Page 188 of catalogue Super Precision Bearings of Schaeffler Technologies GmbH & Co. KG

Engineering
Speed dependent fits

Speed dependent fits
FAG Super precision bearings are suitable for the highest speeds. Speed indices of n · d m up to 2,0 · 10 6 mm/min are attainable with grease lubrication, while oil-lubricated bearings can attain speeds as high as 3,0 · 10 6 mm/min and beyond. Such high speeds cause high centrifugal forces which act on the inner rings and cause them to expand. This ring expansion leads to a lifting off of the inner ring from the shaft and thus to clearance between inner ring and shaft.

Possible results of this process are: • Fretting corrosion • Turning of the ring on the shaft • poor shaft support with increased tendency to vibration • reduced bearing performance due to possible misalignment. These effects can be avoided through a correspondingly tight fit on the shaft. The required interference can be obtained from Diagram 11 or calculated with the help of the BEARINX ® program. The values determined in this way yield a fit with a remaining interference of 1 μm at maximum speed.

High interference leads to an increase in preload, in particular in the case of rigid adjusted bearings. This in turn leads to increased heat generation in the bearing arrangement as well as losses in terms of speed-ability. This preload increase must be compensated by appropriate measures. With values fw · n2 1,2 (red zone in Diagram 11), it is advisable to consult the application engineering department of Schaeffler Group Industrial.

24 22 20 18 16 14 Interference 10 [μm] 10 8 6 4 2 0 0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 2,2 2,4 Hollow shaft 75 % Hollow shaft 50 % Solid shaft

n2 · f w

mm min2

3

11: Speed-dependent determination of interference shaft/inner ring

187

Engineering