High precision ball bearings - Spekuma Kullager AB

www.gmn.dePreloadRigid preload: Single bearingsBearing 1 Bearing 2Structural features:· Bearing 1 (work side) and bearing 2 have axially and radiallyfixed positions (inner rings sit firmly on the shaft and outer ringsin the housing)· The contact surfaces of associated components to the inner andouter ring have equal length and are plane parallel· To achieve the predefined preload, it is necessary for therespective bearings to be matchedCharacteristics:· Substantially increased axial and radial rigidity(in comparison to spring preload)· As friction heat increases as a consequence of increased speed,preload increases to reduce maximum speed(in comparison to spring preload)The theoretical maximum speed can be calculatedon the basis of speed correction factors· Temperature differences between shaft (inner ring) andhousing (outer ring) lead to preload changes due to thermalexpansionIf the shaft's temperature is higher than that of the housing,the bearing's radial clearance decreasesVery high temperature differences and small contact anglescan cause radial tension· With small bearing spacing, a temperature gradient fromshaft to housing causes an increase of preload· With large bearing spacing, a temperature gradient fromshaft to housing causes a decrease of preload· The change of preload under operating conditions mustbe considered in the designGMN provides software solutions to perform the complex calculationfor required bearing preload; these programs embody many yearsof practical experience which lead to reliable preload results.Rigid preload: Bearing setsMultiple arrangements of bearings to form bearing sets increaseload capacity, rigidity and lift-off force.Rigidity and lift-off forceRadial rigidity for all arrangements:at α = 15°: C rad ~ 6 · C axat α = 25°: C rad ~ 2 · C axBearing arrangement* Reference values for bearing pairs in O or X arrangement (see bearing data).Influences due to operating conditions (e.g. speed, load) are not taken into account.EffectiveNominal preloadAxial rigidityLift-off forceF V [N] C ax * [N/µm] F a max [N]< > or > < DB, DF F V C ax 2.85 · F V TBT 1.35 · F V 1.45 · C ax 5.65 · F V> QBC 2 · F V 2 · C ax 5.65 · F V