Modelling of a Hobbing Tool Series for Generating Spur Gears with Circular Fillet

Andromachi N. Zouridaki


model development, spur gears, circular fillet, tooling optimisation


To increase the bending resistance of spur gear teeth it is customary to affect changes to the geometry of the gear pair. Changing the standard involute geometry of course leads to the deterioration of some of the performance characteristics of the pair such as increased sliding velocity, decreased contact ratio and decreased pitting resistance. Circular filleted teeth are composed of a standard involute working profile and a circular fillet at the root, instead of the standard trochoidal, thus offering lower stress concentration and increased bending strength without affecting the involute characteristics at all. However, these teeth are cut by hob cutters with different than standard tip geometry, hence each gear with a certain number of teeth requires its own cutter geometry. In this paper an optimised solution for a single cutting tool geometry to cut a range of different tooth sizes is sought in order to produce sturdier tooth fillets than the standard while keeping the tooling costs low.

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