A five-axis CNC machining method of orthogonal variable transmission ratio face gear

Abstract

In order to verify the validity of the design for the orthogonal variable transmission ratio face gear pair, a five-axis CNC machine tool was used to machine this gear. The cutter tooth profile coordinate system, orthogonal variable ratio face gear machining coordinates, the model for the round-corner at tooth tip, the contact line model and CNC machining models were established by using space gear meshing theory and the machining principle of five-axis CNC machine tools. The method of machining this gear along the contact line has been obtained through the combination of the envelope method and milling principle. Cutter tooth profile equations, coordinate transformation matrices between the non-circular gear tooth surface and orthogonal variable transmission ratio gear tooth surface, transition surface equations and five-axis motion equations were derived. The rolling experiment and tooth surface measurement experiment were conducted on the gear, which was processed by a five-axis CNC machine. The results show that the tooth surface accuracy of the orthogonal variable transmission ratio face gear is high. The design of the orthogonal variable transmission ratio face gear, and its processing method using a five-axis NC machine have been verified.Key words : Face gear, CNC machining, Variable transmission ratio, Design, Drive IntroductionOrthogonal variable transmission ratio face gear drive is a gear drive where a non-circular gear and an orthogonal variable ratio face gear are engaged with a 90 degrees' intersecting axis. The orthogonal variable transmission ratio face gear combines the features of non-cylindrical gear and bevel gear and it allows variable transmission ratio between intersecting axis. The driving wheel is an on-cylindrical gear, and the driven one is a face gear. The gear pair can realize given variable transmission ratio. The Orthogonal variable transmission ratio face gear pair is shown in Figure1. In this research report, OVTR face gear is stand for orthogonal variable transmission ratio face gear. Fig. 1 OVTR face gear pairIn face gear drive, a cylindrical gear is engaged with a bevel gear (Litvin, et al., 1992). In 1940's, Buckingham introduced face gear in his book. Today, the face gear transmission structure is mainly used in the shunt transmission structure of the helicopter's main gear transmission system (George, 2002). Its narrow range of applications is attributed to reasons such as complexity of design, poor precision and difficulties in teeth grinding. the development and application of the face gear transmission.DARPA in the U.S. investigated the face gear transmission technique in TRP project, with the aim to apply this technique to the new generation Apache helicopter gunship. The study included the manufacturing and experiment of carburized face gear. Saga University in Japan used a large helical hob with less gear to machine face gear (Ohshima, et al., 2009). U.S. Processing and Treatment Center improved the hob and made it possible to process small face gears and imp...

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