# Research on the Structure of an Underground Irrigation Composite Pipe-Forming Device
## 3 Design of Extrusion Parts
### Determination of Parameters of Extruded Parts  
As an essential parameter of extrusion, the diameter of the winch blade directly affects the size and output of the device. To determine the diameter and size of spiral auger blades, factors such as the material conveying type, production capacity, and layout and structure of the extrusion-forming device components need to be considered. The formula for the diameter of the winch blade is [19]:  
\[D=K\bigg{(}\frac{Q}{\phi\lambda\epsilon}\bigg{)}^{\frac{2}{\phi}} \tag{1}\]  
where \(K\) is the comprehensive characteristic coefficient of material, the value of which is 0.05; \(Q\) is the displacement per unit time for the auger conveyor; \(\phi\) is the filling factor, the value of which is 0.3; \(\lambda\) is the material density, the value of which is 0.15; \(\epsilon\) is the inclined conveying coefficient, the value of which is 0.46. In order to ensure the consistency of the mixed material feed rate of the extrusion molding device and the forming rate of the straw composite pipe, the displacement per unit time of the screw conveyor should be equal to the feed rate. According to the GB/T24675.6-2009 \"Protective Tillage Machinery Straw Crushing and Returning Machine\" field test. Before the test, a distance of 10 m is measured with a tape measure and a certain stable area is left before the 10 m measurement. After starting the equipment, the speed of the tractor will remain stable after running in the stability zone for a period of time. When entering the 10 m measurement area, the unit's running time is measured with a stopwatch, and finally the tractor's driving speed is obtained. The test showed that the amount of straw picked up by the straw tetramer with a width of 100 cm was 1394.72 g per 100 cm. Since  
Figure 1: Structural diagram of a compound pipe-forming device for underground irrigation: (**a**) top view of the device; (**b**) left view of the device: (1) three-phase asynchronous motor; (2) driving pulley; (3) belt; (4) driven pulley; (5) reducer; (6) coupling; (7) driving gear; (8) driven gear 1; (9) driven gear 2; (10) feed barrel; (11) rotating mixing shaft 1; (12) mixing plate; (13) rotating mixing shaft 2; (14) mixing plate; (15) winch shaft; (16) auger blade; (17) housing; (18) support frame; (19) flange; (20) discharge drum. the amount of straw picked up accounted for 5% of the total material, it can be calculated that the total mass of the mixed material was 27,894.40 g. According to the different driving speeds of the tractor, different material feeding quantities can be determined, i.e., \(Q_{1}\) = 3.5 t/h, \(Q_{2}\) = 4 t/h, and \(Q_{3}\) = 4.5 t/h. The above can be substituted into Formula (1) to get \(D=0.05\times\left(\frac{Q}{0.3\times 0.15\times 0.46}\right)^{\frac{2}{3}}\), \(D_{1}\) = 0.389 m = 389 mm, \(D_{2}\) = 0.410 m = 410 mm, \(D_{3}\) = 0.430 m = 430 mm. The diameters of the winch blades were \(D_{1}\) = 390 mm, \(D_{2}\) = 410 mm, and \(D_{3}\) = 430 mm. The screw diameter affects the size of the screw reamer shaft diameter, and the screw shaft diameter and the screw diameter together affect the lift angle of the reamer blade. These two aspects together determine the speed, size, and direction of movement of the mixture in the spiral winch conveyor. Thus, the reasonable numerical relationship between the spiral shaft diameter and the screw diameter should take into account the friction between the spiral surface of the winch blade and the extruded material being conveyed, as well as the velocity component of the mixture. In general, the calculation formula for the shaft diameter of a winch is \(d=(0.2\sim 0.35)D\). The value is 0.2, so \(d_{1}\) = 78 mm, \(d_{2}\) = 82 mm, and \(d_{3}\) = 86 mm. The pitch of the screw not only affects the spiral lift angle but also affects the slip surface of the material transported under a certain filling factor; therefore, the size of the pitch directly affects the conveying state of the mixed material.