# Orbital-Based Automatic Multi-Layer Multi-Pass Welding Equipment for Small Assembly Plates
## 2 Design and Analysis of Rail-Mounted Automatic Welding Equipment
### Static Analysis of the Equipment's Core Mechanisms
This off-center arrangement prevents interference between the wire feeder and the communication and power cables of the robotic arm during the operation of the track-based equipment, ensuring greater flexibility in the movement posture of the welding robot and providing sufficient workspace. A load shift analysis is conducted below. To reduce computational errors from excessive workload, the model is simplified for analysis, with the finite element mesh model shown in Figure 7.  
At one end of the robotic arm mounting base, the load includes its own body, the robotic arm, the welding torch module, and the vision module, totaling 21 kg. At the wire feeder end, the load includes its body and the supporting rail section, totaling 20.3 kg. The loads at both ends are directed vertically downward, and the distance from the robotic arm's center of mass to the center of the rail cart is 682 mm. Therefore, an eccentric concentrated load is applied to the model; as shown in Figure 8a, corresponding normal pressures and gravitational loads are applied to both ends. The deformation results of the robotic arm mounting base are shown in Figure 8b; the maximum deformation is 0.23 mm, occurring at its upper end surface. The overall equivalent stress is depicted in Figure 8c; the maximum equivalent stress is 37.285 MPa, occurring at the junction between the robotic arm mounting base and the rail cart. The maximum equivalent stress at the rail is 26.747 MPa. Both values are much lower than the material's yield strength of 353 MPa, satisfying the structural strength requirements. The overall deformation of the simplified eccentric load mechanism is shown in Figure 8d. Experimental results confirm that this arrangement is reasonable and operates stably. The finite element mesh model of the rail section is shown in Figure 9. The rail section has a length of 500 mm and is made entirely of aluminum alloy. As illustrated in Figure 10a, a downward vertical pressure of 9.756 MPa is applied to the aluminum alloy rack of the rail section. The deformation diagram of the rail section is shown in Figure 10b, where the model's maximum deformation is 0.09 mm. The local and overall equivalent stresses are presented in Figures 10c and 10d, respectively. The maximum equivalent stress is 269.96 MPa, located at the guide rail position of the rail section, reaching the yield strength of 270 MPa for 6063-T5 aluminum alloy. At this point, the maximum equivalent stress for aluminum alloy 6061-T6 is 50.086 MPa, which does not reach its yield strength of 275 MPa. In the simulation analysis for the application conditions or the actual engineering application of the mechanism, if the stress on the rails approaches their maximum allowable range, the material can be replaced according to the corresponding performance requirements and safety demands, retaining a certain safety margin in the selection of material properties. According to safety regulations, it is necessary to prevent deformation or even fracture of the rails caused by overload on their surface to avoid derailing or the equipment running off the track due to rail deformation or uneven stress, which could affect equipment operation and processing. Figure 7: Rail cart grid division model diagram. (**a**) Finite element module division diagram. (**b**) Finite element mesh division diagram. The robotic arm mounting base is made entirely of aluminum alloy, and its finite element mesh model is shown in Figure 11.  
Figure 8: Simplified mechanism bias load analysis diagram. Figure 10: Track section analysis diagram. Figure 6.0 Track section grid division model diagram. (**a**) Finite element module division diagram. (**b**) Finite element mesh division diagram. As illustrated in Figure 12a, a pressure of 2.62 MPa is applied to the back surface of the robotic arm mounting base, directed perpendicularly outward. The deformation diagram of the robotic arm mounting base is obtained, as shown in Figure 12b, where the model's maximum deformation is 1.509 mm.