Study On Spirac Machining Theory And Application Of Epicycloid Bevel And Hypoid Gears

Epicycloid bevel and hypoid gears are used in motion and power transmission between intersecting and crossed axes, respectively. They have the advantages of steady transmission, low noise, great carrying capacity, etc. Oerlikon’s Spirac cutting system is widely used due to its high cutting efficiency. As tooth contact pattern is an important assessment of meshing characteristics, its shape, size and position directly affect the transmission stability, noise behavior and carrying capacity of the gear set. In order to explore a more efficient processing method, this paper studies a meshing characteristics pre-controlling method of epicycloid bevel and hypoid gears, and proposes a new semi generating method based on gear plastic forming. The contents of the paper cover:(1) Study on Spirac cutting principle. This paper studies the blank geometrical parameter design of epicycloid bevel and hypoid gears, and based on the relationship of position and relative motion between the cutting tool, machine tool, work piece, establishes the Spirac mathematical model of machine tool setting and tooth contact analysis, which provides a theoretical basis for parameter optimization and further research on Spirac method.(2) Study on meshing characteristics pre-controlling method of epicycloid bevel and hypoid gears. This paper proposes a Spirac machine tool settings calculation method of predetermined contact pattern length which pre-controls the load carrying capability of the gear set through tilt angle modification controlling the length of the instant contact pattern, proposes a Spirac machine tool settings calculation method of predetermined contact path direction angle to make the contact paths on working and non-working flanks symmetric. On this basis, the paper proposes a Spirac machine tool settings calculation method of predetermined contact pattern length factor and contact path direction angle, which eliminates the edge contact, reduces the transmission noise and the error of transmission ratio, improves the motion stability and transmission precision, and achieves the consistency of forward and reverse driving of the gear set.(3) Study on digital tooth surface design and visual analysis. Based on the Spirac method, taking an epicycloid hypoid gear set as an example, this paper derives equations of the pinion and gear tooth surface, and builds the3D model of gear set. According to the characteristics analysis of tooth pitch, undercutting and shrinkage, and gear set interference analysis test, it verifies the correctness and practicability of the meshing characteristics pre-controlling methods.(4) Study on general NC machining technology. Taking an epicycloid hypoid gear set as an example, simulation and process development about digital models general NC machining are carried out on the basis of Spirac tooth surface generating method. It provides a general NC machining method of complying with the design parameters of the original drawings and the characteristic parameters obtained from Spirac cutting theory for a single piece or low-volume production of epicycloid bevel and hypoid gears.(5) A new semi generating cutting method based on gear plastic forming. This paper proposes a new semi generating cutting method of epicycloid bevel and hypoid gears of the pinion adopting a non-generating cutting method to continuous indexing cut and the gear adopting plastic forming. This paper builds a mathematical model of pinion machine tool setting and gear tooth surface generation, builds digital models of pinion and gear, and studies the rule of gear tooth surface modification. Taking an epicycloid hypoid gear set as an example, the feasibility of the new method is verified by tooth contact analysis and visual inspection. This method realizes high manufacturing efficiency of epicycloid bevel and hypoid gears.Based on gear plastic forming, this paper proposes a new semi generating cutting method, which extremely improves the manufacturing efficiency, and provides a theoretical basis for high-volume production of epicycloid bevel and hypoid gears. Based on meshing characteristics pre-controlling technology, it achieves the consistency of the forward and reverse driving of epicycloid bevel and hypoid gears. And based on general NC machining technology, it provides a cutting method for a single piece or low-volume production of epicycloid bevel and hypoid gears.