ABSTRACT
A motorized cassava tuber chipping machine was designed, constructed and evaluated. The objectives of the research are to investigate the effect of moisture content and speed on the chipping sizes, efficiency, throughput and machine capacities. Results obtained showed that the cassava initial moisture content significantly affected the chipping size, machine capacity and throughput capacity but not chipping efficiency within the tested moisture content range of 53 to 68 % wet basis. The machine speed affected the chipping size, chipping efficiency, machine and throughput capacity. The average chipping size for the cassava chips at the four ranges of moisture content, speeds and constant feed rate of 89±26.6 kg/hr ranged from 0.56 to 0.96 cm. The average chipping efficiency ranged from 60 to 90 % while the throughput capacities of the machine ranged from 49 to118 kg/hr. Also for the machine capacity the average values obtained were 44 to 100 kg/hr.
TABLE OF CONTENTS
Title Page i
Declaration Page ii
Certification Page iii
Dedication iv
Acknowledgement v
Table of Content vi
List of Tables viii
List of Figures x
List of Plates ` xi
Abstract xii
CHAPTER 1: INTRODUCTION 1
1.1 Background to the Study 1
1.2 Statement of the Problem 2
1.3 Aim and Objectives of the Study 2
1.4 Justification of the Study 3
1.5 Scope of the Study 3
CHAPTER 2: LITERATURE REVIEW 4
2.1 Review of Existing cassava chipping machines 4
2.2 Industrial Products from Cassava 5
2.3 Secondary Products from Cassava 6
CHAPTER 3: MATERIALS AND METHODS 8
3.1 Design features of the Cassava Chipping Machine 8
3.2 Design Considerations of the Machine 9
3.2.1 Pulley Design 9
3.2.2 Angle of Wrap (∝) for the Pulleys 10
3.2.3 Belt Design 10
3.2.4 Belt Center Distance 11
3.2.5 Belt Contact Angle (β) 11
3.2.6 Belt Speed, Tension and Power Computations 12
3.2.7 Shaft Design 13
3.2.8 Determination of Bending Moment at each Point of Loading. 14
3.2.8.1 Force exerted on shaft (vertical force). 15
3.2.8.2 Reactions at the bearings. 16
3.2.8.3 Shear force computation (Q) 18
3.2.9 Bearing Selection. 19
3.3 Materials, Cost (Bill of Engineering Measurement and Evaluation) and fabrication procedures 20
3.4 Experimental procedure 23
3.5 Performance Evaluation 24
3.6 Data analysis 24
CHAPTER 4: RESULT AND DISCUSSION 25
4.1 Description and Principle of Operation of a Cassava Chipping Machine. 25
4.2 Effect of Speed on Chipping Size of Cassava Chips. 27
4.3 Effect of Moisture Content on Chipping Size of a Cassava Chips. 29
4.4 Effect of Speed on Chipping Efficiency 29
4.5 Effect of Moisture Content on Chipping Efficiency. 31
4.6 Effect of Speed on Throughput Capacity and machine capacity. 32
4.7 Effect of Moisture Content on throughput and machine capacity. 34
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS 37
5.1 Conclusion 37
5.2 Recommendations 37
REFERENCES 38
APPENDICES 41
LIST OF TABLES
3.1: Material Selection. 20
3.2: Materials and Costs 20
3.3: Construction Procedures. 22
4.1: ANOVA table for interaction of chipping size at different moisture content and chipping speed. 28
4.2: ANOVA table for interaction of chipping size at different moisture content and chipping speed 31
4.3: ANOVA table for interaction of throughput capacity at different moisture content and chipping speed 34
4.4: ANOVA table for interaction of machine capacity at different moisture content and chipping speed 34
8: Thickness of 30 samples of Cassava Chips (cm) at 68% moisture content on a wet basis using four different speed variations. 55
9: Thickness of a 30 samples of Cassava Chips (cm) at 63% moisture content on a wet basis using four different speed variations. 56
10: Thickness of a 30 samples of Cassava Chips (cm) at 58% moisture content on a wet basis using four different speed variations. 58
11: Thickness of a 30 samples of Cassava Chips (cm) at 53% moisture content on a wet basis using four different speed variations. 60
12: Results of Machine Capacity, Throughput Capacity, Feeding Rate and Chipping Efficiency obtained from moisture content of Cassava tubers at 68% on a wet basis. 61
13: Results of Machine Capacity, Throughput Capacity, Feeding Rate and Chipping Efficiency obtained from moisture content of Cassava tubers at 63% on a wet basis. 62
14: Results of Machine Capacity, Throughput Capacity, Feeding Rate and Chipping Efficiency obtained from moisture content of Cassava tubers at 58% on a wet basis. 62
15: Results of Machine Capacity, Throughput Capacity, Feeding Rate and Chipping Efficiency obtained from moisture content of Cassava tubers at 53% on a wet basis. 63
LIST OF FIGURES
3.1: Belt Center Distance (C) Diagram. 11
3.2: Belt Tension Diagram. 12
3.3: Shaft, Bearing, cutting blade and pulley assembly. 15
3.4: Free body diagram of vertical forces acting on the shaft. 16
3.5: Moment about the bearing points. 16
3.6: Shear force and bending moment diagram of the cassava chipping machine 19
4.1: Isometric View of the Cassava Chipping Machine 26
4.1.1: Orthographic view of a cassava chipping machine 27
4.2: Effect of machine speed on the chipped sizes of cassava chips 28
4.3: Effect of moisture content on the chipped sizes of cassava chips 29
4.4: Effect of speed on the chipping efficiency of the cassava chipper at different moisture content 30
4.5: Effect of moisture content on the chipping efficiency of the cassava chipper at different speed 32
4.6: Effect of speed on the throughput capacity of the cassava chipper at different moisture content 33
4.7: Effect of speed on the machine capacity of the cassava chipper at different moisture content 33
4.8: Effect of moisture content on the throughput and machine capacity of the cassava chipper at different speed 35
4.9: Effect of moisture content on the throughput and machine capacity of the cassava chipper at different speed 36
LIST OF PLATES
1: Component Parts of a Cassava Chipping Machine. 42
2: Assembling of Some Parts of a Cassava Chipping Machine. 43
3: Base (Frame) of a Cassava Chipping Machine. 44
5: Assembly of a Cassava Chipping Machine. 45
6: Feeding Unit cum Chipping Chamber. 46
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND TO THE STUDY
Cassava, (Manihot esculanta crantz,) is a perennial plant which belongs to the family of Euphorbiaceae. Cassava has been emphasized as an important source of food energy in Nigerian diets and plays an important role in easing food crises due to its year round availability, suitability to farming method of Nigerian farmers (Ajibola, 2000). It was reported that Cassava was brought into Nigeria by slaves returning from South America (Ikugbayigbe, 1992). It grows well in tropical soil and Nigeria has become one of the largest producers of cassava in the world (FAO, 2006). It produces good yield even in poor soil and the ability to stay in the soil for long duration post maturity makes it a veritable part of food security crop for low-income countries. Cassava has become a major cash crop, food, and raw materials for the making of starch, alcohol, pharmaceuticals and confectioneries (Francisco, 2004). Cassava forms a base for a wide variety of fermented foods in most emergent country and serves as unprocessed substance in the manufacture of processed foods, animal feed and industrial products (Aloy et al 2006). It can be consumed as gari, chips, flour, fermented pastes and starch etc. (Annebunwa et al., 1998). Therefore it has formed a major part of the staple food and major source of carbohydrates in most tropical countries competing with other tubers like yam (Balogopalan 2002).
Cassava deteriorates fast and must be processed to other form if it must be stored (Silayo et al., 2007. Thus, there is a need for rapid processing of the tubers into a more shelf stable form (IITA, 1990). Nigeria currently is the largest producer of cassava in the world (Ndukwu e al., 2018). Processing the tubers into dried chips reduced the moisture content to a very low level and reduced postharvest losses (Ugwu 1996). In a country (Nigeria) separately from undeviating processing at local level and utilization, animal feed, the verdict of the Federal Government for addition of cassava flour of about 10% in bakery and cassava chips send abroad mission, improved the stipulate for cassava manufacture. In continent like Asia, more than 40% of the cassava is for undeviating human utilization, with greatly of the remnants exported as chips. In India, scorched roots are transformed into small chips and flour. In a country like Indonesia, 57% production of cassava is for human utilization while 43% are consumed boiled or processed into dried chips before consumption (IITA 2005). Cassava processing into chips aids in rapid drying of the crops, lowers its bulk density and eases its packaging, transportation and export. Several cassava chippers has been developed in literature and has been extensively reviewed by Ndukwu et al (2018). However, there is scarcity of information of the outcome of operational parameters on the machine capacities and thickness of cassava chips produced by this machine.
1.2 STATEMENT OF THE PROBLEM
The short shelf-life and bulkiness of cassava roots pose a great problem in transporting it from the farm to the market or factory sites due to its extremely perishable nature. Processing of cassava into chips by manual methods like application of knife involves high labour input and also results in low product quality.
1.3 AIM AND OBJECTIVES OF THE STUDY
The aim of this work is to develop a cassava chipping machine. The specific objectives include:
- Design and select components of cassava chipping machine.
- To fabricate the designed cassava chipping machine.
- To determine the effect of moisture and chipping speed on machine efficiency, throughput capacity, machine capacity and chip sizes.
1.4 JUSTIFICATION OF THE STUDY
To overcome the difficulty in the marketing and utilization of cassava and to avoid heavy post-harvest losses, the roots need to be processed into some form of dried product with longer shelf life. The easiest and most common means of processing cassava is the alteration of the roots into dry chips. Processing of Cassava into chips by manual methods which entail the use of knife is labour-intensive with lots of human drudgery but the appliance of enhanced processing knowledge (skill) has drastically abridged processing time and labour and encouraged advance production.
1.5 SCOPE OF THE STUDY
This project work was limited to the design and construction of a cassava chipping machine. The essence of chipping was to increase the surface area of cassava for rapid drying which will enhance its processing into cassava flour.
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