Design and Experiment of Substrate Grass Seed Blanket Extrusion Device

Abstract

After corn straw and livestock manure are fermented and decomposed, grass seeds are added. The substrate grass seed blanket is made by screw extrusion, applied to park greening, square greening, protective greening, and residential area greening. With this device, the purpose of reducing the labor force and improving space utilization rate can be achieved. The working principle of the substrate grass seed blanket extrusion device is mainly described, and the extrusion process is analyzed including: compaction and filling stage, surface deformation and compaction stage, plastic deformation stage, and molding stage. The main experimental factors are determined through theoretical analysis of screw size and working parameters, including screw pitch, screw length, screw diameter, and screw speed. Using the EDEM simulation analysis method, taking the quality of extruded particles and the uniformity of grass seed mixing as test indexes, and under the condition of the same extrusion time of 30 s using Design-Expert software to carry out an orthogonal quadratic rotation combination test, a significant regression model was obtained. The effects of different parameters and extrusion conditions on grass seed blanket forming influence were studied by response surface analysis. The optimal working parameters were obtained: screw speed 250 r·min−1, screw pitch 120~80 mm, screw diameter 240 mm, and screw length 400 mm. With the same extrusion time of 30 s, extruded pellet mass was 2620 g, calculated mass flow rate was 131 g/s, and the grass seed mixing uniformity was 92.35%. Under the optimal simulation conditions, the prototype was manufactured, and the actual verification test was carried out. The errors between the measured values of extruded substrate quality and grass seed mixing uniformity and the simulation test results were 3.4% and 2.5%, respectively, which met the requirements of the grass seed blanket extrusion molding device.