An Accurate Method of Generating Tool Paths for Helical Gears with Crowning Modifications Using a 5-axis CNC Machine
To manufacture gears, special machine tools and corresponding processes, such as hobbing, shaping, planing, profile milling, and broaching, are usually needed. However, the huge investment in such gear machining is prohibitive for manufacturers, which only produce the gears in small batches on an annual basis. To overcome this economic problem in the manufacturing of gears, standard 5-axis CNC machines were proposed as an alternative tool for machining them, and a few approaches were presented to implement this gear manufacturing method. However, machining helical gears with crowning or other modifications has been little studied. This paper proposes an accurate method to manufacture helical gears with crowning modifications using a standard 5-axis CNC machine tool. As gear roughing process, milling using an end mill was selected, where the tool movement follows the generation principle. By incorporating crowning modifications into the tool’s movement, an accurate tool path generation method was developed. A CAM software written in C++ was developed to generate, visualize, and simulate the tool path for machining the gear according to user-defined parameters. The tool path was subsequently post-processed into NC code to run on a CNC machine. To validate the generated NC code, an internal helical gear with crowning modification was machined on a conventional 5-axis CNC machine. The machining results confirmed that the proposed method is feasible. The machined helical gears will be measured using optical and tactile CMMs to determine their deviation parameters.
Authors: Fei Shen, Luis Vega, Mohammadrafi Marandi, Christoph Kossack, Joshua Tarbutton, Gert Goch
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