# Design, Simulation and Experimentation of a Polythene Film Debris Recovery Machine in Soil
## 3 Results  
### Effect of the Different Elastic Teeth Structures on the Recovery Rate of PF  
The experimental results obtained from the present study were represented by curved surfaces. The response of the interaction between the rotating speed of the conveying device and the distance between the elastic teeth to the recovery rate of the residual PF was analyzed under the condition that the elastic teeth were A-shaped, B-shaped and C-shaped structures, respectively. As could be seen in Figure 5, under the same conditions, the structure type of the elastic teeth directly affected the experimental results of the recovery rate of the residual PF. As is shown in Figure 5c, when the rotating speed of the conveying device and the distance between the elastic teeth are 74.08 rpm and 59.61 mm, respectively, the maximum recovery rate of PF is 88.62%. The rotating speed of the conveying device, the distance between the elastic teeth and the type of elastic teeth had a significant influence on the recovery rate of residual PF in the soil. With the increase in the conveying device's rotational speed and the distance between elastic teeth, the recovery rate of the residual PF reached the maximum value and then decreased. Compared with the test results of Figure 5a-c, it could be concluded that the recovery rate of residual PF of C-shaped elastic teeth was the highest, and the recovery effect of residual PF was the best. Figure 4: Shows the treatment process for measuring quality of residual PF: **(a)** selecting an area of 1 m\({}^{2}\) in the test site and collecting the residual PF in the soil within 150 mm depth, **(b)** cleaning the residual PF, **(c)** drying the residual PF after cleaning, **(d)** measuring the quality of the residual PF and obtaining experimental data. Under the condition of different elastic teeth types, the response regularity of the interaction between the rotating speed of the conveying device and the distance between the elastic teeth to the recovery rate of the residual PF could be clearly observed by using the three-dimensional surface diagram. Effect of the Rotational Speed on the Throwing Horizontal Distance of PF at Different Inclination Angles  
Figure 6 explains that the throwing horizontal distance of PF is directly affected by the rotational speed and inclination angle of the conveying device. Under the condition of constant inclination angle between the conveying device and the horizontal plane, the horizontal distance of the residual PF thrown by the conveying device also increased with the increase in the rotational speed of the conveying device. As is represented in Figure 6, the horizontal distance to which PF was thrown also increased with the increase in the inclination angles of the conveying device from 25\({}^{\circ}\) to 35\({}^{\circ}\), but it began to decrease as the inclination angle increased from 35\({}^{\circ}\) to 55\({}^{\circ}\). The horizontal distance to which PF was thrown increased from 331 mm to 893 mm, 610 mm to 1156 mm, 433 mm to1056 mm and 224 mm to 776 mm when the conveying device's  
Figure 5: Effect of the conveying device’s rotational speed (rpm) and the distance between elastic teeth (mm) on the recovery rate of PF (%) at three types of elastic teeth, (a) A, (b) B and (c) C.  
Figure 6: Effect of the conveying device’s rotational speed (rpm) on the throwing horizontal distance of PF (mm) at different inclination angles between conveying device and the horizontal plane (\({}^{\circ}\)). rotational speed increased to 30 rpm, 50 rpm, 70 rpm and 90 rpm at inclination angles of 25\({}^{\circ}\), 35\({}^{\circ}\), 45\({}^{\circ}\) and 55\({}^{\circ}\), respectively, which was consistent with the results of previous field experiments. The bigger the horizontal distance of the residual PF thrown by the conveying device, the better the separation effect of the residual PF and impurities.