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Abstract
A reciprocating motion cassava shredder was designed, fabricated and evaluated. The machine consists essentially of a hopper where peeled cassava roots are put. Directly beneath the hopper is the shredding plate coupled to a horizontal shaft which when in operation undergoes reciprocating motion. The shredding plate is enclosed within the collector assembly. The horizontal shaft derives its motion through a slider and crank mechanism coupled to an electric motor via a belt drive with a pulley for primary speed reduction and regulation. A rugged framework is provided for mounting the machine and electric motor. The capacity of the machine is 320kg/hr. Experimental evaluation results showed that the size of the shredding aperture of the machine significantly affected the shredding efficiency of the machine. The shredding efficiency of the machine decreased with increasing shredding aperture, but increased with shredding speed. Maximum shredding efficiency of 92% was obtained when the shred aperture was 3mm and the shredding speed was 975rpm. The throughput capacity of the machine increased with speed of shredding with a maximum value of 319.89kg/hr at 975rpm and a minimum value of 301.54kg/hr
TABLE OF CONTENT
Title page – – – – – – – – – – i
Declaration – – – – – – – – – – ii
Certification – – – – – – – – – iii
Dedication – – – – – – – – – – iv
Acknowledgement – – – – – – – – v
Abstract – – – – – – – – – – vi
Chapter One
1.1 Introduction – – – – – – – – – 1
1.2 Statement of problems – – – – – – – 3
1.3 Aim – – – – – – – – – – 4
1.4 Objectives of the project – – – – – – – 4
1.5 Scope of the project – – – – – – – 4
1.6 Importance of the project – – – – – – 4
Chapter Two
2.1 History – – – – – – – – – 6
2.2 Cassava processing – – – – – – – 6
2.3 Summary of literature review – – – – – – 19
Chapter Three
3.1 Design consideration and design analysis – – – – 20
3.1.2 Mechanical factors – – – – – – – 20
3.1.3 Operational factors – – – – – – – – 21
3.1.4 Economic factors – – – – – – – – 21
3.2 Description of the cassava shredding machine – – – 21
3.2.1 Design analysis – – – – – – – – 22
3.2.2 To determine the size of the hopper – – – – – 22
3.2.3 Volume of a rectangular based pyramid – – – – 23
3.4 Belt length – – – – – – – – – 23
3.4.1 Shaft design – – – – – – – – – 24
3.4.2 Design of the frames – – – – – – – 26
3.4.3 Bolts selection for the frames – – – – – – 27
3.4.4 Electric motor power – – – – – – – 28
3.4.5 Pulleys – – – – – – – – – 29
3.5 Materials selection – – – – — – – 31
3.6 Fabrication techniques – – – – – – – 34
Chapter Four
4.1 Testing/results and discussion – – – – – – 41
4.2 Shredding efficiency – – – – – – – 42
Chapter Five`
5.1 Conclusion – – – – – – – – – 46
5.2 Recommendation – – – – – – – – 47
References – – – – – – – – – 48
Appendixes – – – – – – – – – 50
CHAPTER ONE
1.1 INTRODUCTION
Cassava is one of the most important crops in Africa. It belongs to Plantae kingdom, Euphorbiaceae family and genus Manihot (FAO 1995). It is the third largest source of food carbohydrates in the tropics after rice and maize. (Olsen and Schael 1999). The leaves and tender shoots of cassava are also consumed as vegetables that are rich in vitamins and proteins (Krochmal and Hahn, 1991).Over two thirds of the total production of the cassava crop is consumed in various forms by humans and livestock. Its usage as a source of ethanol for fuel, energy in animal feed, and starch for industry is increasing. The crop is amenable to agronomic as well as genetic improvement, has a high yield potential under good conditions and performs better than other crops under sub optimal conditions. It is grown widely in several countries in sub-Saharan Africa and Madagascar. It was introduced into Africa in the latter half of the 16th century from South America. Nigeria is rated as the world largest producer of cassava, (IITA, 1990). Cassava has become one of the prominent crops that are required to be provided for both local consumption and export promotion. In 2004, a policy was initiated by the federal government of Nigeria to produce bread with cassava and wheat flour in the ratio of 1:9 in Nigerian bakery industry. Apart from human consumption, cassava is also used for animal feed and alcohol production (Cork J.H 1987). Cassava is classified as sweet or bitter. Like other root and tubers cassava contains antinutritional factors and toxins. It must be properly prepared before consumption. Improper preparation of cassava can leave enough residual cyanide to cause acute cyanide intoxication, paralysis and death (FAO 1990). Storage of fresh cassava roots is often unsatisfactory because of high spoilage rate and deterioration of quality of the stored whole roots with time (Jeon and Halos, 1991). Cutting of cassava tubers into small chips or shreds is an efficient way to aid drying. Drying provides a solution to maintain the quality of roots and improves the storability of the products. Chipping has been found to hasten the drying rate and improve the quality of the product (Rupert, 1979).
Shredding is a size reduction process (Brennan and Butters, 1981).Therefore shredding has potentials to improve cassava products quality, even though the process is not widely used in cassava processing. Reducing the size of the roots to be processed into a food product which requires fermentation and drying has been recognized as an effective method of reducing processing time and improving the product quality (Jeon and Halos, 1991). Cassava shreds known within the Eastern parts of Nigeria as Ighu, Nsisa, Ijapu or Abacha are a local delicacy. It is made from peeled and shredded cassava roots, after steaming and fermentation for about 24 hours. The product is then washed and eaten as a snack or made into a main meal or dried for storage. Cassava shredding is still done manually. Peeled and steamed cassava is moved vigorously by hand over metallic shredding plates to effect the shredding action, or by the use of kitchen knives. The mechanization of cassava shredding introduces changes in the quality characteristics of the shreds produced. The nature of these changes will depend on the interaction of the machine, process and raw material variables. Hence the objective of this work is to design and fabricates a reciprocating motion cassava shredder that will be suitable for small scale cassava shreds (Abacha) production and evaluate the machine for performance during testing.
1.2 PROBLEMS STATEMENT
From the survey conducted, it was discovered that most of the cassava shredder in the research area are usually corroding (reducing service life) due to the acidic nature of the cassava fluid and materials used for the fabrication. To ensure all cassava products is free from any taste, odour, or infected by iron content of parts (food poisoning) which may affect the quality of their contents (FAO/GIEWS, 2001) hence need to modify the design and use appropriate. Material manual chipping or shying of cassava tubing into chips involves much drudgery and is time consuming.
1.3 AIM
The aim of this project is to design and fabricate a cassava shredding machine that utilizes an effective method of shredding Cassava in order to eliminate the under listed problems caused by the manual method.
1.4OBJECTIVES OF THIS PROJECT
The objectives pursued in this project are as follows
- Time consuming, To reduce time consumed using manual on chipping.
- Low efficiency, To improve on the capacity of existing chipping machine
- Quantity of product. To improve quality cassava chips, by eliminating product contamination
- Economic effective. To develop a cost effective and affordable chipping machine for local productions.
1.5 SCOPE OF THE PROJECT
The scope of this project encompasses the design and fabrication of cassava shredding machine using mechanical method.
1.6 IMPORTANCE OF THE PROJECT
The significance of the cassava shredding machine involves the following;
o It is easy to maintain,
o It is economical,
o It increases the rate of productivity,
o It is durable,
o It’s affordable.
It makes the production process of our locally made food called ‘Ijapu’ easier and faster for the producer.