Advantages in the production of power transmitting gears by fineblanking

Abstract

Fineblanking of gears has an enormous time and cost saving potential as well as the potential to significantly reduce CO2 emissions compared to conventional manufacturing of gears. Conventional manufacturing of gears consists of at least three steps such as milling, case hardening, and grinding. With fineblanking, only one manufacturing step is necessary. However, the load-carrying capacity regarding different gear fatigue failure modes, such as pitting or tooth root breakage, is stated significantly lower for the commonly used shear-cutting steels compared to the conventional case-hardened gears made out of high-strength hardened steels. This work shows the possibility of utilizing compressive residual stresses that are induced by the fineblanking process to increase the load-carrying capacity regarding tooth root breakage up to the level of case-carburized gears. Pinions and wheels made of S355MC (1.0976) and S500MC (1.0984) are fineblanked using parameters determined in previous works with a focus on the induction of high compressive residual stresses into the finished products. The variants are investigated regarding, e.g., cut surface characteristics, hardness, and residual stresses. For the two steels, as well as a stress relived variant, the tooth root bending strength is also determined in pulsator tests with the fineblanked pinions.