Tooth contact analysis of hypoid gear transmission prototypes manufacturing with vacuum casting methods

The article presents the experimental method of instantaneous contact area in hypoid gear transmission. The prototypes of hypoid gear have been made with one of the rapid prototyping method — Vacuum Casting process. This method permits to manufacture gear wheel with very complicated tooth profile in silicone tool (form or matrix) created in vacuum chamber with reduced pressure. Silicone matrix allows creating prototype in casting process or low pressure process. Silicone matrix has been made on the basis of gear transmission of car transmission system. Gears were made of transparent polymer materials to enable observation of the instantaneous contact area. The instantaneous contact area is that tooth flank surface area, which is in contact with mating surface of another tooth at a specific moment. Correct mating of gears and their kinematic precision depend on the shape and size of instantaneous contact area, as well as on changes during gear 's rotation. Contact between gear surfaces of geometrically ideal gearbox occurs at a point or line, but, because of a deformability of mating teeth flanks, in reality it is always a certain surface. The method of tooth contact area as described in the paper, permits a dynamic determination of the gearbox mating area. Existing experimental methods permit only a static observation of the mating area.