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The material of the wheel in a worm gear has to be nonrigid due to very high sliding velocity. Such gears are currently made of plastic in the case of a small module. The present paper describes an original method for studying the quasi-static loaded behavior of a worm gear, with a steel worm and a nylon wheel. Plastics are viscoelastic materials and do not obey Hooke’s law. This paper describes an elaborated method that is a generalization of Kelvin’s model. The computation also uses experimental tests to obtain data relating to the plastic. The computation of the load sharing is described and uses the equation of displacement compatibility. The history of previous deformation and the effect of the nylon’s structural damping are taken into account. At a given constant temperature, the load sharing, meshing stiffness, and loaded transmission error depend on the driving torque and time, that is to say speed of rotation.

International audienceThe design of spiral bevel gears remains complex since tooth geometry and the resulting kinematic performance stem directly from the manufacturing process. Spiral bevel gear cutting up to now has relied on the works of several manufacturers. Recent advances in milling machine technology and computer aided manufacturing (CAM) now make it possible to manufacture good quality spiral bevel gears on a standard 5-axis milling machine. This paper describes the computer aided design (CAD) definition and manufacturing of spiral bevel gear tooth surfaces. Process performance is assessed by comparing the resulting surfaces after machining with the predefined CAD surfaces. This manufacturing process makes it possible to obtain geometry analytically, making design easier than with standard spiral bevel gears