The present research was carried out to develop and estimate some operating parameters and affecting the performance of a rice milling machine to improve product quality. The rice milling machine was developed by adding two units: cleaning unit to remove chaff and other foreign materials from rice grains before the milling operation and feed unit to adjust rice feed rate. The performance of the developed milling machine was studied under the following parameters: feed rate, drum speed, and grain moisture content in terms of overall machine efficiency, total grains losses, machine productivity, required power, specific energy and criterion cost. The experimental results reveal that the highest values of machine productivity and overall machine efficiency were 1.08, 1.17 and 1.35 Mg/h; and 95.00, 95.38 and 95.66 % for Sakha-101, Giza-171 and Sakha-105 varieties, respectively, while the lowest values of required power and specific energy were 13.0, 13.4 and 13.8 kW; and 17.40, 15.68 and 13.85 kW.h/Mg, respectively, for the same rice varieties, furthermore the lowest values of both operational and criterion costs were 8.53, 7.87 and 6.82 L.E./Mg; and 35.96, 31.96 and 29.38 L.E./Mg, respectively, for the same rice varieties. Results of mechanical analysis of the manufactured cleaning and feeding units reveal to the following:
Sieve speed, sieve tilt angle and cleaning air velocity of about 400 rpm, 4.0 deg and 6.5 m/s.
Mechanical feeding rate of 1.4 Mg/h for Sakha-101 variety and 1.6 Mg/h for both Giza-171 and Sakha-105 varieties.
From the experimented results, it could be concluded that the optimum operating parameters for the developed milling machine were found at:
Drum speed of about 800 rpm for Sakha-101 and 850 rpm for both Giza-171 and Sakha-105 varieties.
Grain moisture content of about 14 % for Sakha-101 and 15 % for both Giza-171 and Sakha-105 varieties.