Transactions of Nanjing University of Aeronautics & Astronautics
A New Manufacturing Method for Hourglass Worm Gear Hob Based on a Semi-automatic CAD
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Abstract:
The top relief surfaces of an hourglass worm gear hob are ground manually in the traditional manufacturing process， which cannot ensure the width of the land surfaces of the hob. Moreover， each geometric feature of the hob has been produced through different manufacturing techniques and machine tools， which results in low efficiency. To solve this problem， we propose a semi-automatic computer aided design （CAD） method for hobs. The point clouds of each feature surface of a hob are calculated by combing mathematical equations of the top relief surfaces built by the proposed method with other existing equations of hob surfaces. According to the point clouds， the method can achieve the automatic modeling for the hob in three-dimensional （3D） software by classifying and extracting the parameter information of the feature-hierarchical knowledge of the hob. Based on the generated 3D model， the entire surfaces of the hob can be manufactured on a four-axis computer numerical control （CNC） milling machine through only twice clamping. Verification of the width of the land surface of the hob manufactured by semi-automatic CAD method on a measuring projector proved the precision of the designed width can be ensured. The edge of the contact area on the worm wheel in a meshing experiment is clear and distinct， which means the worm gear drive is meshed well and the hob manufactured by the proposed method has improved machinability. The method simplifies the processing technique， and improves the design efficiency and production accuracy.
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Clc Number:
TH132.4
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