Design analysis of an existing acha (digitariaexilis) dehulling machine

Abstract

An existing acha dehulling machine was improved upon by re-designing. The performance of the existing dehulling machine was first evaluated to determine the required modification. Im- provements were undertaken in the cylinder speed, cylinder-concave clearance, hopper slope and opening, cylinder type and fan speed. The physical properties, terminal velocities of acha and the acha chaff, velocity of air required for the cleaning were determined and used to re-design the machine. Major component parts were designed using relevant engineering design principles The modified acha dehuller had cylinder speed, cylinder-concave clearance, hopper slope, hop- per hole opening and fan speed of 2800 rpm, 10 mm, 57o, 10 mm and 2800 rpm respectively as against the existing dehuller values of 934 rpm, 20mm, 67o, 20 mm and 934 rpm respectively. Terminal velocities of acha and the acha chaff, velocity of air required for the cleaning deter- mined were 3.96 m/s, 1.9 m/s and 2.5 m/s respectively.