Effect of the machining tolerances on the transmission error of planetary gearboxes: a numerical approach

Franco Concli

Bonfiglioli Mechatronic Research


The increasing demand for low-noise gearboxes has pointed out the importance to calculate the variation of the mesh stiffness which is the main source of excitation. The running noise, in fact, is the result of transmission errors which are generated by the varying stiffness. For this reason, in the years a lot of research was carried out by the different Standards Technical Committees to provide adequate calculation methods. Improvement of the gear quality helps to reduce noises, but even with a gear set of highest quality a transmission error exists.

In the standards the impact of the geometrical and dimensional tolerances of the other mechanical components such as shafts, housing etc., which can have a huge impact on the gear meshing stiffness variability is neglected.

A FEM based analysis of the influence of different geometrical errors on the static transmission error was carried out. From the study it was possible to extrapolate which tolerances have a more significant impact on the noise emission and which are less stringent. The aim was both to improve the acoustic behavior of the gearbox and to avoid expensive mechanical finishes where not needed.