Thread Content
Due to the special working environment and the complexity of the operating conditions, high requirements have been placed on the design of the belt conveyor and some key parts, especially the rollers, which are very important for the continuous and safe operation of the belt conveyor. Short damage to the roller will lead to downtime and renewal. Replacing the roller requires re-adjustment of the conveyor belt's traction, force adjustment and operation deviation. Therefore, damage to the roller will affect the safe operation of the conveyor and the continuous work of the working surface. 1. Structural characteristics of the new expansion-free sleeve roller. The structure of belt conveyor rollers commonly used in my country is that the roller and the connecting plate are installed with transition fit and keyed connection or are connected by an expansion sleeve. In practice, there are the following problems: When using key connections, the drum shaft usually needs to be keyed, which will inevitably destroy the overall strength of the drum shaft and shorten the service life of the drum. ； The use of expansion sleeve connection increases the cost of the entire drum ； In addition, technical requirements also need to be improved during installation. In response to the above situation, we have improved the design of the drum structure. The new drum hub and spoke plate are an integrated structure of steel castings. The hub and drum shaft adopt inner wall positioning of the hub (interference fit), and the bolt connection that is prone to failure is eliminated. The lower strength screw group connection of the transmission drum is eliminated. The transmission drum of this structure has significantly enhanced load-changing capabilities against impact and vibration after actual operation testing. 2. Calculation results and analysis. Due to the static analysis of the drum, the degree of freedom of the drum axis is relatively large, so the stress distribution of the drum shell and connecting plate is mainly analyzed. It can be seen from the stress distribution cloud diagram of the transmission roller and the displacement distribution cloud diagram of the transmission roller: (1) The stress of the transmission drum is mainly concentrated on the shaft section between the bearing and the connecting plate, the connecting plate web and the inner wall of the drum. The maximum equivalent stress is at the inner shoulder where the shaft and the bearing contact. According to the safety factor of the driving drum, which is generally 3 to 4, the strength of the drum shaft fully meets the strength requirements. Due to the uneven stress on the conveyor belt due to the deformation of the roller, stress concentration occurs in the roller weld, which is obviously within the strength requirements of the roller material. However, if the weld quality is not up to standard, there will be a large residual welding stress, which may cause the roller to crack. Therefore, the manufacturing of the driving roller must comply with relatively strict processing technical conditions, and the weld quality must be strictly controlled. (2) Due to the extrusion of the conveyor belt, the cylinder shell has a concave deformation, and the corresponding other half of the cylinder shell has a convex deformation, which is located in the center of the drum. Welding ribs along the axial or radial direction of the inner wall of the cylinder can effectively reduce the deformation of the cylinder shell and thereby reduce the stress concentration at the weld. 3. Optimal design of the transmission drum. Use the finite element method to optimize the structural size of the transmission drum. Through finite element stress and stiffness analysis, under the conditions of meeting the strength and stiffness of the transmission drum, try to minimize the important parameters of the drum and the thickness of the cylinder shell, the thickness of the connecting plate and the roller diameter. During the process of optimizing the design of the drum using the finite element method, other drum structural parameters remain unchanged. The optimization goal is to reduce the drum wall thickness to 20mm, but the deformation of the drum cannot be increased or even reduced, and the stress concentration of the weld at the connection between the connecting plate and the drum body does not increase. After calculation, it was found that the deformation of the drum increased significantly after the drum wall thickness became thinner, increasing by about 23%. Due to the reduction in drum rigidity, the stress concentration on the drum shaft was reduced, and the stress concentration at the drum weld increased. We can consider welding a radial reinforcing ring on the inner wall of the drum, and welding ribs along the axial direction to reduce the stress concentration of the drum and improve the overall strength of the drum. Finite element analysis calculation results show that the effect of reinforcing ribs on reducing drum deformation is very obvious, and can be reduced by about 30%. The stress concentration at the drum weld seam is significantly reduced, and has not changed much from before the drum wall became thinner. The purpose of optimizing the drum wall thickness is basically achieved. Obviously, the strengthening measures taken after the drum wall thickness becomes thinner are effective and can * * Reducing the wall thickness of the drum makes the drum lighter without affecting the actual strength of the drum. The new equal-strength drum adopts this strengthening measure. 4. Determination of the process characteristics and welding process of the new roller: (1)Welding method. First, heat the welding part and use CO2 and Ar mixed gas shielded welding for welding. Mixed gas shielded welding can overcome the shortcomings of CO2 gas shielded welding and ensure welding quality. When welding, the roller is placed on the roller frame to rotate, and the rotation speed can be controlled to ensure that the root of the weld can be penetrated without defects such as welding penetration. Welding can now be automated using specialized equipment. (2) Welding materials. Gas shielded welding materials: Welding wire H08Mn2SiA, diameter 12mm, shielding gas 25%CO2+75%Ar. (3) Preparation before welding. Remove water, rust, oil and other impurities within the groove and 50mm on both sides of the groove and on the welding wire. Flux 431 must be dried at 250℃ for 2 hours before use. (4) Drum assembly and bevel dimensions. ①When assembling the drum, the shaft, cylinder and connecting plate should be assembled at the same time. First install one connecting plate on the shaft, then insert the shaft into the cylinder, align the connecting plate with the cylinder and position weld it with a link plate, then install the other connecting plate on the other end of the shaft and fix the cylinder and the other connecting plate in the same way. ； ②Bevel size: The key to the groove size is the size of the gap and blunt edge. If the gap is small and the blunt edge is large, it will be difficult to penetrate during welding, and conversely, burn-through will easily occur. (5)Welding process parameters. The welding seam is formed by gas shielded welding in one step, and reverse welding has excellent results. (6) Tempering after welding. Since the drum shaft has been tempered, tempering of the entire drum will reduce the performance of the shaft, so only partial tempering of the welds can be performed. After the weld is tempered for 24 hours, the weld is inspected for flaw detection according to the design standards, and the quality of the weld meets the design requirements. The emergence of finite element theory and various finite element analysis software allows conveyor designers to basically grasp the force and deformation of the drive roller without doing a lot of calculations and research on the force of the transmission roller. They can also use the finite element calculation results to find out the weak links in the design, and then achieve the purpose of improving the design of the roller. In this regard, we designed a new type of roller, formulated various technical indicators of the roller based on the conveying capacity, length, and belt speed of each belt conveyor, optimized various technical parameters, reduced the cost of the roller, and increased the service life of the roller.