DEVELOPMENT OF CASSAVA GRATING MACHINE : A DUAL OPERATIONAL MODE

DEVELOPMENT OF CASSAVA GRATING MACHINE : A DUAL OPERATIONAL MODE

ABSTRACT

Development of Cassava Grating Machine : A dual Operational mode was investigated. The equipment has a realistic functional efficiency of 91.5% and 88.4% for manually and electrically powered operation with the discharge capacity 4.04 and 3.66 tons per day respectively. Simulation of its economic analysis shows between $2.6 and $3.0 could be saved while using automated cassava grater over manual system for 1-ton of cassava tuber. At 0.01 and 0.05 level of significance, it showed that the machine has a good economic potential over the convection method of grating. It saves time and labour requirements by a factor of 0.68. Design of a Cassava grating machine is dual-mode in operation; it is powered both manually and mechanically. This feature makes it useful in the rural areas where there is erratic or no power supply. Cassava is fed into machine through the hopper down to the granting drum, which rotates at a pre-set constant speed. Cassava is an important starchy root crop of the tropical world, the need to mechanize its growing and processing cannot be overemphasised.

 

 

 

 

 

 

CHAPTER 1

INTRODUCTION

 

Background of the Study

Cassava (Manihot esculenta Crantz) is a very important crop in Nigeria deriving from the extensive use of the various products and by-products as staples to most Nigerians. The consumption of cassava cuts across all parts of the country. It is a major source of carbohydrates in human diet, being processed into Garri, fatal and typical as a constituent for human food. Recently other areas of uses of cassava are being implored. It is also being used as starch [Adegeye, 1985]. The crop tolerance makes it more popular and now replacing yam in some part of Nigeria. The sweet varieties could be boiled for human consumption. Its adaptability to climatic and soil conditions even in marginal soils has endeared cassava to most people that have to do continuous cultivation on limited available land. Cassava is a shrubby, tropical, perennial plant that is not well known in the temperate zone. For most people, cassava is most commonly associated with tapioca. The plant grows tall, sometime reaching 15 feet, with leaves varying in shape and size. The edible parts are tuberous root and leaves. The tuber (root) is somewhat dark brown in color and grows up to 2 feet long. Cassava (manihot esculenta), has its origin as South America, presumably Eastern Brazil. It thrives better in poor soils them any other major food plants. Nigeria has been world-leading producer of cassava with an estimated annual production of 2.6 million tons from an estimated area of 1% million hectares of land [Agbetoye, 2005] and [CBN, 1994]. The major problem of cassava is that it is extremely perishable and the harvested tuber must be process to curb post-harvest losses [Davies, 1991]. According to food and Agriculture Organization [5] the estimated industrial cassava use was approximately, 16 percent of cassava root production and was utilized as an industrial raw material in 2001 in Nigeria. Around the world, cassava is a vital stable for about 500 million people. Cassava’s starching roots produce more food energy permit of land than any other staple crop. Nigeria is currently the largest cassava producer in the world with estimated annual production of about 40 million metric tons. About 90% of this is however, consumed as food. The country is yet to fully harness the socioeconomic potential of cassava that world translate to higher ranking of cassava next to petroleum as major contributor to the Goss Domestic Product (GDP). However, the need to mechanize cassava processing is enormous. The convectional cassava processing has a number of disadvantages and requires human energy and time and this has necessitated the design and development of mechanically-operated cassava grating machine. It was revealed that cassava peeling is still largely done manually; however, women and teenage girls are normally involved in the manual peeling of the tuber [Eagleston,1992]. The rate could be as high as 350 kg/day of 8 hour/person [Eagleston, 1992].

Usually, grating is done manually by using perforated plane sheets but such process is dangerous to human hands usually the user get wounds during grating. These problems led to the design and fabrication of machines that can grate the cassava of high quality in a short period of time and reduce human labor.

Ms. Elnor developed a cassava grater in 2006. The grating mechanism consists of a wooden grating drum. Based on the results of her study the presser is constricted that it creates much resistance in pushing and discharge hopper cannot prevent all the spills of cassava grates. The following problems were met and possible solutions were recommended.

 

 

Significance of the Study

Further enhancement in the machine will be done to improve its efficiency and capacity thus, the study is being propose so the following consideration will be taken care of the material to be use should be locally available, the develop grater must be affordable to small- scale cassava farmers, the machine can be fabricated in local machine shop, the machine should give reasonable production performance and it is easy to operate.

 

Objectives of the Study

The general objective of the study is on development of Cassava Grating Machine : A dual Operational mode, specifically it aimed to:

1. To design and fabricate a continuous disk- type cassava grater.
2. To evaluate the performance of the machine in terms of the capacity and efficiency the fineness modulus of grated cassava.
3. To develop grating machine with a dual Operational mode (manual and automatic mode of operation)

 

Scope and Limitations of the Study

The study is focused only on the design, fabrication and evaluation of the machine in terms of capacity, efficiency and fineness modulus of grated cassava.

 

Definition of Operational Terms

• Grater. A device with sharp-edged holes: a device with many sharp-edged holes against which something such as cheese can be rubbed to reduce it to shreds or fine particles.
• Weld. Welding, in engineering, any process in which two or more pieces of metal are joined together by the application of heat, pressure, or a combination of both. Most of the processes may be grouped into two main categories: pressure welding, in which the weld is achieved by pressure; and heat welding, in which the weld is achieved by heat. Heat welding is the most common welding process used today.
• Shaft. A rotating machine element which is used to transmit power from one place to another.
• Auger. Is a device that usually includes a rotating helical screw blade to act as a screw conveyor to push the commodity towards the other end.
• Receptacle. A space used to contain cassava tubes and grated cassava.
• Pitch. Is defined as the axial distance between adjacent threads on a helix or screw.  In most screws, called “single start” screws, which have a single helical thread along their length, the lead and pitch are equal.
• Angular speed. It is the time rate of turning of a body about an axis, or the rate at which a line on a revolving body is changing direction, and is expressed in angular units per unit of time.
• Fineness Modulus (FM). Is an empirical figure obtained by adding the total percentage of the sample of an aggregate retained on each of a specified series of sieves, and dividing the sum by 100. A smaller value indicates a finer aggregate. Finer aggregates range from a value of 2.00 to 4.00, and coarse aggregates smaller than 38.1 mm range from 6.50 to 8.00.

• Pulley system. A pulley system consists of two pulley wheels each on a shaft, connected by a belt. This transmits rotary motion and force from the input, or driver shaft, to the output, or driven shaft.
• Is a small hole in a thin metal sheet. There is usually more than one perforation in an organized manner, where all of the holes are called a perforation. The process of creating perforations is called perforating, which involves puncturing the workpiece with a tool.
• Disc cutter.This is a specialized, often hand-held, power tool used for cutting hard materials. This tool is uses an abrasive grinding wheel. Each grain of abrasive on the wheel’s surface cuts a small chip from the workpiece via shear deformation.
• V-belt. This belt is a circular cross section belt designed to run in a pulley with a 60 degree V-groove. The V-groove transmits torque through a wedging action, thus increasing friction.
• A pulley is a wheel on an axle or shaft that is designed to support movement and change of direction of a belt along its circumference. Pulleys are used in a variety of ways to lift loads, apply forces, and to transmit power.
• Frame. Is the structural component of equipment that provides the strength and rigidity overall.
• Electric motor. It is anelectrical machine that converts electrical energy into mechanical  Electric motors are used to produce linear or rotary force (torque).
• Shaft key. Akey fitting in a shaft to secure an operating part fastened in or to the shaft.
• Sieve or sifter. Is a device for separating wanted elements from unwanted material or for characterizing the particle size distribution of a sample, typically using a woven screen such as a mesh or net.
• Pillow block. It is a pedestal used to provide support for a rotating shaft with the help of compatiblebearings & various accessories. Housing material for a pillow block is typically made of cast iron or cast steel.
• Mechanical efficiency.This measures the effectiveness of a machine in transforming the energy and power that is input to the device into an output force and movement.

 

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