Design of Gear Hobbing Processes Using Simulations and Empirical Data

Gear Hobbing is one of the most productive manufacturing processes for pre-machining cylindrical gears. The process design as well as the tool selection is often based on experience or is limited to an iterative procedure. Existing methods for process and tool design are limited regarding the size of the gears and the process parameters.The objective presented in this paper is to support the process design by suggesting process parameters. To achieve this goal, a simulation for continuous gear hobbing was developed. By calculating planar intersections of transverse sections of both gear and tool, the generated chip geometries are determined. Due to the general approach of positioning tool and workpiece in the program, all continuous processes with defined cutting edges can be simulated. The generated chip geometries are analyzed and characteristic values for each position of the tool are defined. Beside the chip geometries, other parameters such as working areas and the length of axis movements are calculated too.Since the simulation process is time-consuming, it is not possible to calculate each hobbing process for different designs. Also, the simulation program cannot be implemented into the machine control due to the needed computing capacity. Thus, a large amount of hobbing processes with varying gear geometries as well as different tools with the corresponding profiles are calculated in advance. By the use of regression analysis, the results of these variations are transferred to approximation formulas afterwards, which are easy to calculate and to implement into other software products.To support the tool and process design, existing hobbing processes will be simulated with the help of the developed manufacturing simulation and the results will be stored in a database. By comparing the results of the approximation formulas with the values in the database, it is possible to evaluate a given process.