摘要：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 ***,each geometric feature of the hob has been produced through different manufacturing techniques and machine tools,which results in low *** solve this problem,we propose a semi-automatic co.puter aided design(CAD)method for *** point clouds of each feature surface of a hob are calculated by co.bing mathematical equations of the top relief surfaces built by the proposed method with other existing equations of hob *** 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 *** on the generated 3D model,the entire surfaces of the hob can be manufactured on a four-axis co.puter numerical co.trol(CNC)milling machine through only twice *** 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 *** edge of the co.tact 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 *** method simplifies the processing technique,and improves the design efficiency and production accuracy.