OPTIMIZATION OF DESIGN PARAMETERS FOR PORTABLE COMMON BEANS (Phaseolus vulgaris L) THRESHER USING TAGUCHI METHOD

Abstract

Portable threshers are widely used in developing countries for threshing and cleaning cereal grain. This paper focuses on the optimization of design parameters using the Taguchi method of common beans (Phaseolus vulgaris L) thresher. The optimization criteria were to minimize grain damage and power required for threshing while maximizing the threshing efficiency and throughput capacity of the machine. The experiments were conducted on modelled and simulated common beans thresher. The main input variables for the unthreshed common beans and machine were the peripheral velocity of the pegs, bulk density of the crop, feed rate, concave width, moisture content, and mass of the threshing cylinder. An experimental design with an orthogonal array of L₂₅ (5⁶) was used. Optimum mechanical grain damage was obtained at a factor combination of 2 m/s peripheral velocities of the pegs, 0.01 kg/s feed rate, 1 m concave width, 22.5 % moisture content wet basis, and 10 kg mass of the threshing cylinder. Optimum threshing efficiency of 99% corresponds to pegs speed of 10 m/s, unthreshed common beans bulk density of 44 kg/m³, feed rate of 0.01 kg/s, 1 m concave width, crop moisture content of 15 %, and 8 kg mass of the threshing cylinder. In the case of throughput capacity, the optimum output of 95 kg/hr was obtained at pegs speed of 10 m/s, crop bulk density of 44 kg/m³, feed rate of 0.05 kg/s, concave width of 0.4 m, 15 % moisture content of unthreshed common beans and 2 kg mass of the threshing cylinder. In addition, the optimum power of 207 W for threshing corresponded to pegs` peripheral speed of 2 m/s, crop bulk density of 50 kg/m³, 0.02 kg/s feed rate, 0.6 m concave length, 15 % unthreshed crop moisture content, and 2 kg mass of the threshing cylinder. Finally, peripheral velocity and feed rate were the main contributing factors for maximum grain damage, threshing efficiency, and throughput capacity based on analysis of variance.