Structure parameter optimization and bearing limit analysis of the expansion unit of three-roller tube expander

According to the performance requirements of expansion tools in bellows mechanical expansion process, this paper studies and analyzes the critical technical issues for the structure design of three-roller tube expander. It is indicated that the expansion unit structure is the main influencing factor for the performance of three-roller tube expander. The major design parameters and key parts of the expansion unit structure of 12 1/4" three-roller tube expander was optimized by theoretical analysis and finite element numerical simulation method. The bearing limit of three-roller tube expander was also studied by numerical simulation method. Results from study show that the required expansion force increases when the taper angle of the roller outer surface gets larger, taking the axial expansion force as the quantitative indicators. It is suggested that the roller tape angle of the expansion unit should be in the range of 9-12 ° considering the proper length of the roller and the un-self-locking tube expansion process. The required expansion force of the bellows first decreases and then increases when the gage length of the expansion unit becomes longer. The optimal value of the gage length is 50mm considering the proper length of the roller. Multiple sets of needle roller bearing are adopted to improve the bearing system loading capacity of expansion unit. In order to improve the loading capacity and abrasive wear resistance capacity of the thrust bearing, polycrystalline diamond is used as the wear-resistant material on the friction surface of the sliding trust bearing. The reliability of the tube expander under various working conditions is verified according to the bearing limit analysis of the tube expander.

Methods
Calculated by numerical simulation.