Radial oscillation: how to deal with noise problems in gears

Today we talk again about gear noise and we do it through radial oscillation. This is the radial position difference of a measuring ball between successive teeth. It means that during the control phase a reference axis is taken on which to detect different values of the various teeth. Consequently the difference between the major and minor value is called Fr and represents the total value of radial oscillation. In a very practical way, Fr is the position measurement of a control sphere inserted in each cavity of the tooth and represents the major difference. In fact, it is often also referred to as: eccentricity.

What causes and how do we manage Fr?

Radial oscillation is a gear defect and is caused by an off axis of the teeth. This in turn comes from manufacturing defects or errors or from deformations during heat treatment. As we anticipated, the Fr is closely related to noise phenomena. It therefore turns out to be a problem to be managed in many applications.

The runout Fr is a factor to be managed in the design phase. In fact, it is necessary to immediately check which is the maximum acceptable value for the specific application. As we said, based on the latter, the permissible value changes.

In general, among the many, the major cause of noise is Fr. To solve the problem, keep the value low.

If you are wondering why this defect is created, it is usually because an accurate technical analysis has not been carried out. As a consequence, it happens that a high Fr is created during the hobbing phase. Above all, when there is a off center between gripping the turned piece and the hobbing tool. To solve the problem, it is necessary to take care of the concentricity in the turning phase and check the tool during placement.

More rarely, the heat treatment following hobbing can lead to deformation of the Fr. Compared to the previous case, this can certainly be solved very quickly and cheaply by applying a teeth grinding phase after the treatment.

Have you ever had noise problems in your applications?