Gear Rolling for Production of High Gears

Abstract: Gears are used to transmit mechanical workfrom one point to another. They are widely used in different mechanisms and they are the most important components of a transmission system. Thus, it is important that they are manufactured with high precision to deliver the work with highest possible efficiency. The dominant gear production method is metal cutting, like hobbing. The gear manufacturing industry aims to replace their traditional production lines with greener processes and thereby urge engineers to think about using metal forming methods instead of the traditional metal cutting solutions when possible. Gear rolling is an interesting metal forming method that can be an alternative method to fabricate gear wheels.Research on gear rolling firstly came into interest around 2000. Very few papers are published that covers the development of the method and its limitations and advantages. Almost all of these publications considered rolling of gear wheels with small modules. The focus of this study will be on application of gear rolling for gear wheels with large module (over 3 mm) where the amount of deformation is much larger than found in previous studies.In this thesis the Finite Element Method has been used to simulate and predict the results of rolling of high gears. In addition to that experiments were performed to validate the numerical results and develop the modelling technique for further investigations. The main topic of discussion is about the gear quality as a measure of the success for the process. Extra attention has been paid to the effects of friction and process planning in the result of process loads and also on the gear quality.The thesis structure is based on four published papers, and some additional results from the experiments which have not yet been published. According to the results of these papers, the effect of friction and process parameters are recognized in the final product quality. It is shown that FEM has a great potential in order to model and analyze the gear rolling process. A new approach to combine numerical methods with quality measurement to predict the process outcomes is also presented. The results show that gear wheels with a module of 4mm reach an ISO quality level between 11 and 12. This is substantially lower quality than can be obtained with metal cutting operations. The results of this thesis can be used as the starting point for future research to optimize the quality of gear rolling for high gears.