Design and test of the T-shaped hole of centrifugal high-speed maize precision seed metering device

Agricultural production has been dominated by mechanization in recent years. High-speed precision seeding can fully meet the requirements of high-efficiency mechanized planting. There is a high demand for the stable and excellent operational performance of the precision seed metering device. In this study, a T-shaped hole was designed to update the existing centrifugal maize precision seed metering multiple seeding. The hole-shaped symmetric tab structure was also proposed to reduce the probability of maize seed side-by-side filling. A systematic analysis was made to clarify the influence of the structural parameters in a T-shaped hole on the process of sowing. The size of the maize seed was combined to determine the values of some structural parameters of a T-shaped hole. The range of the factors was selected for the subsequent orthogonal tests. Specifically, the length of the front, the rear inclination angle, and the inclination angle of the bottom inclination angle were from 8.64 to 15.36 mm, 41.64° to 48.36°, and 64.59° to 81.41°, respectively. A three-factor three-level quadratic orthogonal rotational regression test was conducted on EDEM software using the structural parameters as test factors, while the qualified, multiple and leakage indexes as evaluation indexes. ANOVA and response surface optimization were then performed on Design Expert 13 software. A combination of optimal structural parameters was achieved in the T-shaped hole: the length of the front was 9.31 mm, the rear inclination angle was 43.37°, and the inclination angle of the bottom inclination angle was 70.5°. The predicted qualified, multiple and leakage indexes were 95.44%, 0.9% and 4.48%, respectively. Three groups of simulations were carried out to verify the optimization under the same conditions. At the same time, the qualified, multiple and leakage index of seed metering device were 94.03%, 1.72% and 4.25%, respectively. There was close to the predicted value, indicating the accurate optimization of quadratic orthogonal rotary regression. A bench test was carried out to verify the reliability of the simulation and the effectiveness of T-shaped hole, in terms of reducing multiple indexes. The qualified index of the seed metering device was 94.54% when the operating speed was 18 km/h. The relative error with the simulation was 0.54%, indicating the reliability of simulation optimization. When the working speed is 12～21 km/h, the qualified index of T-shaped hole is not less than 94.36%, the multiple index is not higher than 3.26%, and the leakage index is not higher than 3.60%, and the average qualified index of T-shaped hole is 94.77%, which is improved by 3.13 percentage points compared with rectangular shaped hole, and 1.80 percentage points compared with horseshoe shaped hole; the average mutiple index of T-shaped hole was 2.06%, a decrease of 3.41 percentage points compared to rectangular shaped holes and a decrease of 2.49 percentage points compared to horseshoe shaped hole.