Design and experiment of pneumatic needle suction device for precision seeding of small particle size sprout seeds

Aiming at the lack of mechanized precision seeding devices for multi-row parallel sowing of small-sized sprouting seeds, as well as issues such as poor uniformity and seed damage associated with manual sowing, this study designed a pneumatic precision seeding device. The working process of the seeding device was explained, a kinetic model for seed adsorption was established, and CFD simulation experiments were conducted to determine the main structures and parameters, including the vibrating seed-feeding device, oscillating cylinder, seedling tray conveying device, and tray stacking mechanism. Using vacuum pressure, suction hole diameter, and pneumatic vibrator frequency as experimental factors, single-factor tests and a quadratic orthogonal composite test with three factors and three levels were carried out. Single-factor test results indicated that for Toona sinensis seeds, better sowing performance was achieved with a suction hole diameter of 0.6～1.2 mm, a vibration frequency of 8～16 Hz, and a vacuum pressure of 3～12 kPa. For alfalfa seeds, better performance was obtained with a suction hole diameter of 0.4～1.2 mm, a vibration frequency of 8～12 Hz, and a vacuum pressure of 2～6 kPa. Quadratic orthogonal test results showed that the optimal sowing performance for Toona sinensis seeds was achieved at a vibration frequency of 12 Hz, a suction hole diameter of 0.9 mm, and a vacuum pressure of 7.5 kPa, while for alfalfa seeds, the optimum was at a vibration frequency of 10 Hz, a suction hole diameter of 0.6 mm, and a vacuum pressure of 5 kPa. Bench test results under the optimal parameter combinations showed that for Toona sinensis seeds, the qualified seeding rate was 95.48% and the miss-seeding rate was 1.70%; for alfalfa seeds, the qualified seeding rate was 92.10% and the miss-seeding rate was 2.30%, meeting the requirements for precision sowing of small-sized sprouting seeds. The research findings can provide a reference for the structural optimization of seeding devices for small-sized sprouting seeds.