# Design, Simulation and Experimentation of a Polythene Film Debris Recovery Machine in Soil
## Materials and Methods  
### Materials  
The experiment was conducted during the cotton sowing season in Xinjiang (April-May 2020). The test site was Aksu City of Precision Agricultural Machinery Manufacturing Company in Xinjiang Uygur Autonomous Region, China (41\({}^{\circ}\) N, 80\({}^{\circ}\) E, elevation = 1105 m). The light intensity in Xinjiang is sufficient and suitable for growing cotton. In 2020, the planting area of cotton covered with PF in Xinjiang was 2.502 million hm\({}^{2}\), accounting for more than 80% of the cotton planting area in China [23]. The experiment was carried out in a cotton field after ploughing, at which time the cotton straw was crushed and buried in the soil as an organic fertilizer. PF was more difficult to recycle and contained a lot of soil and other impurities, because it was broken into smaller pieces in the soil. The soil moisture content and broken rate were 9.67% and 70.56%, respectively, and the thickness of residual PF was 0.008 mm. The length of cotton stalks in the plough layer were about 10 mm to 50 mm, and the moisture content was about 14.75% [26]. In the above-mentioned experimental environment, the PF debris collector of the plough layer was tested and evaluated. The PF debris collector used in the current work had dimensions of 3500 mm, 1500 mm and 1200 mm for its length, height and width, respectively, as shown in Figure 1.  
Figure 1: Designed model (**a**) and prototype (**b**) of the PF debris collector, consisting of the following functional parts: soil shovel (1), suspension frame (2), power transmission system (3), conveying device of chains and elastic teeth (4), frame of the PF collector (5), PF recycling box (6) and device for separating residual PF from soil and impurities (7). The conveying device of chains and elastic teeth consisted of elastic teeth, chains and steel bars that were fixedly connected with chains. Elastic teeth were installed on the steel bars at a certain distance, but the elastic teeth could not move in the axial direction and the circumferential direction could rotate (Figure 2). Three types of elastic teeth made of steel with a diameter of 5 mm were designed in this paper, as shown in Figure 3a-c. Residual PF, soil and impurities were shoveled into the conveying device of chains and elastic teeth. Residual PF and larger soil particles were transported back to the separator by the elastic teeth, but small soil particles and impurities could fall to the surface of the cotton field through the gap between the elastic teeth. The mechanism for separating residual PF from soil and impurities was composed of a conveyer belt, supporting roller and roller chain system, and the rotating direction of the conveyer belt was counterclockwise. The separation of residual PF from soil and impurities was realized by the difference in the falling velocity of residual PF and soil particles and impurities on the belt. The PF recycling box, installed at the rear and lower position of the conveyor chain, was a rectangular screen box with dimensions of 500 mm \(\times\) 1500 mm. After the separation of PF debris entering into the rectangular screen box, the smaller size of impur  
Figure 3: Designs of three types of elastic teeth, A, B and C, as shown in Figure (**a–c**). Figure 2: Designed model (**a**) and prototype (**b**) of the conveying device, showing the chains (1), steel bars (2) and elastic teeth (3). The mainframe was constructed from 60-mm square steel pipes to carry the power transmission system, soil shovel, conveying device of chains and elastic teeth and mechanism for separating residual PF from soil and impurities. The power was transmitted from the tractor (55 kW) through the reducer and a V-belt to the conveying device of chains and elastic teeth, which was transmitted through the roller chain system to the separating unit. The conveying device's rotational speed was determined by a digital tachometer with an accuracy of \(\pm\)0.05% + 1, ranging from 1 to 19,999 rpm.