Macroeffect of microgeometry

The top priority of modern machine-building production is continuous monitoring of product quality, one of the most important parameter of which is microgeometry. Surface microirregularities formed during machining have a determining influence on the bearing operation in the future. Increased values of parameters such as roughness, profile, waviness and roundness lead to uneven wear of individual sections of the bearing and premature bearing failure.

The production laboratory of Baltic Bearing Company-Riga uses modern methodologies and instruments from leading manufacturers to control the parameters of surface microgeometry: roundness measurement device, roughness measuring instruments, profilometers, autocollimators, optimeters, three-dimensional measuring machines and other special equipment.

The operational properties and durability of assemble units equally depend not only on the condition of the working and mounting surfaces of the bearing, but also on the quality of the mounting surfaces of the units in which bearing is installed.

As an example, consider the effect of the roundness of gearbox mounting surfaces on the bearing quality.

The engineers of the Baltic Bearing Company-Riga needed to establish the reason of the increased noise and vibration level of the gearbox. The manufacturer of the gearbox found that the reason of noise and vibration problem were bearings. Analysis of rings, selected at random from a batch at the BBC-R production, showed that their microgeometric characteristics met specifications. That’s why it was an idea that the problem happens when bearing are mounting into the bore of the gearbox housing.

To confirm this theory, there were made measurements of the raceway roundness of BBC-R bearings before mounting into the gearbox, the mounting surfaces of the gearbox housing and the bearing raceways roundness during and after mounting.

The results showed that the values of the roundness of the gearbox housing mounting surfaces exceed the values normalized by the standard. This leads to changes in the form of bearing rings and an increasing of the raceway roundness in several times after bearing is mounted into the gearbox housing. As a result, noise and vibration of the assembled gearbox is increased.

The gearbox producer received recommendations from BBC-R engineers and made adjustments to the gearbox housing design, thereby eliminating the cause of the problem.
According to the statistics of Baltic Bearing Company-Riga, the main reasons for bearing failure are:

– installation errors;
– deviations of the installation unit;
– aggressive operating environment;
– incorrect selection of the bearing.

The engineers of the Baltic Bearing Company-Riga are ready to provide support to our customers on any issues related to the selection, installation and operation of bearings. BBC-R laboratory specialists will make researches and find the reasons of the problem.

Pic. 1 – Influence of the roundness of the gearbox mounting surface on the the roundness of the bearing
raceways:

A – Roundness of the bearing raceway before it pressed into the gearbox;

B – Roundness of the of the gearbox mounting surface;

C – Roundness of the raceway of installed bearing in the gearbox;

D – Roundness of the raceway of the bearing pressed out of the gearbox.