| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 103 === Face milling is a mainstream mass production method for spiral bevel gears. Two types of tools were adopted in face milling method, including a milling cutter and a wheel. Because of difficulty in building a mathematical model of a milling cutter, the commercialized cutting simulation softwares apply an axisymmetric wheel instead of a milling cutter. This cutting method must be applied on a five-axis machine, however, five-axis movement is quite complex in processing. In order to remove the NC errors and avoid the collision between the cutting tool and machine axes or fixtures. A cutting simulation is required to verify the correctness of NC tool paths before cutting. To address the above issues, this study aims to develop a dedicated cutting simulation software for spiral bevel gears using a face-milling cutter.
A voxel-based method is adopted as a calculation core for the presented cutting simulation. The solid model of work gear is constructed using adaptive voxels, and the mathematical models of cutting blade surfaces are established. According to NC codes, the cutter positon relative to the workpiece is then determined use coordinate transformation matrix from the cutter coordinate system to the workpiece coordinate system. First, an interference detection between each cutting blade and the workpiece is made using oriented bounding box method. After limiting search scope for possible collision voxels, all vertices of candidate voxels are checked whether they are inside or outside the blade to implement cutting simulation. In order to improve the display resolution of produced tooth surface, the marching cube algorithm is adopted. Tooth surfaces of bevel gear are save as STL format for further investigation. Finally, an evaluation method for tooth surfaces deviations is applied to verify the correctness of the cutting simulation. And the material removal rate is examined for further NC programming optimization.
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