PERFORMANCE EVALUATION AND MODIFICATION OF THE IPHT FINGER MILLET DE-STONING MACHINE

A study was carried out to modify the finger millet (Kurakkan) De-Stoner, developed by the Institute of Post-Harvest Technology in Sri Lanka (IPHT) for separation of the grains from foreign materials and stones, based on the principle of difference in velocities of motion between the finger millets and stones on a rough inclined plane. The modification was carried out on re-designing of the machine supports and adjustment devices, reconstruction of collecting hoppers and feeding hopper, construction of a wiping brush and two supporting rollers for the inclined plane. Performance of the modified machine was evaluated by determining its capacity, separation efficiency, power transmission efficiency, power consumption, cost of separation and total cost of machine. This modified machine has a capacity of 12kg/hr. at the optimum speed of 30rpm and 10-degree angle of the separating surface (conveyor belt) and cost of separation is Rs.2.10/kg. The de-stoning efficiency of machine during the first, second, and third passes is 86.34%, 89.34%, and 94.47% respectively. The power consumption of the machine is 0.69kw and power transmission efficiency of machine is 96%.