Mechanical Engineering Project Topics

Design and Construction of a Cassava Grating Machine

Design and Construction of a Cassava Grating Machine

Design and Construction of a Cassava Grating Machine

Chapter One

Objectives Of The Study

The following research objectives needs to be accomplished:

  1. To design and fabricate model cassava grater.
  2. To modify the design of the existing cassava grater (dimensions) to the home use small scale size.
  3. To change the crude wooden hopper and chutes used in cassava grating machines to lasting stainless steel.
  4. To save time and cost of processing cassava products by the average family.
  5. To promote health consumption of cassava products



Traditional cassava processing does not require sophisticated equipment. Processing cassava into garri requires equipment such as grater, presser, and fryer.  The traditional cassava grater is made of a flattened kerosene tin or iron sheet made of a flattened kerosene tin or iron sheet perforated with nails and fastened onto a wooden board with handles.  Grating is done by rubbing the peeled roots against the rough perforated surface of the iron sheet which tears off the peeled cassava root fresh into mesh.  In recent years, various attempts have been made to improve grater.

Onyesola (1981) reported that the traditional method of grating involves placing of the local grater, which is made of perforated metal sheet on the table where it is convenient for effective use by brushing the cassava on the perforated metal sheet.  The cassava then turns into pulp and drop into the container that serves as a collector.

Adejumo (1995) in his design used a wooden grater in which the cassava roots are forced into a hopper and are rubbed against the greater which is being powered electrically.  Nevertheless, enhanced quality of cassava can be grated using this method.  However, the durability of grater is low because of its wooden nature.

In this design the cassava grater consist basically of three(3) units.  The hopper unit, the grating unit and the delivery unit.  All these components are mounted on an angle iron frame.  The machine assembly is powered mechanically by the use of 175 diesel engine.  It can be use in rural settlements where electricity supply might not be available due to its mobility.

Cassava grater is a compact, convince and useful machine for scratching or grating cassava. The main components of cassava grater are molded drum, feeler bin and exit channel. Molded drum is made up of metal usually aluminum where as feeder bin, exit channel is made up of heavy duty galvanized sheet metal.

The graters are available in different sizes and capacities.   Cassava grater comes in two version – mobile and stationary mobile grater has a motor wheel which facilitate movement.

On the basis of their sizes and functions cassava grater are of different types.





Shaft Design

A shaft is a rotating machine element which is used to transmit power from one place to another.  The power is transmitted by some tangential force and the resultant torque set up within the shafts that permits the power to be transferred to various machine or its elements linked up to the shaft.  In order to transfer the power from the shaft, the various members such as pulleys bearing drum etcetera are mounted on it.  These members along with the force exerted upon them cause the shaft to bending.

Therefore, we may say that shaft in this case is exposed to bending moment and torsional forces since it is utilized for torque transmission and bending moment.



Machineries and Machining Process Used In Fabrication Processes are as Follows:

  1. Drilling Machine: This can be hard drilling or pillar drilling machines. This machinery was used for most drilling jobs. The work is stationary while the spindle carrying the drill chuks and bit moves, the work, must be held with a vice during drilling.



Series of test were conduced using the machine. Cassava tubers were obtained from a farm peeled manually, thoroughly washed and weighed using weighing balance scale.  The machine was operated for some minute to allow speed to stabilize, peeled cassava was introduced into the machine through the hopper and a piece of wood was used to press the cassava against the drum to avoid /prevent scattering of the cassava caused by machine vibration.

The time taken to grate a quality of the cassava was obtained and recorded.


This is quotient of the cassava grated per time taken.

Efficiency of machine is given by

∫g   =     weight of cassava grated  (kg)

Time taken (Hr)

For existing machinery, 5kg of cassava was grated under 120seconds.


∫g   =     5 x 3600 kg


=     150kg/hr


The home use/ small scale cassava grating machine was designed, constructed and tested it was found to be effective and efficient and could grate abut 150kg/hr.

This machine can be used at home-scale for domestic applications. Based on the construction materials selection and quality of fabrication work, the machine is durable and expected to last for years.


Having considered the design process and analysis I recommend that it is paramount vital to carryout adequate servicing of the machine.  Daily washing of the machine after use specially the lanced metal sheet (grater) to remove or dislodge the reminant of cassava and other dirt will enhance and prolong the life of the machine.

It is also recommendable that further research be carried out on how to increase the volume of the hopper by increasing the size of the whole design in way of making it comfortable for more commercial use.

Furthermore, in this design, arc welding is used as a means of metal joining. I suggest in future that other means of metal joining should be considered, especially when joining the stainless hopper for better and smooth surface finish.

Results and Discussion

Cassava Grater Drawings

Engineers use CAD to create two-and-three dimensional drawings, such as those for automobile and airplane parts, floor, plants, maps and machine assembly.  While it may be faster for an engineer to create an initial drawing by hand, it is much more efficient to change and adjust drawings by computer.

In the design stage, drafting and computer graphics techniques are combined to produce models of different graters.  We manipulate these model on video displays screens unit they incorporate the best balance of features, including ease of production and cost.  Using a computer to perform the six-step “art-to-part” process:

The first two steps in this process are the use of sketching software to capture the initial design ideas and to produce accurate engineering drawings.

  • The third step is rendering an accurate image of what the part will look like.
  • Next, engineers use analysis software to ensure that the part is strong enough.
  • Step five is the production of a prototype, or model.
  • In the final step the CAM software controls the machine that produces the parts.

During the design of the machine, the drafting software we used was AUTOCAD 2007 version.  This was used to draw the orthogonal views, isometric views and exploded drawings of the model cassava grater before the commencement of the fabrication process.


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