DESIGN, CONSTRUCTION AND TESTING OF CASSAVA PELLETIZING MACHINE

Abstract

This project is on the design, construction and testing of a cassava pelletizing machine. The machine processes cassava mash by extrusion into cylindrical form of about 2-3cm length and 9mm diameter called pellets. The machine is made of these major components: hopper, barrel, auger conveyor and a circular die plate. The hopper is made of a stainless steel 1mm thick cut from a flat metal sheet. The sides if the hopper is joined by electric arc welding while the barrel is a cylindrical hollow shaft. This barrel is welded to the already fabricated hopper at its base, with the base of the hopper coinciding with an opening in one end of the barrel and the other end welded to an already perforated die plate. The auger conveyor is an intricate part of the machine made of a shaft wound round with a 20mm rod joined by arc welding with honcon electrode. A helical auger is mounted on a shaft which is supported on bearings so that the shaft rotates freely in the stationary cylindrical barrel. Cassava mash is introduced into auger through the inlet gate of the barrel. The auger conveys the mash to the die and builds up pressure for its extrusion. Pressure resulting from rotating auger forces the mash through the perforations in the die, compressing and forming it into pellets. Experiments were conducted to compare the moisture content of the pellets and that of the unpelletized cassava mash using the oven method and also to determine the production rate and efficiency of the machine. Experimental results revealed that the pellets had a moisture content of 16.49% (d.b) and cassava mash 75.20% (d.b). The results also indicated that the pellets have more durability than the cassava mash since high moisture content have been found to decay mash faster hence the need for pelletizing. Furthermore, the production rate and efficiency of the machine were found to be 63.86g/min and 81.27% respectively. Though the performance of the machine is satisfactory, I recommend that a force feed mechanism be introduced to avoid caking of the mash especially while operating on large quantity and also the noice level minimized.