Optimization of working parameters of cleaning system for master-slave residual plastic film recovery machine

Abstract: Plastic film has been widely used to mulch soil in croplands, but its recycling rate is less than 60%. Since natural degradation of plastic film is slow, accumulative use of plastic films has resulted in soil structure degradation and environment deterioration. Recycling the film residuals is hence mandatory. Manual picking is labor intensity and inefficient, and mechanical recycling is thus called. Most machines available on market are unable to separate the film residuals from straw and large soil particles during pick-up process. To alleviate this problem, we designed and tested an machine equipped with an improved cleaning system. We optimized the working parameters of the system in attempts to improve the residual recovery efficiency. Analysis of the structure of the cleaning system, its working principle and conditions, as well as the factors affecting the machine operation revealed that the most important parameters were the advancing speed of the machine, the speed of the film-conveyer, position of the pick-up drum and the speed of the secondary impurity-conveyer. We investigated the recovery rate of the film residuals, rate of separating the film residuals from the straw, and transport efficiency of the impurity, using the regression orthogonal combination tests with four five-level factors. The response surface of the testing results was analyzed using the design-expert software, and the relationship between each impacting factor and the testing index was also analyzed. The results showed that the main and secondary factors affecting the picking-up rate were position of the picking drum and the advancing speed of the machine, and that the factor affecting the separation rate mostly was the speed of film transportation followed by rotating speed of the impurity conveyer. The transport efficiency was affected mostly by the rotational speed of the impurity conveyer, followed by location of the pick-up drum, speed of the film-conveyer and advancing speed of the machine. The regression model was optimized with multiple objectives, and the optimal working parameters for the cleaning system are: Advancing speed of the machine and equipment: 1.26 m/s, speed of the film transporter: 1.55 m/s, position of the pick-up drum: -17 mm (taking the center of the hole in the supporter and the center of the picking-drum in the vertical direction as the origin, adjusting 17 mm to the forward direction of the machine), speed of the secondary impurity conveyer: 205 r/min. Calculated using these optimal parameters, the pick-up rate of the film residuals was 90.19%, the separation rate of the film residuals from the impurities was 92.21%, the impurity transport efficiency was 89.6%. We verified these against field experiments, and the results showed that the picking-up rate was 91.54%, the separation rate was 90.37%, and impurity transport efficiency was 88.4%. This paper offers references to improving quality of the cleaning system in plastic-film pick-up machine.