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An existing mechanical rice de-stoner was modified for the purpose of improving its efficiency. Some challenges were discovered with the performance of the existing machine that did not make it to perform effectively. The spring, cushion rubber, coil, capacitor, cable and plug were incorporated to modify the existing mechanical rice de-stoner. After modification of the machine, performance evaluation was carried out. A total of 6 kg of threshed rice sample was mixed with stones sized 2.36mm and was divided into three parts of 1.5kg, 2.0kg and 2.5kg and labelled A, B and C respectively. Each part was fed at different times into the rice de-stoner and de-stoned. Also, 200g of the threshed rice were taken for hand-picked which served as the control for separating and other foreign materials from the rice. This was used to compare the result of the efficiency of the machine. The efficiency of the handpicked method was determined to be 80% while that of the modified de-stoner was determined to be 66.7%, 60% and 64% respectively. Thus the performance evaluation of the mechanical rice de-stoner was rated above average but not as effective as the hand-picked method. Also, the machine`s throughput capacity was 13.60 kg/hr, 15.38 kg/hr and 15.38 kg/hr for the feed rates of 1.5kg, 2.0kg and 2.5kg respectively.. Thus, the modified mechanical rice de-stoner machine was to be used as a template for other new rice de-stoner to be constructed.
Koyenikan et al. (Sat,) studied this question.