The performance of an Italian made combined machine was tested and evaluated for shelling and grading two different Egyptian corn crop varieties. Whereas, the optimum design, and operating parameters were determined in order to increase the mechanical shelling and grading efficiency and machine productivity. The crop was feed at a constant rate of 25 kg and at the grains recommended moisture content range of 12-14% (d.b). The shelling unit of the machine was deduced at four different drum speed levels (from 370 up to 820 rpm, those corresponding drum linear speeds from 4.84, up to 10.74 m/s). Also, shelling unit was tested under three concave clearance levels (32, 42 and 52mm). While, the grading unit deduced at different cylindrical screen speed levels (from 55, up to 95 rpm corresponding to linear cylinder speeds from 1.38, up to 2.39 m/s). The grading unit was also tested versus different cylindrical screen inclination angle up to 9 degrees. The tested machine performances were evaluated in terms of the grading and cleaning efficiency. In addition, costs per unit weight of production and energy unit requirements were estimated and compared with the traditional shelling and grading methods of corn crop. The obtained results revealed the following important points:
The optimum parameter levels for the mechanical shelling operation were drum speed of 670 rpm (8.77 m/s) and concave clearance of 42 mm. These parameters levels were recommended to match the performance of the grading unit. The promising parameters levels for operating the grading both tested crop varieties were 80rpm (2.00 m/s) for cylindrical screen speed and 3 degrees for inclination angle.As operating at the optimum parameter levels the highest values of grading efficiency (83.68 and 82.84 %), grading cleanliness (77.78 and 77.18 %), and machine capacity (0.51 and 0.47 ton/h) were achieved. for both tested corn varieties, SC10 and TC310 respectively. Also, the lowest values of specific energy consumption (25.94 and 29.29 kW.h/Mg) and cost (76.12 and 78.28 LE/ton) for both tested corn varieties, SC10 and TC310, respectively.