Study On Forming Mechanism And Process Optimization For Cup-shaped Thin-walled Inner Gear Spinning

In traditional technology, cup-shaped thin-walled inner gear is produced by stamping two pieces of the part separately, and then welding together. Spinning technology changes this status and it overcomes demerits of traditional cutting process, such as complicated process, low precision and high cost. During inner gear spinning, the deformation behavior of metal is very complex due to the partial thickening (in the area of gear-tooth) and thinning (in the area of tooth-groove), which is greatly different from that of the conventional and power spinning technologies. So the research work on inner gear spinning is of significance not only for the manufacturing of inner gear, but also for the development of spinning technology.The research mainly focuses upon the deformation mechanism, relationship among forming parameters, and forming process optimization of inner gear spinning. This project was financially supported by National Natural Science Foundation of China"Forming mechanism and application research on cup-shaped thin-walled inner gear by spinning"(50475097), Provincial Natural Science Foundation of Guangdong"Forming mechanism and application research on cup-shaped thin-walled inner gear by spinning"(04105943), and Industrial Science and Technology Development Program Foundation of Guangdong"Research and application on key technology and equipment for spinning instead of cutting in gear manufacturing field"(2006B11901001).Based on the analysis on the difficulties in establishment of numerical simulation model for inner gear spinning and the basic theory of large deformation elasto-plastic finite element, MSC.MARC is chosen as the FEA software. And the key technologies, such as the definition of contact and friction, meshing problem, and convergence criterion have been discussed. To solve the problems of mesh distortion and low computing efficiency in analysis, an effective solution is put forward.Based on the 3D elasto-plastic simulation results, the researches of the deformation mechanism and the influence of geometric and processing parameters on gear tooth forming have been carried out. It mainly focus on the metal flow rule during inner gear spinning, and the forming accuracy of spun part and forming defects have also been predicted, which establish a sound foundation for the practical application of the inner gear spinning technology.Various experimental verifications have been conducted for the simulation analysis results. These processing experiments mainly focus on the forming characteristics of spun part, and the influence of geometric parameters of roller and gear tooth on inner gear spinning. In addition, the technologies of experiment design and variance analysis are employed to analyze the processing parameters of inner gear spinning and the significant (interaction) factors for inner gear spinning are selected from various parameters. The simulation results conform well to the experimental ones. It shows that the numerical simulation model for inner gear spinning and relevant analysis are reasonable.To solve the problems occurring in original forming process, optimized forming processes are put forward. Two-pass spinning is adopted to solve the demoulding problem in involute inner gear spinning and stagger spinning is employed to solve the problems of the overload and poor surface quality in straight profile inner gear spinning. And the feasibility of these optimized forming processes is verified by the processing experiment.Optimization technologies are introduced to processing parameters selection. For the single-objective optimization problem of involute inner gear, a mathematical model is established by surrogate models-based methods, which indicates the relationship between forming quality of inner gear and processing parameters. For the multi-objective optimization problem of straight profile inner gear, the optimizated reduction distribution is determined by the gray relational grade obtained from the gray relational analysis. Based on the optimized processing parameters obtained from optimization design, the inner gear spun workpieces are produced successfully. It establishes a sound foundation for the practical application of the inner gear spinning technology.