Design and fabrication of a motorised maize sheller.

Abstract

Maize (Zea mays L) is one of the world's important cereal crops and a major staple food in East Africa. In addition to its being an important animal feed, it's also a source of income. Shelling is the process of removing seed or grain from their respective cobs for both human and industrial use. The bulk of the crop is shelled using the rudimentary traditional methods, which have low productivity and result into maize grain of low market value. Earlier studies conducted by National Agricultural Research Organization (NARO) in 1989 identified lack of appropriate maize sheller to meet the market demands of commercial farmers as one of the major constraints that mitigate the increased trends of maize production in Uganda. Responded by developing a motorized maize sheller, which had a mean output of 300kg/hr, shelling efficiency of 53% and mean damaged grain of 15%. Designing and constructing of the various components of the maize sheller involved determining the appropriate angle of repose of maize grits, a suitable gate size for the hopper, determining the pneumatic pressure developed by the blower to remove chuff from the grains and analyzing forces acting on the components to prevent failure of the sheller during operation. Force analysis led to selection of proper materials to withstand the forces to avoid failure. Engineering drawings of the various components of the maize sheller were designed before the machine was constructed and assembled. The performance of the sheller after construction was evaluated taking into consideration of capacity, efficiency and power requirement. The obtained results reveal that it is recommended to operate the sheller at a rotational speed of about 525 rpm, grain moisture content of 13%, sheller clearance of 3mm. Therefore, it is recommended that, this maize sheller should be manufactured and popularized for adoption in Uganda and will help reduce power consumption as well as increase profits to the maize producers.