Research On The Finishing Gear Hob Based On Line Contacting Conjugating Principle

It is a very important role that the cylindrical involute gears play in industry. Nowadays,hobbing is the most popular and economic gears fabricating method in modern gearproduction field. So, it’s obviously significant to carry research on promoting the precisionof hobbing. However, there’s unavoidable theoretical forming error in traditional hobs,owning to the reason that it often has to use instead worm to reduce the difficulties inmanufacturing, for example, relieving. What’ more, the hobbing method that the traditionalhobs based on is the enveloping generating principle, which limits the design of it in severalaspects and leads to the hardness to raise the cutting accuracy of hobs. This paper starts fromthe generating theory of the surface of gear tooth and carries much analysis on cuttingkinematics, applies the principle of line contact conjugating to gears hobbing and designand manufacturing a novel gear hob according to the generating line cutting method. Thisnovel hob has a simple structure and without forming error, so it can be easily fabricated andalso to ensure the manufacturing precision. Both of the cutting experiment and gear testingare carried on in this paper too, which demonstrated in practice that this hob can be used ontraditional gear hobbing machine in a very convenient way and obviously improves theprecision of gear. This paper mainly covers the following contents:(1) The gear precision machining methods are illustrated, showing that it’s of importantmeaning to promote the hobbing precision, such as, increase efficiency of production andreduce the cost in gear finishing field. The development and present situation of hobbing andhobs and their optimization are also systematically demonstrated. Then the research meaningand main contents of this paper are introduced.(1) The gear precision machining methods are illustrated, showing that it’s of importantmeaning to promote the hobbing precision, such as, increase efficiency of production andreduce the cost in gear finishing field. The development and present situation of hobbing andhobs and their optimization are also systematically demonstrated. Then the research meaningand main contents of this paper are introduced.(2) The generating principle of gear tooth surface is demonstrated as well as the basic principle that the traditional hobs based on. Then, the special cylindrical helical gear pair isintroduced, which with the assembly conditions that their base circle are tangent and theangle between their axles equals to the sum of their base helix angles, and its rightness iscertified. And in this process, the velocity along the generating line is also obtained. The linecontact conjugating principle is introduced and the structure of the basic worm of the novelhob is gained either. So, according to the research of the kinematics of the cutting edge of thegenerating surface, the cutting principle of this novel hob is deduced. Following that, theforming method of this hob and its basic structure is introduced. And then, some research ofthe hobbing process of this novel hob is carried on.(3) The detailed structure of the novel hob is designed, and its rightness is certified bythe three-dimensional modeling and kinematical simulation with computer. The process ofthe novel hob’s manufacturing is studied and the characteristics of the process, such as, easymanufacture and low cost, are illustrated.(4) The cutting experiment with this novel hob is carried on a traditional hobbingmachine and the gear cut by this hob is detected. The cutting process shows that the hob cutthe surface of gear tooth with line contacting and a bevel angle, and the whole processduration is smooth and without impact. The detect result shows that the novel hob can reallyraise the precision of gears with1~2degree.From the theory research, the structure design and its computer modeling and analysis,the manufacture process, the hobbing experiment and the detecting result illustrated in thispaper, the advantages of the novel hob is obvious: the configuration is simple and withouttheoretical error; it’s easy to manufacture and keep high precision; it’s convenient to use witha high production efficiency; it can significantly improve gears’ precision with a low cost. Soit is valuable to apply it to industry production.