can
be commenced.
1.3
ECONOMIC
IMPORTANCE
OF
CASSAVA
HYDRAULIC
PRESSING
MACHINE
Large percentage of people in Africa depend on cassava products, mainly “Garri “as food. The
ways of processing it is therefore paramount. One of the processing ways is the pressing of the
cassava mash to remove the water content with the use of cassava pressing machine. This will
aid the faster production of Garri.
Starch is another product which would be gotten from the collected water. Some part of this
country (Nigeria) use it for food and it has some other industrial uses.
The machine is therefore of high economic importance since it aids food production and
materials used in some industries.
The methodology used are from desk research, oral interview, network and creativity.
2
CHAPTER TWO
2.0 LITERATURE REVIEW
Cassava is known by various name in Nigeria, to mention a few, the plant is called "akpu" by
lgbos, "ege" by yorubas; "igan" by Ikas, rogo by Hausas: jakpu by Olukwumis. "Midaka" by
urohbos, "Twa" by "Anags/Ibibios. "Okponkoro" by jaws, and "bobzi" by "ishans". Nutritionally,
cassava contains potassium, iron, calcium, vitamin A, folic acid, sodium, vitamin C, vitamin B-6,
and protein. Cassava is applicable in many types of products such as food, confectionery,
sweeteners, glues, plywood, textiles, paper biodegradable products, monosodium glutamate and
drugs. Cassava chips are pellets are used in animal feed and alcohol production.
Some of the post-harvest equipment for cassava are:
I.
Peelers
VI.
Millers
II. Washers
VII.
Dryer
III. Graters
VIII.
Pelletizer
IV. Pressers
IX.
Sealers
V. Extruder
X.
Packaging materials e.g. containers, bags
Of all the post-harvest equipment for cassava, pressers are taken into consideration in this
project work.
After grating/grinding, the next processing step is to press the grated pulp to reduce its
moisture content.
3
In Africa, people used heavy stone placed on top of bags/basket filled with cassava mash.
More recently, screw pressed jack are used for greater efficiency and speed. The moisture
content of the mash is reduced from 60-70% to about 25%. The pressing time could be as short
as 15 minutes to the hydraulic press or as long 4-5 days when stone are relied upon.
2.1
USES OF CASSAVA
Cassava is used in the following areas
1. Ethanol: Cassava chips are an alternatives source of raw material for producing liquor as
well as medical and industrial alcohol.
2.
Livestock Feed: Cassava roots can be processed into chips are pellets which can be used
in compounding animal food for cattle, sheep, goats, pigs, poultry, and farmed fish. The
cassava leaves are also a good source of feed for livestock.
3. Food: Cassava is widely used in Nigeria as food. It is mostly consumed in the form of
garri, fufu, tapioca, starch, kpokpo, garri, and lafun. In the northern part of the country it
is eaten raw as snacks. Cassava flour is majorly used in bakery products and cassava
starch can be used as a general thickening agent.
4. Confectionery: Modified cassava starch or starch derivatives are used in confectionery
for different purposes such as thickening and glazing.
5. Monosodium Glutamate: Cassava starch is a common source of making monosodium
glutamate in Asia, it is used to enhance flavour in food e.g. Ajinomoto.
6. Pharmacy: Native and modified cassava starches are used as binders, fillers and
disintegrating agents for tablet production.
4
7. Biodegradable Products: Cassava starch can be used as a biodegradable polymer to
replace plastic in packaging materials.
8. Plywood: Glue made from cassava starch is a key material in plywood manufacturing.
The quality of plywood depends heavily on the glue that is used.
9. Paper: Modified cassava starch is used in the wet stage of paper making to flocculate the
pulp, improving run rate and reducing pulp loss.
10. Textile: Cassava starch is used in three stages of textile processing to size the yarn to
stiffen and protect it during weaving, to improve colour consistency during printing and
to make the fabric durable and shining at finishing.
2.2
SOME TYPES OF CASSAVA PRESSERS
A. TRADITIONAL TYPE
This is the use of heavy stone to remove the water content in the cassava mash, (Shown in fig
2.0 below).These heavy stoners are placed on top of bags or baskets which are filled with
cassava mash. This method is common in Africa. On some occasions, stones are not used, but
rather rope is used. This rope is put on the right and left side of the planks. After the placement
of the cassava mash, on the plank at the bottom, the plank for the top is placed on the mash and
the rope is drawn, Force is applied on the plank and the rope is tired tight enough so that all the
water content can be removed.
DISADVANTAGES OF TRADITIONAL METHOD
I. It takes longer time for the water content to be removed.
II. It requires more energy
5
III. The water content cannot be collected, making the environment to be polluted.
B. HYDRAULIC METHOD
Hydraulic press is the type of press that follows the Pascal law, which states that "the
pressure applied to a confined liquid is transmitted with undiminished force in every direction".
Force exerted on a particular area will generate greater force at the other end, capable of pressing
the mash. The hydraulic press, one of the simplest hydraulic machines is used like the
mechanical press; if this press is fixed to a frame and joined to a plate, it is capable of pressing
the cassava mash at small application of force, as shown in fig 2.1 below.
DISADVANTAGES OF HYDRAULIC METHOD
I. The ideal hydraulic press should have a constant viscosity at all temperature but this may
not exist, which can cause a setback.
II. Foaming in a hydraulic system can reduce the pump efficiency and cause loss of control.
III. Air in form of bubbles in the body of the fluid can cause problem.
C. ELECTRICAL METHOD
The electrical method utilizes the principle of power screw which provides the means for
obtaining large mechanical advantage capable of pressing out the water content from the cassava
mash with a minimum power input and maximum output performance. A prime mover is
provided with a switch to operate the screw to lift or lower the circular pressure plate. When
loaded, it transforms a rotary motion of the input number to a linear motion that perform the
required pressing.
The electric method is represented by the block diagram in fig 2.3 below
6
Power
+
Source
-
Electric
Motor
Speed
Reduction
Rotary
Motion
Transforms
to Linear
A Machine
member to
move in this
direction as
desired
Force Transmitted Used
For Pressing
DISADVANTAGES OF ELECTRIC METHOD
With all the appraisal of this method above it has the following disadvantages.
I. It is very expensive.
II. It requires the use of dry cell or electricity.
III. Wrong connection to power source can lead to accident.
2.4
HYDRAULIC PRESSER
The review of the history of hydraulic press will be done by carrying out a
comprehensive literature review of some its component e.g. hydraulic cylinder, end-cover plate,
piston, cylinder, flange bolt etc.
Hydraulic press is a machine using a hydraulic cylinder to generate a compressive force.
It uses the hydraulic equivalent of a machine, this was also known as a Barmah press after the
Investor (Joseph Bramah) of England. He invented and was Issued press, which depends on
7
Pascal's Principle the pressure throughout a closed system is content one part of the system is a
piston acting as a pump with a modest mechanical force acting on a small cross sectional area the
other part is piston with a larger area the generate a correspondingly large mechanical force.
According to (Joseph Bramah) in 1795, Braham's most Important invention was the
hydraulic press the hydraulic press depends on Pascal's principle that pressure throughout a
closed system is constant.
The press had two cylinder and pistons of different cross sectional areas. If a force was
exerted on the smaller piston, this would be transplanted into a large force on the large piston.
2.3
POWER SCREW CASSAVA PRESSER
The power screw cassava presser utilizes the principle of power screw which provides the
means for obtaining large mechanical advantage capable of pressing out water from the cassava
with a minimum power input and maximum output performance. They are used for greater
efficiency and speed. The moisture content of the mash is reduced from 70% to about 30% and
the pressing time could be as short as 1 hour compared with the hydraulic presser or as long as 45 days when stone are relied upon.
NEW INNOVATION ON POWER SCREW CASSAVA PRESSER
To reduce corrosion stainless steel plate is used to cover the U-channel (mild steel) that
will be pressing the cassava mash, and to make a container for the cassava mash. Also the water
is collected through pipe to disallow wet environment and the water can be used for starch in
food industry.
8
2.4
TERMINOLOGY OF SCREW THREADS
The terminology of screw threads is illustrated in the diagrams below. Thread form is
described in axial section. The square thread and the acme forms are commonly used in power
screws. Buttress thread can also be used.
A screw and not are to transmit power or motion. The axial movement of the nut is used
to drive a load.
The square thread is the most efficient for transferring torque to linear motion
The acme thread is easier to make, good when well lubricated and efficiency is slightly
lower than square thread.
The buttress thread is move efficient than acme closer to square than acme and used
when force is transmitted in only direction.
PITCH: This is the distance from a print on one thread to the corresponding print on the next
adjacent thread, measured parallel to the axis.
LEAD: This is the distance the screw would advance relative to the pitch.
HELIXANGLE (∝): is related to the lead and the pitch diameter Dp, by the equation.
………………. (2.1)
Tan ｽ = load
兀 Dp
NOMINAL DIAMETER: It is the diameter of the cylinder piece on which threads are cut.
9
CORE DIAMETER:
This is the diameter of a root of an external thread or diameter of the
crest of an internal thread.
EFFECTIVE DIAMETER: It is a diameter of an imaginary cylinder coronial with the thread,
which intersects the flanks of the thread in such a way as to make the width of the space between
thread equal. Hence effective diameter outside diameter minus the depth of thread.
This is DE=Dout – H
………………. (2.2)
DEPTH OF THREAD: It is the radial distance of the thread from crest to root of the thread
measured perpendicular to the longitudinal axis.
CREST: This is the top surface of the thread.
ROOT: It is the bottom surface created by two adjacent planks of the thread.
FLANK: This is the surface joining the crest and root.
SLOPE: It is the half of the pitch of the thread.
2.5 TURNING MOMENT AND LOAD
The turning moment and axial load are related to each other through the following
equation
Torque (Tdown) needed to lower a load is
Tdown =
…………………………… 2.3
10
Where
F= coefficient of friction
L = Lead
Dp = Pitch diameter
TUP =
………………………….. 2.4
11
CHAPTER THREE
3.0
MATERIALS AND METHODS
The power screw cassava pressing machine has a power screw which is housed by a nut.
The power screw is fixed with a turner at its top and its lower end is joined to a rectangular
pressure plate, through a bearing, so that when turning the screw the plate will not be turning
with it. This pressure plate is covered with a sheet of stainless steel to prevent corrosion. The
screw and pressure plate are carried by frame with a strong rectangular base so as to carry the
load effectively. It also has six stands. Seated on the base, is a stainless steel rectangular
container, so that it can collect the water when the mash is pressed. A hole is drilled on it to
allow the passage of water. A hose is fixed with this container to collect the water into a plastic
bowl.
3.1
SELECTION OF SCREW AND NUT DIMENSIONS.
Iso-metric threads, coarse, external, medium fit.
Tolerance class, 6g.
Bs 3643, part 2
For this design, a shaft of 45mm is considered, screw dimensions are:
Nominal (outside) diameter, Dn = 45mm
Effective (pitch) diameter = 22.674mm
Pitch, P=6mm (square thread)
12
Thread depth (H) for a square thread = 0.5p
H=0.5 x 6 = 3mm
………………….. 3.1
The core or root diameter, Dr = Dn -2H
3.2
DESIGN ANALYSIS/THEORY
Fluid power system is designed by objective (Sullivan 1975). The primary problem to be
solved in designing the system is man posing the desired performance of the system into system
hydraulic Schematic diagram of the hydraulic press volume flow rate and matching these
characteristic with an available input to the system to sustain operation.
The principal parameters of the design included the maximum load(5kN) the distance load
resistance has to move (piston stroke 150mm) the system pressure the cylinder area [piston
diameter 100mm) and the volume flow rate of the fluid. The critic component that required
design included rethydraulic cylinder, the frame, and the hydraulics circuit
3.3
FABRICATION OF THE MACHINE
CUTTING OPERATION
A 50mm x 50mm square pipe were cut into six pieces of length 300mm to be used for
legs. Two pieces of angle iron were cut to lengths 740mm each. Also sixteen pieces of the angle
iron were cut into lengths 270mm each. 100mm x 47mm U-channel was cut into two pieces of
lengths 760mm and two pieces of lengths 740mm. A length of 250mm was cut to be used for
housing of the nut.
13
Furthermore, a length of 705mm and six pieces of 200mm were cut, which was joined to
the stainless steel pressure plate.
Also, a plate of 703mm x 568mm was cut, then 19mm x 19mm and 19mm x 14mm were
cut out from the edges after scribing. A circular bar of diameter 45mm was cut, using power
hacksaw, to length 600mm. Also a circular bar of diameter 75mm was cut to length 530mm with
a power hacksaw, for the nut.
TURNING OPERATION
Part of the circular bar (shaft) for the powering, was turned on the lathe machine. A
length of 30mm was turned to 30mm diameter, then a length of 15mm was step turned to
diameter 20mm.
THREADING OPERATION
On lathe machine, the circular bar was held with the chuck and the tailstock firmly. A
cutting tool made of High Speed Steel (HSS) was used to make the thread of 6mm pitch on it.
The operation was also carried out on the nut, to get an internal thread of 6mm pitch.
DRILLING OPERATION
Drilling was done on a circular bar of diameter 75mm, length 100mm by using radial
drilling machine, using a drill bit of 45mm diameter, which was used as the nut before the
internal thread.
The center of the U-channel angle bar, for the top was drilled using radial drilling
machine with 45mm drill bit and the position for bolts was also drilled on the top U-channel
14
angle iron. Also the position for hose was drilled on the base container for easy passage of the
water content from cassava mash.
WELDING OPERATION
The angle irons of 270mm were welded to 740mm U-channel as the base. Eight pieces of
the angle irons were also welded on each sides of the U-channel. The two angle irons of 740mm
each were welded to hold the similar angle irons, which were initially welded to the U-channel.
The 740mm angle irons were welded to both sides to form the base.
The six 50mm by 50mm square pipe of length 300mm were welded to the base. Three
pieces were welded to both sides. The two 760mm U-channel were welded to the edges of the
middle U- channel at the base, to form a supporting frame. The 100mm nut was welded to the
drilled 250mm U-channel to house it. Six pieces of the U-channel of lengths 200mm was welded
with the 705mm U-channel, having three pieces on each side. This frame is then welded to the
square stainless steel plate of 575mm to form the pressure plate. Also, the bearing was welded to
the center of the pressure plate, which was joined to the power screw. The bottom plate was later
welded after folding operation to form the base containers.
OTHER OPERATIONS
The top supporting frame was bolted to the side supporting frame with bolts and nuts,
two on each sides. The U-channel, which housed the nut, was bolted to the top supporting frame,
using two pieces of bolts and nuts.
The power screw was screwed into the nut and the pressure plate was joined to it using a bolt.
15
Folding operation was done on the bottom plate by the use of folding machine.
16
CHAPTER FOUR
4.1
MATERIALS SELECTION
Based on the principles of material selection we considered the following:
1. The ability of the material to withstand service conditions.
2. The method(s) by which it is selected.
3. The overall cost of all the materials and processes.
PARTS
MATERIAL
TYPE/SHAPE
JUSTIFICATION
Solid/Circular
Can be machined for good
SELECTED
Power
Bright Mild Steel
dimensional
accuracy
and
relatively cheap.
Pressing Plate
Stainless Steel
Plate
Relatively cheap, wieldable,
strong,
and
corrosion
resistance
Bottom Container
Stainless Steel
Plate
Relatively cheap, wieldable,
strong,
and
resistance
Vertical Support
Mild Steel
U-Channel
17
Strong and rigid
corrosion
Base Support
Mild Steel
U-Channel
Rigid and relatively cheap
Bolts and nuts
Mild Steel
Hexagonal
Easily
available
and
relatively cheap
Delivery Pipe (Hose)
Rubber
Circular
Corrosion resistance
and detachable
Water Collector
Rubber Bowl
Bowl
Easily removable, corrosion
resistance and low density.
Here, a number of materials may be satisfactory in respect of fulfilling the service
requirements but based on the cost, rigidity and corrosion resistance, stainless steel, mild steel
and rubber were chosen for this particular project work.
4.2
ECONOMIC REQUIREMENTS
The economic requirement should take into account, the total cost of the component parts,
the cost of its manipulation, machining, joining and finishing. The overall costs of a member of
materials should be compared. The availability of a material will influence its cost and materials
available impose some limitations on the choice of material for fabrication of component parts of
the machine.
18
4.3
INVESTMENT OPPORTUNITY
This machine will be viable, because 70% of the Nigerian populations directly involved
in the production or the consumption of cassava product. Moreover, the machine can be used in
the pressing of palm oil. Palm oil is another agricultural product, which is indispensable in our
daily living. Therefore, investment opportunity is available to the following organization.
1 Industries wishing to establish a cassava and palm oil mill project.
2. Organizations directly processing cassava product e.g. Nation Root Corps Company (NRCC)
3. Organizations directly processing palm oil e.g. Nigeria Institution for Oil Palm Research
(NIFOPR).
19
CHAPTER FIVE
5.0
TESTING, RESULT AND DISCUSSION
5.1
TESTING
A fabricated machine is supposed to undergo test, to know if It can work as desired, to
know how efficient the machine is and to see if there could be necessary adjustment.
The fabricated power screw-pressing machine was tested by putting a wet bag of cassava
mash of mass 20kg into the stainless steel container. The power screw was rotated clock wisely,
through the handle, to lower the pressure plate, which in tum pressed the cassava mash.
5.2
RESULT/DISCUSSION
As the power screw was turned, the pressure plate was lowered to rest on the mash and
press it. The water content of the mash was drastically reduced and the new mass of the cassava
mash was 11kg.
The machine can press up to 200kg of cassava mash within one hour, conveniently. If
low speed is applied while turning the power screw and the screw is well lubricated, the
efficiency of the machine will be higher.
20
CHAPTER SIX
6.0
RECOMMENDATIONS AND CONCLUSION
6.1
RECOMMENDATIONS
With the results earlier got, the following recommendations are hereby given; the
development of local technology should be embarked upon to intentional standard. This should
be financed and supported by the government of this country so as to reduce over-dependency on
foreign products.
This machine is highly recommended for all cassava farmers in Nigeria, because it had
been improved upon; it can last longer and it can serve dual purposes i.e. removing water content
from mash and extracting starch.
The project student could know from the project work that there is need for the following;
There is need for vibration problem to be considered by future researchers, Maintenance aspect
should be an Important, which are of further consideration.
A coverage power requirement of about 26N recommendation for the hydraulic pump
that should be used. Also, a capacity of 80kN is also recommended for the hydraulic pump.
The final advice goes to the department and the school authorities that they should ensure
that they provide enabling environment and adequate machineries for the construction and
fabrication of this kind of project.
21
6.1
CONCLUSION
Power screw cassava pressing machine is highly helpful in the pressing of cassava mash.
The machine can reduce the water content from about 70% to 25%. It therefore minimizes the
consumable efforts compared to other existing pressing machines.
With the innovation on this fabrication Le, the use of stainless steel to cover the pressure
plate, to form a container on the base and the collection of water content into a bowl, the
machine will be It will serve for longer time and the environment will not be polluted.
Following the explanation, design analysis, material selection in this project work, more
of this machine can be produced.
Based on the steps taken and the outcome of the fabrication, which is the Stone hydraulic
press, it is very important that there is the need for proper planning and fabrication of any other
machine.
A 5ton hydraulic press was designed, manufactures and calibrated. The machine was
objectives and service ability, the machine was found to be satisfactory at a least load of 10 KN.
22
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Mechanics of materials. 2nd London.
AGARANAL D. D. et al (1987), Machine Drawing, New Delhi: Vikas Publishing House.
BLACK Paul H. et al (1982), Machine Design, Tokyo, Japan: Tosho Printing Co., Ltd.
Gupta, J.K (1997).A textbook of machine design. India Eurasia publishing.
HASLEHURST M. (1981), Manufacturing Technology, Great Britain: Hazell Wastson & Viney
Ltd.
Lange, K (1975); Handbook of metal forming, newyork Mc Graw- Hill, New York
Nebel, B. W., (1989) Modern manufacturing process engineering, Singapore, Mc Graw-Hill.
RAYMOND Higgins A (1989), Properties of Engineering Materials, Landon: ELBS.
SALAMI Sariyu O. (July 2003), Project report on Quality Characterizes of Dried Cassava flour,
Submitted to the Department of Foods Science and Technology, Ondo State Polytechnic,
Owo.
SAMTOBY Talkwell, (December, 2003), Project report on the Design and Construction of a
Cassava Press, Submitted to the Department of Mechanical Engineering Technology,
Ondo State Polytechnic, Owo, Ondo State.
Sharma, p.c. (2005). A textbook of production engineering. 10th ed., India, S. chand &co. Ltd.
Sullivan J.A (1975). Fluid power: theory and applications. USA Reston publishing.
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