Design and test of tilt dise-type fine and small-amount seed metering device for foxtail millet

Abstract: In order to solve the difficulties of sowing for small grain seeds, such as foxtail millet, we firstly study the agricultural requirements of precision drill of millet without thinning out seedlings. After analyzing the advantages and disadvantages of different seeding devices, we design a kind of tilt dise-type fine and small-amount seed-metering device for foxtail millet. We measure the shape and dimension of the millets with the microscope using the projection method, and the friction coefficient of millet with different materials as requested by the national standard of China. We analyze the motor process of millet, which helps us design the structure of this device. It is mainly made up of filling dise, shell, discharging dise, elastic flipping device and drill shaft. It has many advantages. Its structure is simple, and its working principle is reliable. Its working position tilt is from 45° to horizontal direction. The overflowing seeds from filling holes are flexibly cleaned under the action of gravity, so they will not be damaged. There are 36 filling holes in the filling dise, and they are uniformly distributed on the circumference of filling dise. Matched with filling holes, there are 36 seeding grooves in the discharging dise, which are uniformly distributed on the circumference of discharging dise. The filling dise is above the shell, and the discharging dise is below the shell, both of which synchronously rotate. There is a passing hole between them in the shell. The millets fall in the filling holes, and revolved around the drill shaft together with filling holes. When they arrive at the passing hole, the millets leave the filling holes, then pass through the passing hole and enter the seeding grooves. The millets continue to revolve around the shaft together with the grooves. There is a dropping hole at the bottom of the shell. Before they arrive at it, the millets move to the end of the grooves. When they arrive at the dropping hole, the millets leave the groove, pass through the dropping hole, and fall into the seeding tube. According to the movement characteristics of millets, on the premise of not damaging them, we design the shapes and dimensions of the filling hole, seeding groove, passing hole and dropping hole. This device is expected to seed 2-3 millets from every seeding groove, and the intervals of millets are kept steady on the soil. We especially design an elastic flipping device to flip the millet stuck in the filling hole out of it, which is installed on the upper boss above the passing hole of the shell. We design the fit clearance of 0.2 mm between filling dise, discharging dise and shell simultaneously, thus eliminating the friction between them. In order to test the performance of this device, we use 6 indices from the national standards of China. They include the percentage of damaged seeds, variability coefficient of steadiness of total seeding quantity, qualified index of hill spacing, repeated sowing index, miss-seeding index and variability coefficient of qualified hill spacing. We design and conduct the experiments of the steadiness of total seeding quantity and the uniformity of seeding rate with this device. We also measure the percentage of damaged seeds discharged from this device. The results show that the variability coefficient of steadiness of total seeding quantity is less than 0.7%, the qualified index of hill spacing is greater than 86%, the repeated sowing index is less than 12%, the miss-seeding index is less than 7%, the variability coefficient of qualified hill spacing is less than 5%, and the percentage of damaged millet is less than 0.05%. All the indices meet the requirements of the industrial standards of China. It will provide a theoretical reference for the design and analysis of fine and small-amount seed-metering device for small grain seeds.