Modelling, simulation and compensation of thermal effects by hobbing gears

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Within the research project of the priority program 1480, the heat introduction into hobbed gears is investigated. The final aim is to enable the conditions for hobbing large gears without coolant. Due to the high heat quantity which is caused by dry hobbing the gear quality is deteriorating. For this reason the industry is using the nonproductive wet hobbing process. Compared to dry cutting, the coolant usage implies detrimental effects to environment and the manufacturing costs. To adopt the dry hobbing process for large gears, it is necessary to investigate the effect of the heat flux on the workpiece. Hobbing is oftentimes the last step in the process chain for large gears. In this step deviations in form and position could accrue and cannot be compensated anymore. For this reason special attention is needed herein.In the hobbing process, there are multiple gear teeths in contact. During this step, the chip geometry is different on every single tooth. This makes it difficult to carry out single tooth contact analysis on the workpiece. Thus an analogy trail is developed which enable the analysis of the single heat sources and simulation with FEM. In the second period of the project the results of the first period should be transferred to real hobbing. The experimental investigations are focused on thermal conditions in hobbing and its effect on the gear quality. The experimental investigations are focused on the thermal conditions in hobbing and its effect on the gear quality. At this platinum thermometer and an infrared camera are used. Furthermore the deformation of the gear is simulated by FEM to generalize the results. Afterward the gained knowledge will be transformed to a large gear in wind power industry. The experimental results of the IFQ serve to verify the simulation of the IWW.The method of FEM is used to describe the heat conduction and to calculate the local and global temperature gradient. The connection of the technological parameters and the transferability of changing parameters are assured by an analytical and semi-analytical model. Based on a verified and validated substitution model, which is created in the first period of the project, a transfer to real hobbing will take place. Thereby a calculation of the thermal deformation will be possible. This leads to the third project period where possibilities of compensations are identified.By the use of the simulated gear deformation, it is possible to estimate the feasibility of the process. Consequently different compensation can be used to avoid the thermal deviations on large gears.