super precision bearings

Grease Distribution RunThe correct initial operation ofgrease-lubricated bearing arrangementshas a great influence on theperformance and service life of abearing arrangement. A start-stopoperation is recommended forgrease distribution. This preventsexcessively high damaging temperaturesin the contact area. Duringthe stop phase a temperature balancetakes place between the individualbearing components so thatdamaging preloading conditionsdo not occur. It is recommendedthat the temperature developmentduring the grease distribution runand the following continuous operationbe monitored by means ofa temperature sensor located asclose to the bearing outer ring aspossible. A progressive rise in temperaturethat occurs for instanceunder conditions of excessive preloading,must be avoided at allevents. The grease distribution iscomplete when a stable bearingtemperature has been reached. Formaximum speeds the run-in procedureshould be carried out at halfspeed initially, followed by a 0.75fold speed prior to operation atmaximum speed. Illustration 27shows recommendations for greasedistribution runs of open andsealed spindle bearings.The grease quantity, Table 25, andthe grease distribution run, Illustration27, are available as shrinkwrappedcards in DIN A5 formatfor use in workshops.The run-in procedure consists of several cycles of a start-stop operation with differing speeds and operatingperiods, the standstill periods after each run being particularly important. The required number of cycles maydiffer depending on bearing size, bearing number, maximum speeds and bearing environment.SpeedOperating and standstill periodsOperationStandstill0.5 · n max20 s 2 min Overall period 11 min 40 s0.75 · n max20 s 2 min Overall period 11 min 40 s20 s 2 min30 s 2 minn max1 min 1 min Overall period 56 min 40 sFurther cycles with extended operating periods and shorter standstill periods should be carried out untila steady-state temperature has been reached.Engineering27: Recommendations for grease distribution runs of open and sealed spindle bearingsFAG · 147