Design and parameter optimization of arc tooth and rolling bundle type plastic film residue collector

The application of plastic film mulching technology has brought considerable economic benefits to China's agricultural production, but also caused a series of pollution problems. Due to the incomplete recovery and cumulative accumulation of plastic film residuals over years, the soil permeability to water and the soil structure are poor, seriously affecting the sustainable development of China’s agricultural economy. The main cause of such soil pollution is that the polyethylene film used in agricultural production in most areas of China is thin, the film covering time is long, and the recovery rate is low, and as such a large number of residual films remains in the soil tillage layer. Among them, the proportion of the buried edge film under the surface is 7% - 16%. The edge film is bound to the soil, which is easy to tear with the surface film when recycling, which leads to the difficulty of the recovery of the edge film. Researchers of agricultural machinery in China have developed a variety of plastic film residue collectors, including nail-tooth, telescopic rod-tooth, clip the hold type, spring-tooth and so on. However, there are many problems, such as complex structure, poor reliability and low recovery rate. At the same time, the research of the plastic film residue collector mainly focuses on the surface film pickup, while the research on the side film pickup and unloading is insufficient. Aiming at the problems of the existing plastic film residue collector, an arc tooth and rolling bundle type plastic film residue collector was designed in this study. According to the force of its work piece and the analysis of the motion track of the pickup mechanism, the key components such as the pickup shovel, the picking-up film mechanism and the unloading film mechanism were researched. In order to simulate the deformation and stress of nail teeth, plastic film and soil in the process of film-picking nail teeth fixing was used to guide the design of collector. Nonlinear finite element dynamics simulation analysis of film picking process of arc tooth and rolling bundle picking-up mechanism was done by use of ANSYS software. The simulation results showed that in the process of picking up plastic film, the end of nail teeth had the largest deformation. The maximum deformation of plastic film occurred at the contact position with the end of nail teeth. The deformation of soil disturbed by nail teeth was small. Using Box-Benhnken's central combination method, three-factor and three-level quadratic regression tests were carried out for the influence of the machine advancing velocity, the angle between the shovel wing and the shovel handle, and the depth of the nail teeth into the soil. Response surface regression model was established based on the carryover edge film rate, picking up film rate and unloading film rate, and the influence trend of each factor on the test index was analyzed. In order to improve the recovery rate of residual film residue, the influencing factors were optimized comprehensively. The experimental results showed that the significant factors affecting the rate of rimming film were as follows: the angle between the shovel wing and the shovel handle > the depth of the nail teeth into the soil > the machine advancing velocity. The significant factors affecting picking up film rate were as follows: the machine advancing velocity > the angle between the shovel wing and the shovel handle > the depth of the nail teeth into the soil. The significant factors affecting unloading film rate were as follows: the machine advancing velocity > the depth of the nail teeth into the soil > the angle between the shovel wing and the shovel handle. Finally, the optimum parameters were determined as follows: the machine advancing velocity was 4 km/h, the angle between the shovel wing and the shovel handle was 90°, and the depth of the nail teeth into the soil was 55 mm. Field experiments were conducted under these conditions and the following data were obtained, the carryover edge film rate was 93.5%, the picking up film rate was 87.4% and the unloading film rate was 87.1%, and the error between the experimental results and the optimized theoretical values was less than 4 percentage point. This research results provide theoretical basis and technical reference for structural design and working parameters selection of plastic film residue collector.